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9812 lines
281 KiB
9812 lines
281 KiB
# Calculate format=diff merge(sys-kernel/calculate-sources[fsync])!=
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From 4dc2913212c08c6970f6e8971fd23b6328982f94 Mon Sep 17 00:00:00 2001
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From: Piotr Gorski <lucjan.lucjanov@gmail.com>
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Date: Mon, 1 Nov 2021 12:11:04 +0100
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Subject: [PATCH] futex: resync from gitlab.collabora.com
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Signed-off-by: Piotr Gorski <lucjan.lucjanov@gmail.com>
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---
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Documentation/userspace-api/futex2.rst | 86 +
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Documentation/userspace-api/index.rst | 1 +
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MAINTAINERS | 3 +-
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arch/arm/tools/syscall.tbl | 1 +
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arch/arm64/include/asm/unistd.h | 2 +-
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arch/arm64/include/asm/unistd32.h | 2 +
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arch/x86/entry/syscalls/syscall_32.tbl | 1 +
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arch/x86/entry/syscalls/syscall_64.tbl | 1 +
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include/linux/syscalls.h | 7 +-
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include/uapi/asm-generic/unistd.h | 5 +-
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include/uapi/linux/futex.h | 25 +
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kernel/Makefile | 2 +-
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kernel/futex.c | 4272 -----------------
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kernel/futex/Makefile | 3 +
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kernel/futex/core.c | 1176 +++++
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kernel/futex/futex.h | 295 ++
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kernel/futex/pi.c | 1233 +++++
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kernel/futex/requeue.c | 897 ++++
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kernel/futex/syscalls.c | 396 ++
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kernel/futex/waitwake.c | 708 +++
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kernel/sys_ni.c | 3 +-
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.../selftests/futex/functional/.gitignore | 1 +
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.../selftests/futex/functional/Makefile | 3 +-
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.../futex/functional/futex_wait_timeout.c | 21 +-
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.../futex/functional/futex_wait_wouldblock.c | 41 +-
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.../selftests/futex/functional/futex_waitv.c | 237 +
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.../testing/selftests/futex/functional/run.sh | 3 +
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.../selftests/futex/include/futex2test.h | 22 +
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28 files changed, 5163 insertions(+), 4284 deletions(-)
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create mode 100644 Documentation/userspace-api/futex2.rst
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delete mode 100644 kernel/futex.c
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create mode 100644 kernel/futex/Makefile
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create mode 100644 kernel/futex/core.c
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create mode 100644 kernel/futex/futex.h
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create mode 100644 kernel/futex/pi.c
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create mode 100644 kernel/futex/requeue.c
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create mode 100644 kernel/futex/syscalls.c
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create mode 100644 kernel/futex/waitwake.c
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create mode 100644 tools/testing/selftests/futex/functional/futex_waitv.c
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create mode 100644 tools/testing/selftests/futex/include/futex2test.h
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diff --git a/Documentation/userspace-api/futex2.rst b/Documentation/userspace-api/futex2.rst
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new file mode 100644
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index 000000000..7d37409df
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--- /dev/null
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+++ b/Documentation/userspace-api/futex2.rst
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@@ -0,0 +1,86 @@
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+.. SPDX-License-Identifier: GPL-2.0
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+
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+======
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+futex2
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+======
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+
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+:Author: André Almeida <andrealmeid@collabora.com>
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+
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+futex, or fast user mutex, is a set of syscalls to allow userspace to create
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+performant synchronization mechanisms, such as mutexes, semaphores and
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+conditional variables in userspace. C standard libraries, like glibc, uses it
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+as a means to implement more high level interfaces like pthreads.
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+
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+futex2 is a followup version of the initial futex syscall, designed to overcome
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+limitations of the original interface.
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+
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+User API
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+========
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+
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+``futex_waitv()``
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+-----------------
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+
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+Wait on an array of futexes, wake on any::
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+
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+ futex_waitv(struct futex_waitv *waiters, unsigned int nr_futexes,
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+ unsigned int flags, struct timespec *timeout, clockid_t clockid)
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+
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+ struct futex_waitv {
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+ __u64 val;
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+ __u64 uaddr;
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+ __u32 flags;
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+ __u32 __reserved;
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+ };
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+
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+Userspace sets an array of struct futex_waitv (up to a max of 128 entries),
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+using ``uaddr`` for the address to wait for, ``val`` for the expected value
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+and ``flags`` to specify the type (e.g. private) and size of futex.
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+``__reserved`` needs to be 0, but it can be used for future extension. The
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+pointer for the first item of the array is passed as ``waiters``. An invalid
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+address for ``waiters`` or for any ``uaddr`` returns ``-EFAULT``.
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+
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+If userspace has 32-bit pointers, it should do a explicit cast to make sure
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+the upper bits are zeroed. ``uintptr_t`` does the tricky and it works for
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+both 32/64-bit pointers.
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+
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+``nr_futexes`` specifies the size of the array. Numbers out of [1, 128]
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+interval will make the syscall return ``-EINVAL``.
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+
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+The ``flags`` argument of the syscall needs to be 0, but it can be used for
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+future extension.
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+
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+For each entry in ``waiters`` array, the current value at ``uaddr`` is compared
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+to ``val``. If it's different, the syscall undo all the work done so far and
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+return ``-EAGAIN``. If all tests and verifications succeeds, syscall waits until
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+one of the following happens:
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+
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+- The timeout expires, returning ``-ETIMEOUT``.
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+- A signal was sent to the sleeping task, returning ``-ERESTARTSYS``.
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+- Some futex at the list was awaken, returning the index of some waked futex.
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+
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+An example of how to use the interface can be found at ``tools/testing/selftests/futex/functional/futex_waitv.c``.
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+
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+Timeout
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+-------
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+
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+``struct timespec *timeout`` argument is an optional argument that points to an
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+absolute timeout. You need to specify the type of clock being used at
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+``clockid`` argument. ``CLOCK_MONOTONIC`` and ``CLOCK_REALTIME`` are supported.
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+This syscall accepts only 64bit timespec structs.
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+
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+Types of futex
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+--------------
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+
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+A futex can be either private or shared. Private is used for processes that
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+shares the same memory space and the virtual address of the futex will be the
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+same for all processes. This allows for optimizations in the kernel. To use
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+private futexes, it's necessary to specify ``FUTEX_PRIVATE_FLAG`` in the futex
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+flag. For processes that doesn't share the same memory space and therefore can
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+have different virtual addresses for the same futex (using, for instance, a
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+file-backed shared memory) requires different internal mechanisms to be get
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+properly enqueued. This is the default behavior, and it works with both private
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+and shared futexes.
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+
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+Futexes can be of different sizes: 8, 16, 32 or 64 bits. Currently, the only
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+supported one is 32 bit sized futex, and it need to be specified using
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+``FUTEX_32`` flag.
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diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst
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index c432be070..a61eac0c7 100644
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--- a/Documentation/userspace-api/index.rst
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+++ b/Documentation/userspace-api/index.rst
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@@ -28,6 +28,7 @@ place where this information is gathered.
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media/index
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sysfs-platform_profile
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vduse
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+ futex2
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.. only:: subproject and html
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diff --git a/MAINTAINERS b/MAINTAINERS
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index 3b79fd441..dd165835f 100644
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--- a/MAINTAINERS
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+++ b/MAINTAINERS
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@@ -7737,6 +7737,7 @@ M: Ingo Molnar <mingo@redhat.com>
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R: Peter Zijlstra <peterz@infradead.org>
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R: Darren Hart <dvhart@infradead.org>
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R: Davidlohr Bueso <dave@stgolabs.net>
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+R: André Almeida <andrealmeid@collabora.com>
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L: linux-kernel@vger.kernel.org
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S: Maintained
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T: git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking/core
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@@ -7744,7 +7745,7 @@ F: Documentation/locking/*futex*
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F: include/asm-generic/futex.h
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F: include/linux/futex.h
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F: include/uapi/linux/futex.h
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-F: kernel/futex.c
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+F: kernel/futex/*
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F: tools/perf/bench/futex*
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F: tools/testing/selftests/futex/
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diff --git a/arch/arm/tools/syscall.tbl b/arch/arm/tools/syscall.tbl
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index e842209e1..543100151 100644
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--- a/arch/arm/tools/syscall.tbl
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+++ b/arch/arm/tools/syscall.tbl
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@@ -462,3 +462,4 @@
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446 common landlock_restrict_self sys_landlock_restrict_self
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# 447 reserved for memfd_secret
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448 common process_mrelease sys_process_mrelease
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+449 common futex_waitv sys_futex_waitv
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diff --git a/arch/arm64/include/asm/unistd.h b/arch/arm64/include/asm/unistd.h
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index 3cb206aea..6bdb5f5db 100644
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--- a/arch/arm64/include/asm/unistd.h
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+++ b/arch/arm64/include/asm/unistd.h
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@@ -38,7 +38,7 @@
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#define __ARM_NR_compat_set_tls (__ARM_NR_COMPAT_BASE + 5)
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#define __ARM_NR_COMPAT_END (__ARM_NR_COMPAT_BASE + 0x800)
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-#define __NR_compat_syscalls 449
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+#define __NR_compat_syscalls 450
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#endif
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#define __ARCH_WANT_SYS_CLONE
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diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h
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index 844f6ae58..41ea1195e 100644
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--- a/arch/arm64/include/asm/unistd32.h
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+++ b/arch/arm64/include/asm/unistd32.h
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@@ -903,6 +903,8 @@ __SYSCALL(__NR_landlock_add_rule, sys_landlock_add_rule)
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__SYSCALL(__NR_landlock_restrict_self, sys_landlock_restrict_self)
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#define __NR_process_mrelease 448
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__SYSCALL(__NR_process_mrelease, sys_process_mrelease)
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+#define __NR_futex_waitv 449
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+__SYSCALL(__NR_futex_waitv, sys_futex_waitv)
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/*
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* Please add new compat syscalls above this comment and update
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diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
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index 960a021d5..7e2554369 100644
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--- a/arch/x86/entry/syscalls/syscall_32.tbl
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+++ b/arch/x86/entry/syscalls/syscall_32.tbl
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@@ -453,3 +453,4 @@
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446 i386 landlock_restrict_self sys_landlock_restrict_self
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447 i386 memfd_secret sys_memfd_secret
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448 i386 process_mrelease sys_process_mrelease
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+449 i386 futex_waitv sys_futex_waitv
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diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
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index 18b5500ea..fe8f8dd15 100644
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--- a/arch/x86/entry/syscalls/syscall_64.tbl
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+++ b/arch/x86/entry/syscalls/syscall_64.tbl
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@@ -370,6 +370,7 @@
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446 common landlock_restrict_self sys_landlock_restrict_self
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447 common memfd_secret sys_memfd_secret
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448 common process_mrelease sys_process_mrelease
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+449 common futex_waitv sys_futex_waitv
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#
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# Due to a historical design error, certain syscalls are numbered differently
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diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
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index 252243c77..528a478db 100644
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--- a/include/linux/syscalls.h
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+++ b/include/linux/syscalls.h
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@@ -58,6 +58,7 @@ struct mq_attr;
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struct compat_stat;
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struct old_timeval32;
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struct robust_list_head;
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+struct futex_waitv;
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struct getcpu_cache;
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struct old_linux_dirent;
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struct perf_event_attr;
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@@ -610,7 +611,7 @@ asmlinkage long sys_waitid(int which, pid_t pid,
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asmlinkage long sys_set_tid_address(int __user *tidptr);
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asmlinkage long sys_unshare(unsigned long unshare_flags);
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-/* kernel/futex.c */
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+/* kernel/futex/syscalls.c */
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asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
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const struct __kernel_timespec __user *utime,
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u32 __user *uaddr2, u32 val3);
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@@ -623,6 +624,10 @@ asmlinkage long sys_get_robust_list(int pid,
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asmlinkage long sys_set_robust_list(struct robust_list_head __user *head,
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size_t len);
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+asmlinkage long sys_futex_waitv(struct futex_waitv *waiters,
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+ unsigned int nr_futexes, unsigned int flags,
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+ struct __kernel_timespec __user *timeout, clockid_t clockid);
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+
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/* kernel/hrtimer.c */
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asmlinkage long sys_nanosleep(struct __kernel_timespec __user *rqtp,
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struct __kernel_timespec __user *rmtp);
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diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
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index 1c5fb86d4..4557a8b60 100644
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--- a/include/uapi/asm-generic/unistd.h
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+++ b/include/uapi/asm-generic/unistd.h
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@@ -880,8 +880,11 @@ __SYSCALL(__NR_memfd_secret, sys_memfd_secret)
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#define __NR_process_mrelease 448
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__SYSCALL(__NR_process_mrelease, sys_process_mrelease)
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+#define __NR_futex_waitv 449
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+__SYSCALL(__NR_futex_waitv, sys_futex_waitv)
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+
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#undef __NR_syscalls
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-#define __NR_syscalls 449
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+#define __NR_syscalls 450
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/*
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* 32 bit systems traditionally used different
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diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h
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index 235e5b2fa..71a5df8d2 100644
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--- a/include/uapi/linux/futex.h
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+++ b/include/uapi/linux/futex.h
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@@ -43,6 +43,31 @@
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#define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \
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FUTEX_PRIVATE_FLAG)
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+/*
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+ * Flags to specify the bit length of the futex word for futex2 syscalls.
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+ * Currently, only 32 is supported.
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+ */
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+#define FUTEX_32 2
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+
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+/*
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+ * Max numbers of elements in a futex_waitv array
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+ */
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+#define FUTEX_WAITV_MAX 128
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+
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+/**
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+ * struct futex_waitv - A waiter for vectorized wait
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+ * @val: Expected value at uaddr
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+ * @uaddr: User address to wait on
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+ * @flags: Flags for this waiter
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+ * @__reserved: Reserved member to preserve data alignment. Should be 0.
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+ */
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+struct futex_waitv {
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+ __u64 val;
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+ __u64 uaddr;
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+ __u32 flags;
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+ __u32 __reserved;
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+};
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+
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/*
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* Support for robust futexes: the kernel cleans up held futexes at
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* thread exit time.
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diff --git a/kernel/Makefile b/kernel/Makefile
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index 4df609be4..3f6ab5d50 100644
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--- a/kernel/Makefile
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+++ b/kernel/Makefile
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@@ -59,7 +59,7 @@ obj-$(CONFIG_FREEZER) += freezer.o
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obj-$(CONFIG_PROFILING) += profile.o
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obj-$(CONFIG_STACKTRACE) += stacktrace.o
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obj-y += time/
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-obj-$(CONFIG_FUTEX) += futex.o
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+obj-$(CONFIG_FUTEX) += futex/
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obj-$(CONFIG_GENERIC_ISA_DMA) += dma.o
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obj-$(CONFIG_SMP) += smp.o
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ifneq ($(CONFIG_SMP),y)
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diff --git a/kernel/futex.c b/kernel/futex.c
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deleted file mode 100644
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index c15ad276f..000000000
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--- a/kernel/futex.c
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+++ /dev/null
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@@ -1,4272 +0,0 @@
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-// SPDX-License-Identifier: GPL-2.0-or-later
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-/*
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- * Fast Userspace Mutexes (which I call "Futexes!").
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- * (C) Rusty Russell, IBM 2002
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- *
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- * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
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- * (C) Copyright 2003 Red Hat Inc, All Rights Reserved
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- *
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- * Removed page pinning, fix privately mapped COW pages and other cleanups
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- * (C) Copyright 2003, 2004 Jamie Lokier
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- *
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- * Robust futex support started by Ingo Molnar
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- * (C) Copyright 2006 Red Hat Inc, All Rights Reserved
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- * Thanks to Thomas Gleixner for suggestions, analysis and fixes.
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- *
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- * PI-futex support started by Ingo Molnar and Thomas Gleixner
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- * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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- * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
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- *
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- * PRIVATE futexes by Eric Dumazet
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- * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
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- *
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- * Requeue-PI support by Darren Hart <dvhltc@us.ibm.com>
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- * Copyright (C) IBM Corporation, 2009
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- * Thanks to Thomas Gleixner for conceptual design and careful reviews.
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- *
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- * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
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- * enough at me, Linus for the original (flawed) idea, Matthew
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- * Kirkwood for proof-of-concept implementation.
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- *
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- * "The futexes are also cursed."
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- * "But they come in a choice of three flavours!"
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- */
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-#include <linux/compat.h>
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-#include <linux/jhash.h>
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-#include <linux/pagemap.h>
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-#include <linux/syscalls.h>
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-#include <linux/freezer.h>
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-#include <linux/memblock.h>
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-#include <linux/fault-inject.h>
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-#include <linux/time_namespace.h>
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-
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-#include <asm/futex.h>
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-
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-#include "locking/rtmutex_common.h"
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-
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-/*
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|
- * READ this before attempting to hack on futexes!
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|
- *
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|
- * Basic futex operation and ordering guarantees
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|
- * =============================================
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|
- *
|
|
- * The waiter reads the futex value in user space and calls
|
|
- * futex_wait(). This function computes the hash bucket and acquires
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- * the hash bucket lock. After that it reads the futex user space value
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- * again and verifies that the data has not changed. If it has not changed
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- * it enqueues itself into the hash bucket, releases the hash bucket lock
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|
- * and schedules.
|
|
- *
|
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- * The waker side modifies the user space value of the futex and calls
|
|
- * futex_wake(). This function computes the hash bucket and acquires the
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- * hash bucket lock. Then it looks for waiters on that futex in the hash
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- * bucket and wakes them.
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|
- *
|
|
- * In futex wake up scenarios where no tasks are blocked on a futex, taking
|
|
- * the hb spinlock can be avoided and simply return. In order for this
|
|
- * optimization to work, ordering guarantees must exist so that the waiter
|
|
- * being added to the list is acknowledged when the list is concurrently being
|
|
- * checked by the waker, avoiding scenarios like the following:
|
|
- *
|
|
- * CPU 0 CPU 1
|
|
- * val = *futex;
|
|
- * sys_futex(WAIT, futex, val);
|
|
- * futex_wait(futex, val);
|
|
- * uval = *futex;
|
|
- * *futex = newval;
|
|
- * sys_futex(WAKE, futex);
|
|
- * futex_wake(futex);
|
|
- * if (queue_empty())
|
|
- * return;
|
|
- * if (uval == val)
|
|
- * lock(hash_bucket(futex));
|
|
- * queue();
|
|
- * unlock(hash_bucket(futex));
|
|
- * schedule();
|
|
- *
|
|
- * This would cause the waiter on CPU 0 to wait forever because it
|
|
- * missed the transition of the user space value from val to newval
|
|
- * and the waker did not find the waiter in the hash bucket queue.
|
|
- *
|
|
- * The correct serialization ensures that a waiter either observes
|
|
- * the changed user space value before blocking or is woken by a
|
|
- * concurrent waker:
|
|
- *
|
|
- * CPU 0 CPU 1
|
|
- * val = *futex;
|
|
- * sys_futex(WAIT, futex, val);
|
|
- * futex_wait(futex, val);
|
|
- *
|
|
- * waiters++; (a)
|
|
- * smp_mb(); (A) <-- paired with -.
|
|
- * |
|
|
- * lock(hash_bucket(futex)); |
|
|
- * |
|
|
- * uval = *futex; |
|
|
- * | *futex = newval;
|
|
- * | sys_futex(WAKE, futex);
|
|
- * | futex_wake(futex);
|
|
- * |
|
|
- * `--------> smp_mb(); (B)
|
|
- * if (uval == val)
|
|
- * queue();
|
|
- * unlock(hash_bucket(futex));
|
|
- * schedule(); if (waiters)
|
|
- * lock(hash_bucket(futex));
|
|
- * else wake_waiters(futex);
|
|
- * waiters--; (b) unlock(hash_bucket(futex));
|
|
- *
|
|
- * Where (A) orders the waiters increment and the futex value read through
|
|
- * atomic operations (see hb_waiters_inc) and where (B) orders the write
|
|
- * to futex and the waiters read (see hb_waiters_pending()).
|
|
- *
|
|
- * This yields the following case (where X:=waiters, Y:=futex):
|
|
- *
|
|
- * X = Y = 0
|
|
- *
|
|
- * w[X]=1 w[Y]=1
|
|
- * MB MB
|
|
- * r[Y]=y r[X]=x
|
|
- *
|
|
- * Which guarantees that x==0 && y==0 is impossible; which translates back into
|
|
- * the guarantee that we cannot both miss the futex variable change and the
|
|
- * enqueue.
|
|
- *
|
|
- * Note that a new waiter is accounted for in (a) even when it is possible that
|
|
- * the wait call can return error, in which case we backtrack from it in (b).
|
|
- * Refer to the comment in queue_lock().
|
|
- *
|
|
- * Similarly, in order to account for waiters being requeued on another
|
|
- * address we always increment the waiters for the destination bucket before
|
|
- * acquiring the lock. It then decrements them again after releasing it -
|
|
- * the code that actually moves the futex(es) between hash buckets (requeue_futex)
|
|
- * will do the additional required waiter count housekeeping. This is done for
|
|
- * double_lock_hb() and double_unlock_hb(), respectively.
|
|
- */
|
|
-
|
|
-#ifdef CONFIG_HAVE_FUTEX_CMPXCHG
|
|
-#define futex_cmpxchg_enabled 1
|
|
-#else
|
|
-static int __read_mostly futex_cmpxchg_enabled;
|
|
-#endif
|
|
-
|
|
-/*
|
|
- * Futex flags used to encode options to functions and preserve them across
|
|
- * restarts.
|
|
- */
|
|
-#ifdef CONFIG_MMU
|
|
-# define FLAGS_SHARED 0x01
|
|
-#else
|
|
-/*
|
|
- * NOMMU does not have per process address space. Let the compiler optimize
|
|
- * code away.
|
|
- */
|
|
-# define FLAGS_SHARED 0x00
|
|
-#endif
|
|
-#define FLAGS_CLOCKRT 0x02
|
|
-#define FLAGS_HAS_TIMEOUT 0x04
|
|
-
|
|
-/*
|
|
- * Priority Inheritance state:
|
|
- */
|
|
-struct futex_pi_state {
|
|
- /*
|
|
- * list of 'owned' pi_state instances - these have to be
|
|
- * cleaned up in do_exit() if the task exits prematurely:
|
|
- */
|
|
- struct list_head list;
|
|
-
|
|
- /*
|
|
- * The PI object:
|
|
- */
|
|
- struct rt_mutex_base pi_mutex;
|
|
-
|
|
- struct task_struct *owner;
|
|
- refcount_t refcount;
|
|
-
|
|
- union futex_key key;
|
|
-} __randomize_layout;
|
|
-
|
|
-/**
|
|
- * struct futex_q - The hashed futex queue entry, one per waiting task
|
|
- * @list: priority-sorted list of tasks waiting on this futex
|
|
- * @task: the task waiting on the futex
|
|
- * @lock_ptr: the hash bucket lock
|
|
- * @key: the key the futex is hashed on
|
|
- * @pi_state: optional priority inheritance state
|
|
- * @rt_waiter: rt_waiter storage for use with requeue_pi
|
|
- * @requeue_pi_key: the requeue_pi target futex key
|
|
- * @bitset: bitset for the optional bitmasked wakeup
|
|
- * @requeue_state: State field for futex_requeue_pi()
|
|
- * @requeue_wait: RCU wait for futex_requeue_pi() (RT only)
|
|
- *
|
|
- * We use this hashed waitqueue, instead of a normal wait_queue_entry_t, so
|
|
- * we can wake only the relevant ones (hashed queues may be shared).
|
|
- *
|
|
- * A futex_q has a woken state, just like tasks have TASK_RUNNING.
|
|
- * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
|
|
- * The order of wakeup is always to make the first condition true, then
|
|
- * the second.
|
|
- *
|
|
- * PI futexes are typically woken before they are removed from the hash list via
|
|
- * the rt_mutex code. See unqueue_me_pi().
|
|
- */
|
|
-struct futex_q {
|
|
- struct plist_node list;
|
|
-
|
|
- struct task_struct *task;
|
|
- spinlock_t *lock_ptr;
|
|
- union futex_key key;
|
|
- struct futex_pi_state *pi_state;
|
|
- struct rt_mutex_waiter *rt_waiter;
|
|
- union futex_key *requeue_pi_key;
|
|
- u32 bitset;
|
|
- atomic_t requeue_state;
|
|
-#ifdef CONFIG_PREEMPT_RT
|
|
- struct rcuwait requeue_wait;
|
|
-#endif
|
|
-} __randomize_layout;
|
|
-
|
|
-/*
|
|
- * On PREEMPT_RT, the hash bucket lock is a 'sleeping' spinlock with an
|
|
- * underlying rtmutex. The task which is about to be requeued could have
|
|
- * just woken up (timeout, signal). After the wake up the task has to
|
|
- * acquire hash bucket lock, which is held by the requeue code. As a task
|
|
- * can only be blocked on _ONE_ rtmutex at a time, the proxy lock blocking
|
|
- * and the hash bucket lock blocking would collide and corrupt state.
|
|
- *
|
|
- * On !PREEMPT_RT this is not a problem and everything could be serialized
|
|
- * on hash bucket lock, but aside of having the benefit of common code,
|
|
- * this allows to avoid doing the requeue when the task is already on the
|
|
- * way out and taking the hash bucket lock of the original uaddr1 when the
|
|
- * requeue has been completed.
|
|
- *
|
|
- * The following state transitions are valid:
|
|
- *
|
|
- * On the waiter side:
|
|
- * Q_REQUEUE_PI_NONE -> Q_REQUEUE_PI_IGNORE
|
|
- * Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_WAIT
|
|
- *
|
|
- * On the requeue side:
|
|
- * Q_REQUEUE_PI_NONE -> Q_REQUEUE_PI_INPROGRESS
|
|
- * Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_DONE/LOCKED
|
|
- * Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_NONE (requeue failed)
|
|
- * Q_REQUEUE_PI_WAIT -> Q_REQUEUE_PI_DONE/LOCKED
|
|
- * Q_REQUEUE_PI_WAIT -> Q_REQUEUE_PI_IGNORE (requeue failed)
|
|
- *
|
|
- * The requeue side ignores a waiter with state Q_REQUEUE_PI_IGNORE as this
|
|
- * signals that the waiter is already on the way out. It also means that
|
|
- * the waiter is still on the 'wait' futex, i.e. uaddr1.
|
|
- *
|
|
- * The waiter side signals early wakeup to the requeue side either through
|
|
- * setting state to Q_REQUEUE_PI_IGNORE or to Q_REQUEUE_PI_WAIT depending
|
|
- * on the current state. In case of Q_REQUEUE_PI_IGNORE it can immediately
|
|
- * proceed to take the hash bucket lock of uaddr1. If it set state to WAIT,
|
|
- * which means the wakeup is interleaving with a requeue in progress it has
|
|
- * to wait for the requeue side to change the state. Either to DONE/LOCKED
|
|
- * or to IGNORE. DONE/LOCKED means the waiter q is now on the uaddr2 futex
|
|
- * and either blocked (DONE) or has acquired it (LOCKED). IGNORE is set by
|
|
- * the requeue side when the requeue attempt failed via deadlock detection
|
|
- * and therefore the waiter q is still on the uaddr1 futex.
|
|
- */
|
|
-enum {
|
|
- Q_REQUEUE_PI_NONE = 0,
|
|
- Q_REQUEUE_PI_IGNORE,
|
|
- Q_REQUEUE_PI_IN_PROGRESS,
|
|
- Q_REQUEUE_PI_WAIT,
|
|
- Q_REQUEUE_PI_DONE,
|
|
- Q_REQUEUE_PI_LOCKED,
|
|
-};
|
|
-
|
|
-static const struct futex_q futex_q_init = {
|
|
- /* list gets initialized in queue_me()*/
|
|
- .key = FUTEX_KEY_INIT,
|
|
- .bitset = FUTEX_BITSET_MATCH_ANY,
|
|
- .requeue_state = ATOMIC_INIT(Q_REQUEUE_PI_NONE),
|
|
-};
|
|
-
|
|
-/*
|
|
- * Hash buckets are shared by all the futex_keys that hash to the same
|
|
- * location. Each key may have multiple futex_q structures, one for each task
|
|
- * waiting on a futex.
|
|
- */
|
|
-struct futex_hash_bucket {
|
|
- atomic_t waiters;
|
|
- spinlock_t lock;
|
|
- struct plist_head chain;
|
|
-} ____cacheline_aligned_in_smp;
|
|
-
|
|
-/*
|
|
- * The base of the bucket array and its size are always used together
|
|
- * (after initialization only in hash_futex()), so ensure that they
|
|
- * reside in the same cacheline.
|
|
- */
|
|
-static struct {
|
|
- struct futex_hash_bucket *queues;
|
|
- unsigned long hashsize;
|
|
-} __futex_data __read_mostly __aligned(2*sizeof(long));
|
|
-#define futex_queues (__futex_data.queues)
|
|
-#define futex_hashsize (__futex_data.hashsize)
|
|
-
|
|
-
|
|
-/*
|
|
- * Fault injections for futexes.
|
|
- */
|
|
-#ifdef CONFIG_FAIL_FUTEX
|
|
-
|
|
-static struct {
|
|
- struct fault_attr attr;
|
|
-
|
|
- bool ignore_private;
|
|
-} fail_futex = {
|
|
- .attr = FAULT_ATTR_INITIALIZER,
|
|
- .ignore_private = false,
|
|
-};
|
|
-
|
|
-static int __init setup_fail_futex(char *str)
|
|
-{
|
|
- return setup_fault_attr(&fail_futex.attr, str);
|
|
-}
|
|
-__setup("fail_futex=", setup_fail_futex);
|
|
-
|
|
-static bool should_fail_futex(bool fshared)
|
|
-{
|
|
- if (fail_futex.ignore_private && !fshared)
|
|
- return false;
|
|
-
|
|
- return should_fail(&fail_futex.attr, 1);
|
|
-}
|
|
-
|
|
-#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
|
|
-
|
|
-static int __init fail_futex_debugfs(void)
|
|
-{
|
|
- umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
|
|
- struct dentry *dir;
|
|
-
|
|
- dir = fault_create_debugfs_attr("fail_futex", NULL,
|
|
- &fail_futex.attr);
|
|
- if (IS_ERR(dir))
|
|
- return PTR_ERR(dir);
|
|
-
|
|
- debugfs_create_bool("ignore-private", mode, dir,
|
|
- &fail_futex.ignore_private);
|
|
- return 0;
|
|
-}
|
|
-
|
|
-late_initcall(fail_futex_debugfs);
|
|
-
|
|
-#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
|
|
-
|
|
-#else
|
|
-static inline bool should_fail_futex(bool fshared)
|
|
-{
|
|
- return false;
|
|
-}
|
|
-#endif /* CONFIG_FAIL_FUTEX */
|
|
-
|
|
-#ifdef CONFIG_COMPAT
|
|
-static void compat_exit_robust_list(struct task_struct *curr);
|
|
-#endif
|
|
-
|
|
-/*
|
|
- * Reflects a new waiter being added to the waitqueue.
|
|
- */
|
|
-static inline void hb_waiters_inc(struct futex_hash_bucket *hb)
|
|
-{
|
|
-#ifdef CONFIG_SMP
|
|
- atomic_inc(&hb->waiters);
|
|
- /*
|
|
- * Full barrier (A), see the ordering comment above.
|
|
- */
|
|
- smp_mb__after_atomic();
|
|
-#endif
|
|
-}
|
|
-
|
|
-/*
|
|
- * Reflects a waiter being removed from the waitqueue by wakeup
|
|
- * paths.
|
|
- */
|
|
-static inline void hb_waiters_dec(struct futex_hash_bucket *hb)
|
|
-{
|
|
-#ifdef CONFIG_SMP
|
|
- atomic_dec(&hb->waiters);
|
|
-#endif
|
|
-}
|
|
-
|
|
-static inline int hb_waiters_pending(struct futex_hash_bucket *hb)
|
|
-{
|
|
-#ifdef CONFIG_SMP
|
|
- /*
|
|
- * Full barrier (B), see the ordering comment above.
|
|
- */
|
|
- smp_mb();
|
|
- return atomic_read(&hb->waiters);
|
|
-#else
|
|
- return 1;
|
|
-#endif
|
|
-}
|
|
-
|
|
-/**
|
|
- * hash_futex - Return the hash bucket in the global hash
|
|
- * @key: Pointer to the futex key for which the hash is calculated
|
|
- *
|
|
- * We hash on the keys returned from get_futex_key (see below) and return the
|
|
- * corresponding hash bucket in the global hash.
|
|
- */
|
|
-static struct futex_hash_bucket *hash_futex(union futex_key *key)
|
|
-{
|
|
- u32 hash = jhash2((u32 *)key, offsetof(typeof(*key), both.offset) / 4,
|
|
- key->both.offset);
|
|
-
|
|
- return &futex_queues[hash & (futex_hashsize - 1)];
|
|
-}
|
|
-
|
|
-
|
|
-/**
|
|
- * match_futex - Check whether two futex keys are equal
|
|
- * @key1: Pointer to key1
|
|
- * @key2: Pointer to key2
|
|
- *
|
|
- * Return 1 if two futex_keys are equal, 0 otherwise.
|
|
- */
|
|
-static inline int match_futex(union futex_key *key1, union futex_key *key2)
|
|
-{
|
|
- return (key1 && key2
|
|
- && key1->both.word == key2->both.word
|
|
- && key1->both.ptr == key2->both.ptr
|
|
- && key1->both.offset == key2->both.offset);
|
|
-}
|
|
-
|
|
-enum futex_access {
|
|
- FUTEX_READ,
|
|
- FUTEX_WRITE
|
|
-};
|
|
-
|
|
-/**
|
|
- * futex_setup_timer - set up the sleeping hrtimer.
|
|
- * @time: ptr to the given timeout value
|
|
- * @timeout: the hrtimer_sleeper structure to be set up
|
|
- * @flags: futex flags
|
|
- * @range_ns: optional range in ns
|
|
- *
|
|
- * Return: Initialized hrtimer_sleeper structure or NULL if no timeout
|
|
- * value given
|
|
- */
|
|
-static inline struct hrtimer_sleeper *
|
|
-futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
|
|
- int flags, u64 range_ns)
|
|
-{
|
|
- if (!time)
|
|
- return NULL;
|
|
-
|
|
- hrtimer_init_sleeper_on_stack(timeout, (flags & FLAGS_CLOCKRT) ?
|
|
- CLOCK_REALTIME : CLOCK_MONOTONIC,
|
|
- HRTIMER_MODE_ABS);
|
|
- /*
|
|
- * If range_ns is 0, calling hrtimer_set_expires_range_ns() is
|
|
- * effectively the same as calling hrtimer_set_expires().
|
|
- */
|
|
- hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns);
|
|
-
|
|
- return timeout;
|
|
-}
|
|
-
|
|
-/*
|
|
- * Generate a machine wide unique identifier for this inode.
|
|
- *
|
|
- * This relies on u64 not wrapping in the life-time of the machine; which with
|
|
- * 1ns resolution means almost 585 years.
|
|
- *
|
|
- * This further relies on the fact that a well formed program will not unmap
|
|
- * the file while it has a (shared) futex waiting on it. This mapping will have
|
|
- * a file reference which pins the mount and inode.
|
|
- *
|
|
- * If for some reason an inode gets evicted and read back in again, it will get
|
|
- * a new sequence number and will _NOT_ match, even though it is the exact same
|
|
- * file.
|
|
- *
|
|
- * It is important that match_futex() will never have a false-positive, esp.
|
|
- * for PI futexes that can mess up the state. The above argues that false-negatives
|
|
- * are only possible for malformed programs.
|
|
- */
|
|
-static u64 get_inode_sequence_number(struct inode *inode)
|
|
-{
|
|
- static atomic64_t i_seq;
|
|
- u64 old;
|
|
-
|
|
- /* Does the inode already have a sequence number? */
|
|
- old = atomic64_read(&inode->i_sequence);
|
|
- if (likely(old))
|
|
- return old;
|
|
-
|
|
- for (;;) {
|
|
- u64 new = atomic64_add_return(1, &i_seq);
|
|
- if (WARN_ON_ONCE(!new))
|
|
- continue;
|
|
-
|
|
- old = atomic64_cmpxchg_relaxed(&inode->i_sequence, 0, new);
|
|
- if (old)
|
|
- return old;
|
|
- return new;
|
|
- }
|
|
-}
|
|
-
|
|
-/**
|
|
- * get_futex_key() - Get parameters which are the keys for a futex
|
|
- * @uaddr: virtual address of the futex
|
|
- * @fshared: false for a PROCESS_PRIVATE futex, true for PROCESS_SHARED
|
|
- * @key: address where result is stored.
|
|
- * @rw: mapping needs to be read/write (values: FUTEX_READ,
|
|
- * FUTEX_WRITE)
|
|
- *
|
|
- * Return: a negative error code or 0
|
|
- *
|
|
- * The key words are stored in @key on success.
|
|
- *
|
|
- * For shared mappings (when @fshared), the key is:
|
|
- *
|
|
- * ( inode->i_sequence, page->index, offset_within_page )
|
|
- *
|
|
- * [ also see get_inode_sequence_number() ]
|
|
- *
|
|
- * For private mappings (or when !@fshared), the key is:
|
|
- *
|
|
- * ( current->mm, address, 0 )
|
|
- *
|
|
- * This allows (cross process, where applicable) identification of the futex
|
|
- * without keeping the page pinned for the duration of the FUTEX_WAIT.
|
|
- *
|
|
- * lock_page() might sleep, the caller should not hold a spinlock.
|
|
- */
|
|
-static int get_futex_key(u32 __user *uaddr, bool fshared, union futex_key *key,
|
|
- enum futex_access rw)
|
|
-{
|
|
- unsigned long address = (unsigned long)uaddr;
|
|
- struct mm_struct *mm = current->mm;
|
|
- struct page *page, *tail;
|
|
- struct address_space *mapping;
|
|
- int err, ro = 0;
|
|
-
|
|
- /*
|
|
- * The futex address must be "naturally" aligned.
|
|
- */
|
|
- key->both.offset = address % PAGE_SIZE;
|
|
- if (unlikely((address % sizeof(u32)) != 0))
|
|
- return -EINVAL;
|
|
- address -= key->both.offset;
|
|
-
|
|
- if (unlikely(!access_ok(uaddr, sizeof(u32))))
|
|
- return -EFAULT;
|
|
-
|
|
- if (unlikely(should_fail_futex(fshared)))
|
|
- return -EFAULT;
|
|
-
|
|
- /*
|
|
- * PROCESS_PRIVATE futexes are fast.
|
|
- * As the mm cannot disappear under us and the 'key' only needs
|
|
- * virtual address, we dont even have to find the underlying vma.
|
|
- * Note : We do have to check 'uaddr' is a valid user address,
|
|
- * but access_ok() should be faster than find_vma()
|
|
- */
|
|
- if (!fshared) {
|
|
- key->private.mm = mm;
|
|
- key->private.address = address;
|
|
- return 0;
|
|
- }
|
|
-
|
|
-again:
|
|
- /* Ignore any VERIFY_READ mapping (futex common case) */
|
|
- if (unlikely(should_fail_futex(true)))
|
|
- return -EFAULT;
|
|
-
|
|
- err = get_user_pages_fast(address, 1, FOLL_WRITE, &page);
|
|
- /*
|
|
- * If write access is not required (eg. FUTEX_WAIT), try
|
|
- * and get read-only access.
|
|
- */
|
|
- if (err == -EFAULT && rw == FUTEX_READ) {
|
|
- err = get_user_pages_fast(address, 1, 0, &page);
|
|
- ro = 1;
|
|
- }
|
|
- if (err < 0)
|
|
- return err;
|
|
- else
|
|
- err = 0;
|
|
-
|
|
- /*
|
|
- * The treatment of mapping from this point on is critical. The page
|
|
- * lock protects many things but in this context the page lock
|
|
- * stabilizes mapping, prevents inode freeing in the shared
|
|
- * file-backed region case and guards against movement to swap cache.
|
|
- *
|
|
- * Strictly speaking the page lock is not needed in all cases being
|
|
- * considered here and page lock forces unnecessarily serialization
|
|
- * From this point on, mapping will be re-verified if necessary and
|
|
- * page lock will be acquired only if it is unavoidable
|
|
- *
|
|
- * Mapping checks require the head page for any compound page so the
|
|
- * head page and mapping is looked up now. For anonymous pages, it
|
|
- * does not matter if the page splits in the future as the key is
|
|
- * based on the address. For filesystem-backed pages, the tail is
|
|
- * required as the index of the page determines the key. For
|
|
- * base pages, there is no tail page and tail == page.
|
|
- */
|
|
- tail = page;
|
|
- page = compound_head(page);
|
|
- mapping = READ_ONCE(page->mapping);
|
|
-
|
|
- /*
|
|
- * If page->mapping is NULL, then it cannot be a PageAnon
|
|
- * page; but it might be the ZERO_PAGE or in the gate area or
|
|
- * in a special mapping (all cases which we are happy to fail);
|
|
- * or it may have been a good file page when get_user_pages_fast
|
|
- * found it, but truncated or holepunched or subjected to
|
|
- * invalidate_complete_page2 before we got the page lock (also
|
|
- * cases which we are happy to fail). And we hold a reference,
|
|
- * so refcount care in invalidate_complete_page's remove_mapping
|
|
- * prevents drop_caches from setting mapping to NULL beneath us.
|
|
- *
|
|
- * The case we do have to guard against is when memory pressure made
|
|
- * shmem_writepage move it from filecache to swapcache beneath us:
|
|
- * an unlikely race, but we do need to retry for page->mapping.
|
|
- */
|
|
- if (unlikely(!mapping)) {
|
|
- int shmem_swizzled;
|
|
-
|
|
- /*
|
|
- * Page lock is required to identify which special case above
|
|
- * applies. If this is really a shmem page then the page lock
|
|
- * will prevent unexpected transitions.
|
|
- */
|
|
- lock_page(page);
|
|
- shmem_swizzled = PageSwapCache(page) || page->mapping;
|
|
- unlock_page(page);
|
|
- put_page(page);
|
|
-
|
|
- if (shmem_swizzled)
|
|
- goto again;
|
|
-
|
|
- return -EFAULT;
|
|
- }
|
|
-
|
|
- /*
|
|
- * Private mappings are handled in a simple way.
|
|
- *
|
|
- * If the futex key is stored on an anonymous page, then the associated
|
|
- * object is the mm which is implicitly pinned by the calling process.
|
|
- *
|
|
- * NOTE: When userspace waits on a MAP_SHARED mapping, even if
|
|
- * it's a read-only handle, it's expected that futexes attach to
|
|
- * the object not the particular process.
|
|
- */
|
|
- if (PageAnon(page)) {
|
|
- /*
|
|
- * A RO anonymous page will never change and thus doesn't make
|
|
- * sense for futex operations.
|
|
- */
|
|
- if (unlikely(should_fail_futex(true)) || ro) {
|
|
- err = -EFAULT;
|
|
- goto out;
|
|
- }
|
|
-
|
|
- key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
|
|
- key->private.mm = mm;
|
|
- key->private.address = address;
|
|
-
|
|
- } else {
|
|
- struct inode *inode;
|
|
-
|
|
- /*
|
|
- * The associated futex object in this case is the inode and
|
|
- * the page->mapping must be traversed. Ordinarily this should
|
|
- * be stabilised under page lock but it's not strictly
|
|
- * necessary in this case as we just want to pin the inode, not
|
|
- * update the radix tree or anything like that.
|
|
- *
|
|
- * The RCU read lock is taken as the inode is finally freed
|
|
- * under RCU. If the mapping still matches expectations then the
|
|
- * mapping->host can be safely accessed as being a valid inode.
|
|
- */
|
|
- rcu_read_lock();
|
|
-
|
|
- if (READ_ONCE(page->mapping) != mapping) {
|
|
- rcu_read_unlock();
|
|
- put_page(page);
|
|
-
|
|
- goto again;
|
|
- }
|
|
-
|
|
- inode = READ_ONCE(mapping->host);
|
|
- if (!inode) {
|
|
- rcu_read_unlock();
|
|
- put_page(page);
|
|
-
|
|
- goto again;
|
|
- }
|
|
-
|
|
- key->both.offset |= FUT_OFF_INODE; /* inode-based key */
|
|
- key->shared.i_seq = get_inode_sequence_number(inode);
|
|
- key->shared.pgoff = page_to_pgoff(tail);
|
|
- rcu_read_unlock();
|
|
- }
|
|
-
|
|
-out:
|
|
- put_page(page);
|
|
- return err;
|
|
-}
|
|
-
|
|
-/**
|
|
- * fault_in_user_writeable() - Fault in user address and verify RW access
|
|
- * @uaddr: pointer to faulting user space address
|
|
- *
|
|
- * Slow path to fixup the fault we just took in the atomic write
|
|
- * access to @uaddr.
|
|
- *
|
|
- * We have no generic implementation of a non-destructive write to the
|
|
- * user address. We know that we faulted in the atomic pagefault
|
|
- * disabled section so we can as well avoid the #PF overhead by
|
|
- * calling get_user_pages() right away.
|
|
- */
|
|
-static int fault_in_user_writeable(u32 __user *uaddr)
|
|
-{
|
|
- struct mm_struct *mm = current->mm;
|
|
- int ret;
|
|
-
|
|
- mmap_read_lock(mm);
|
|
- ret = fixup_user_fault(mm, (unsigned long)uaddr,
|
|
- FAULT_FLAG_WRITE, NULL);
|
|
- mmap_read_unlock(mm);
|
|
-
|
|
- return ret < 0 ? ret : 0;
|
|
-}
|
|
-
|
|
-/**
|
|
- * futex_top_waiter() - Return the highest priority waiter on a futex
|
|
- * @hb: the hash bucket the futex_q's reside in
|
|
- * @key: the futex key (to distinguish it from other futex futex_q's)
|
|
- *
|
|
- * Must be called with the hb lock held.
|
|
- */
|
|
-static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb,
|
|
- union futex_key *key)
|
|
-{
|
|
- struct futex_q *this;
|
|
-
|
|
- plist_for_each_entry(this, &hb->chain, list) {
|
|
- if (match_futex(&this->key, key))
|
|
- return this;
|
|
- }
|
|
- return NULL;
|
|
-}
|
|
-
|
|
-static int cmpxchg_futex_value_locked(u32 *curval, u32 __user *uaddr,
|
|
- u32 uval, u32 newval)
|
|
-{
|
|
- int ret;
|
|
-
|
|
- pagefault_disable();
|
|
- ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval);
|
|
- pagefault_enable();
|
|
-
|
|
- return ret;
|
|
-}
|
|
-
|
|
-static int get_futex_value_locked(u32 *dest, u32 __user *from)
|
|
-{
|
|
- int ret;
|
|
-
|
|
- pagefault_disable();
|
|
- ret = __get_user(*dest, from);
|
|
- pagefault_enable();
|
|
-
|
|
- return ret ? -EFAULT : 0;
|
|
-}
|
|
-
|
|
-
|
|
-/*
|
|
- * PI code:
|
|
- */
|
|
-static int refill_pi_state_cache(void)
|
|
-{
|
|
- struct futex_pi_state *pi_state;
|
|
-
|
|
- if (likely(current->pi_state_cache))
|
|
- return 0;
|
|
-
|
|
- pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
|
|
-
|
|
- if (!pi_state)
|
|
- return -ENOMEM;
|
|
-
|
|
- INIT_LIST_HEAD(&pi_state->list);
|
|
- /* pi_mutex gets initialized later */
|
|
- pi_state->owner = NULL;
|
|
- refcount_set(&pi_state->refcount, 1);
|
|
- pi_state->key = FUTEX_KEY_INIT;
|
|
-
|
|
- current->pi_state_cache = pi_state;
|
|
-
|
|
- return 0;
|
|
-}
|
|
-
|
|
-static struct futex_pi_state *alloc_pi_state(void)
|
|
-{
|
|
- struct futex_pi_state *pi_state = current->pi_state_cache;
|
|
-
|
|
- WARN_ON(!pi_state);
|
|
- current->pi_state_cache = NULL;
|
|
-
|
|
- return pi_state;
|
|
-}
|
|
-
|
|
-static void pi_state_update_owner(struct futex_pi_state *pi_state,
|
|
- struct task_struct *new_owner)
|
|
-{
|
|
- struct task_struct *old_owner = pi_state->owner;
|
|
-
|
|
- lockdep_assert_held(&pi_state->pi_mutex.wait_lock);
|
|
-
|
|
- if (old_owner) {
|
|
- raw_spin_lock(&old_owner->pi_lock);
|
|
- WARN_ON(list_empty(&pi_state->list));
|
|
- list_del_init(&pi_state->list);
|
|
- raw_spin_unlock(&old_owner->pi_lock);
|
|
- }
|
|
-
|
|
- if (new_owner) {
|
|
- raw_spin_lock(&new_owner->pi_lock);
|
|
- WARN_ON(!list_empty(&pi_state->list));
|
|
- list_add(&pi_state->list, &new_owner->pi_state_list);
|
|
- pi_state->owner = new_owner;
|
|
- raw_spin_unlock(&new_owner->pi_lock);
|
|
- }
|
|
-}
|
|
-
|
|
-static void get_pi_state(struct futex_pi_state *pi_state)
|
|
-{
|
|
- WARN_ON_ONCE(!refcount_inc_not_zero(&pi_state->refcount));
|
|
-}
|
|
-
|
|
-/*
|
|
- * Drops a reference to the pi_state object and frees or caches it
|
|
- * when the last reference is gone.
|
|
- */
|
|
-static void put_pi_state(struct futex_pi_state *pi_state)
|
|
-{
|
|
- if (!pi_state)
|
|
- return;
|
|
-
|
|
- if (!refcount_dec_and_test(&pi_state->refcount))
|
|
- return;
|
|
-
|
|
- /*
|
|
- * If pi_state->owner is NULL, the owner is most probably dying
|
|
- * and has cleaned up the pi_state already
|
|
- */
|
|
- if (pi_state->owner) {
|
|
- unsigned long flags;
|
|
-
|
|
- raw_spin_lock_irqsave(&pi_state->pi_mutex.wait_lock, flags);
|
|
- pi_state_update_owner(pi_state, NULL);
|
|
- rt_mutex_proxy_unlock(&pi_state->pi_mutex);
|
|
- raw_spin_unlock_irqrestore(&pi_state->pi_mutex.wait_lock, flags);
|
|
- }
|
|
-
|
|
- if (current->pi_state_cache) {
|
|
- kfree(pi_state);
|
|
- } else {
|
|
- /*
|
|
- * pi_state->list is already empty.
|
|
- * clear pi_state->owner.
|
|
- * refcount is at 0 - put it back to 1.
|
|
- */
|
|
- pi_state->owner = NULL;
|
|
- refcount_set(&pi_state->refcount, 1);
|
|
- current->pi_state_cache = pi_state;
|
|
- }
|
|
-}
|
|
-
|
|
-#ifdef CONFIG_FUTEX_PI
|
|
-
|
|
-/*
|
|
- * This task is holding PI mutexes at exit time => bad.
|
|
- * Kernel cleans up PI-state, but userspace is likely hosed.
|
|
- * (Robust-futex cleanup is separate and might save the day for userspace.)
|
|
- */
|
|
-static void exit_pi_state_list(struct task_struct *curr)
|
|
-{
|
|
- struct list_head *next, *head = &curr->pi_state_list;
|
|
- struct futex_pi_state *pi_state;
|
|
- struct futex_hash_bucket *hb;
|
|
- union futex_key key = FUTEX_KEY_INIT;
|
|
-
|
|
- if (!futex_cmpxchg_enabled)
|
|
- return;
|
|
- /*
|
|
- * We are a ZOMBIE and nobody can enqueue itself on
|
|
- * pi_state_list anymore, but we have to be careful
|
|
- * versus waiters unqueueing themselves:
|
|
- */
|
|
- raw_spin_lock_irq(&curr->pi_lock);
|
|
- while (!list_empty(head)) {
|
|
- next = head->next;
|
|
- pi_state = list_entry(next, struct futex_pi_state, list);
|
|
- key = pi_state->key;
|
|
- hb = hash_futex(&key);
|
|
-
|
|
- /*
|
|
- * We can race against put_pi_state() removing itself from the
|
|
- * list (a waiter going away). put_pi_state() will first
|
|
- * decrement the reference count and then modify the list, so
|
|
- * its possible to see the list entry but fail this reference
|
|
- * acquire.
|
|
- *
|
|
- * In that case; drop the locks to let put_pi_state() make
|
|
- * progress and retry the loop.
|
|
- */
|
|
- if (!refcount_inc_not_zero(&pi_state->refcount)) {
|
|
- raw_spin_unlock_irq(&curr->pi_lock);
|
|
- cpu_relax();
|
|
- raw_spin_lock_irq(&curr->pi_lock);
|
|
- continue;
|
|
- }
|
|
- raw_spin_unlock_irq(&curr->pi_lock);
|
|
-
|
|
- spin_lock(&hb->lock);
|
|
- raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
- raw_spin_lock(&curr->pi_lock);
|
|
- /*
|
|
- * We dropped the pi-lock, so re-check whether this
|
|
- * task still owns the PI-state:
|
|
- */
|
|
- if (head->next != next) {
|
|
- /* retain curr->pi_lock for the loop invariant */
|
|
- raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
|
|
- spin_unlock(&hb->lock);
|
|
- put_pi_state(pi_state);
|
|
- continue;
|
|
- }
|
|
-
|
|
- WARN_ON(pi_state->owner != curr);
|
|
- WARN_ON(list_empty(&pi_state->list));
|
|
- list_del_init(&pi_state->list);
|
|
- pi_state->owner = NULL;
|
|
-
|
|
- raw_spin_unlock(&curr->pi_lock);
|
|
- raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
- spin_unlock(&hb->lock);
|
|
-
|
|
- rt_mutex_futex_unlock(&pi_state->pi_mutex);
|
|
- put_pi_state(pi_state);
|
|
-
|
|
- raw_spin_lock_irq(&curr->pi_lock);
|
|
- }
|
|
- raw_spin_unlock_irq(&curr->pi_lock);
|
|
-}
|
|
-#else
|
|
-static inline void exit_pi_state_list(struct task_struct *curr) { }
|
|
-#endif
|
|
-
|
|
-/*
|
|
- * We need to check the following states:
|
|
- *
|
|
- * Waiter | pi_state | pi->owner | uTID | uODIED | ?
|
|
- *
|
|
- * [1] NULL | --- | --- | 0 | 0/1 | Valid
|
|
- * [2] NULL | --- | --- | >0 | 0/1 | Valid
|
|
- *
|
|
- * [3] Found | NULL | -- | Any | 0/1 | Invalid
|
|
- *
|
|
- * [4] Found | Found | NULL | 0 | 1 | Valid
|
|
- * [5] Found | Found | NULL | >0 | 1 | Invalid
|
|
- *
|
|
- * [6] Found | Found | task | 0 | 1 | Valid
|
|
- *
|
|
- * [7] Found | Found | NULL | Any | 0 | Invalid
|
|
- *
|
|
- * [8] Found | Found | task | ==taskTID | 0/1 | Valid
|
|
- * [9] Found | Found | task | 0 | 0 | Invalid
|
|
- * [10] Found | Found | task | !=taskTID | 0/1 | Invalid
|
|
- *
|
|
- * [1] Indicates that the kernel can acquire the futex atomically. We
|
|
- * came here due to a stale FUTEX_WAITERS/FUTEX_OWNER_DIED bit.
|
|
- *
|
|
- * [2] Valid, if TID does not belong to a kernel thread. If no matching
|
|
- * thread is found then it indicates that the owner TID has died.
|
|
- *
|
|
- * [3] Invalid. The waiter is queued on a non PI futex
|
|
- *
|
|
- * [4] Valid state after exit_robust_list(), which sets the user space
|
|
- * value to FUTEX_WAITERS | FUTEX_OWNER_DIED.
|
|
- *
|
|
- * [5] The user space value got manipulated between exit_robust_list()
|
|
- * and exit_pi_state_list()
|
|
- *
|
|
- * [6] Valid state after exit_pi_state_list() which sets the new owner in
|
|
- * the pi_state but cannot access the user space value.
|
|
- *
|
|
- * [7] pi_state->owner can only be NULL when the OWNER_DIED bit is set.
|
|
- *
|
|
- * [8] Owner and user space value match
|
|
- *
|
|
- * [9] There is no transient state which sets the user space TID to 0
|
|
- * except exit_robust_list(), but this is indicated by the
|
|
- * FUTEX_OWNER_DIED bit. See [4]
|
|
- *
|
|
- * [10] There is no transient state which leaves owner and user space
|
|
- * TID out of sync. Except one error case where the kernel is denied
|
|
- * write access to the user address, see fixup_pi_state_owner().
|
|
- *
|
|
- *
|
|
- * Serialization and lifetime rules:
|
|
- *
|
|
- * hb->lock:
|
|
- *
|
|
- * hb -> futex_q, relation
|
|
- * futex_q -> pi_state, relation
|
|
- *
|
|
- * (cannot be raw because hb can contain arbitrary amount
|
|
- * of futex_q's)
|
|
- *
|
|
- * pi_mutex->wait_lock:
|
|
- *
|
|
- * {uval, pi_state}
|
|
- *
|
|
- * (and pi_mutex 'obviously')
|
|
- *
|
|
- * p->pi_lock:
|
|
- *
|
|
- * p->pi_state_list -> pi_state->list, relation
|
|
- * pi_mutex->owner -> pi_state->owner, relation
|
|
- *
|
|
- * pi_state->refcount:
|
|
- *
|
|
- * pi_state lifetime
|
|
- *
|
|
- *
|
|
- * Lock order:
|
|
- *
|
|
- * hb->lock
|
|
- * pi_mutex->wait_lock
|
|
- * p->pi_lock
|
|
- *
|
|
- */
|
|
-
|
|
-/*
|
|
- * Validate that the existing waiter has a pi_state and sanity check
|
|
- * the pi_state against the user space value. If correct, attach to
|
|
- * it.
|
|
- */
|
|
-static int attach_to_pi_state(u32 __user *uaddr, u32 uval,
|
|
- struct futex_pi_state *pi_state,
|
|
- struct futex_pi_state **ps)
|
|
-{
|
|
- pid_t pid = uval & FUTEX_TID_MASK;
|
|
- u32 uval2;
|
|
- int ret;
|
|
-
|
|
- /*
|
|
- * Userspace might have messed up non-PI and PI futexes [3]
|
|
- */
|
|
- if (unlikely(!pi_state))
|
|
- return -EINVAL;
|
|
-
|
|
- /*
|
|
- * We get here with hb->lock held, and having found a
|
|
- * futex_top_waiter(). This means that futex_lock_pi() of said futex_q
|
|
- * has dropped the hb->lock in between queue_me() and unqueue_me_pi(),
|
|
- * which in turn means that futex_lock_pi() still has a reference on
|
|
- * our pi_state.
|
|
- *
|
|
- * The waiter holding a reference on @pi_state also protects against
|
|
- * the unlocked put_pi_state() in futex_unlock_pi(), futex_lock_pi()
|
|
- * and futex_wait_requeue_pi() as it cannot go to 0 and consequently
|
|
- * free pi_state before we can take a reference ourselves.
|
|
- */
|
|
- WARN_ON(!refcount_read(&pi_state->refcount));
|
|
-
|
|
- /*
|
|
- * Now that we have a pi_state, we can acquire wait_lock
|
|
- * and do the state validation.
|
|
- */
|
|
- raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
-
|
|
- /*
|
|
- * Since {uval, pi_state} is serialized by wait_lock, and our current
|
|
- * uval was read without holding it, it can have changed. Verify it
|
|
- * still is what we expect it to be, otherwise retry the entire
|
|
- * operation.
|
|
- */
|
|
- if (get_futex_value_locked(&uval2, uaddr))
|
|
- goto out_efault;
|
|
-
|
|
- if (uval != uval2)
|
|
- goto out_eagain;
|
|
-
|
|
- /*
|
|
- * Handle the owner died case:
|
|
- */
|
|
- if (uval & FUTEX_OWNER_DIED) {
|
|
- /*
|
|
- * exit_pi_state_list sets owner to NULL and wakes the
|
|
- * topmost waiter. The task which acquires the
|
|
- * pi_state->rt_mutex will fixup owner.
|
|
- */
|
|
- if (!pi_state->owner) {
|
|
- /*
|
|
- * No pi state owner, but the user space TID
|
|
- * is not 0. Inconsistent state. [5]
|
|
- */
|
|
- if (pid)
|
|
- goto out_einval;
|
|
- /*
|
|
- * Take a ref on the state and return success. [4]
|
|
- */
|
|
- goto out_attach;
|
|
- }
|
|
-
|
|
- /*
|
|
- * If TID is 0, then either the dying owner has not
|
|
- * yet executed exit_pi_state_list() or some waiter
|
|
- * acquired the rtmutex in the pi state, but did not
|
|
- * yet fixup the TID in user space.
|
|
- *
|
|
- * Take a ref on the state and return success. [6]
|
|
- */
|
|
- if (!pid)
|
|
- goto out_attach;
|
|
- } else {
|
|
- /*
|
|
- * If the owner died bit is not set, then the pi_state
|
|
- * must have an owner. [7]
|
|
- */
|
|
- if (!pi_state->owner)
|
|
- goto out_einval;
|
|
- }
|
|
-
|
|
- /*
|
|
- * Bail out if user space manipulated the futex value. If pi
|
|
- * state exists then the owner TID must be the same as the
|
|
- * user space TID. [9/10]
|
|
- */
|
|
- if (pid != task_pid_vnr(pi_state->owner))
|
|
- goto out_einval;
|
|
-
|
|
-out_attach:
|
|
- get_pi_state(pi_state);
|
|
- raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
- *ps = pi_state;
|
|
- return 0;
|
|
-
|
|
-out_einval:
|
|
- ret = -EINVAL;
|
|
- goto out_error;
|
|
-
|
|
-out_eagain:
|
|
- ret = -EAGAIN;
|
|
- goto out_error;
|
|
-
|
|
-out_efault:
|
|
- ret = -EFAULT;
|
|
- goto out_error;
|
|
-
|
|
-out_error:
|
|
- raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
- return ret;
|
|
-}
|
|
-
|
|
-/**
|
|
- * wait_for_owner_exiting - Block until the owner has exited
|
|
- * @ret: owner's current futex lock status
|
|
- * @exiting: Pointer to the exiting task
|
|
- *
|
|
- * Caller must hold a refcount on @exiting.
|
|
- */
|
|
-static void wait_for_owner_exiting(int ret, struct task_struct *exiting)
|
|
-{
|
|
- if (ret != -EBUSY) {
|
|
- WARN_ON_ONCE(exiting);
|
|
- return;
|
|
- }
|
|
-
|
|
- if (WARN_ON_ONCE(ret == -EBUSY && !exiting))
|
|
- return;
|
|
-
|
|
- mutex_lock(&exiting->futex_exit_mutex);
|
|
- /*
|
|
- * No point in doing state checking here. If the waiter got here
|
|
- * while the task was in exec()->exec_futex_release() then it can
|
|
- * have any FUTEX_STATE_* value when the waiter has acquired the
|
|
- * mutex. OK, if running, EXITING or DEAD if it reached exit()
|
|
- * already. Highly unlikely and not a problem. Just one more round
|
|
- * through the futex maze.
|
|
- */
|
|
- mutex_unlock(&exiting->futex_exit_mutex);
|
|
-
|
|
- put_task_struct(exiting);
|
|
-}
|
|
-
|
|
-static int handle_exit_race(u32 __user *uaddr, u32 uval,
|
|
- struct task_struct *tsk)
|
|
-{
|
|
- u32 uval2;
|
|
-
|
|
- /*
|
|
- * If the futex exit state is not yet FUTEX_STATE_DEAD, tell the
|
|
- * caller that the alleged owner is busy.
|
|
- */
|
|
- if (tsk && tsk->futex_state != FUTEX_STATE_DEAD)
|
|
- return -EBUSY;
|
|
-
|
|
- /*
|
|
- * Reread the user space value to handle the following situation:
|
|
- *
|
|
- * CPU0 CPU1
|
|
- *
|
|
- * sys_exit() sys_futex()
|
|
- * do_exit() futex_lock_pi()
|
|
- * futex_lock_pi_atomic()
|
|
- * exit_signals(tsk) No waiters:
|
|
- * tsk->flags |= PF_EXITING; *uaddr == 0x00000PID
|
|
- * mm_release(tsk) Set waiter bit
|
|
- * exit_robust_list(tsk) { *uaddr = 0x80000PID;
|
|
- * Set owner died attach_to_pi_owner() {
|
|
- * *uaddr = 0xC0000000; tsk = get_task(PID);
|
|
- * } if (!tsk->flags & PF_EXITING) {
|
|
- * ... attach();
|
|
- * tsk->futex_state = } else {
|
|
- * FUTEX_STATE_DEAD; if (tsk->futex_state !=
|
|
- * FUTEX_STATE_DEAD)
|
|
- * return -EAGAIN;
|
|
- * return -ESRCH; <--- FAIL
|
|
- * }
|
|
- *
|
|
- * Returning ESRCH unconditionally is wrong here because the
|
|
- * user space value has been changed by the exiting task.
|
|
- *
|
|
- * The same logic applies to the case where the exiting task is
|
|
- * already gone.
|
|
- */
|
|
- if (get_futex_value_locked(&uval2, uaddr))
|
|
- return -EFAULT;
|
|
-
|
|
- /* If the user space value has changed, try again. */
|
|
- if (uval2 != uval)
|
|
- return -EAGAIN;
|
|
-
|
|
- /*
|
|
- * The exiting task did not have a robust list, the robust list was
|
|
- * corrupted or the user space value in *uaddr is simply bogus.
|
|
- * Give up and tell user space.
|
|
- */
|
|
- return -ESRCH;
|
|
-}
|
|
-
|
|
-static void __attach_to_pi_owner(struct task_struct *p, union futex_key *key,
|
|
- struct futex_pi_state **ps)
|
|
-{
|
|
- /*
|
|
- * No existing pi state. First waiter. [2]
|
|
- *
|
|
- * This creates pi_state, we have hb->lock held, this means nothing can
|
|
- * observe this state, wait_lock is irrelevant.
|
|
- */
|
|
- struct futex_pi_state *pi_state = alloc_pi_state();
|
|
-
|
|
- /*
|
|
- * Initialize the pi_mutex in locked state and make @p
|
|
- * the owner of it:
|
|
- */
|
|
- rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
|
|
-
|
|
- /* Store the key for possible exit cleanups: */
|
|
- pi_state->key = *key;
|
|
-
|
|
- WARN_ON(!list_empty(&pi_state->list));
|
|
- list_add(&pi_state->list, &p->pi_state_list);
|
|
- /*
|
|
- * Assignment without holding pi_state->pi_mutex.wait_lock is safe
|
|
- * because there is no concurrency as the object is not published yet.
|
|
- */
|
|
- pi_state->owner = p;
|
|
-
|
|
- *ps = pi_state;
|
|
-}
|
|
-/*
|
|
- * Lookup the task for the TID provided from user space and attach to
|
|
- * it after doing proper sanity checks.
|
|
- */
|
|
-static int attach_to_pi_owner(u32 __user *uaddr, u32 uval, union futex_key *key,
|
|
- struct futex_pi_state **ps,
|
|
- struct task_struct **exiting)
|
|
-{
|
|
- pid_t pid = uval & FUTEX_TID_MASK;
|
|
- struct task_struct *p;
|
|
-
|
|
- /*
|
|
- * We are the first waiter - try to look up the real owner and attach
|
|
- * the new pi_state to it, but bail out when TID = 0 [1]
|
|
- *
|
|
- * The !pid check is paranoid. None of the call sites should end up
|
|
- * with pid == 0, but better safe than sorry. Let the caller retry
|
|
- */
|
|
- if (!pid)
|
|
- return -EAGAIN;
|
|
- p = find_get_task_by_vpid(pid);
|
|
- if (!p)
|
|
- return handle_exit_race(uaddr, uval, NULL);
|
|
-
|
|
- if (unlikely(p->flags & PF_KTHREAD)) {
|
|
- put_task_struct(p);
|
|
- return -EPERM;
|
|
- }
|
|
-
|
|
- /*
|
|
- * We need to look at the task state to figure out, whether the
|
|
- * task is exiting. To protect against the change of the task state
|
|
- * in futex_exit_release(), we do this protected by p->pi_lock:
|
|
- */
|
|
- raw_spin_lock_irq(&p->pi_lock);
|
|
- if (unlikely(p->futex_state != FUTEX_STATE_OK)) {
|
|
- /*
|
|
- * The task is on the way out. When the futex state is
|
|
- * FUTEX_STATE_DEAD, we know that the task has finished
|
|
- * the cleanup:
|
|
- */
|
|
- int ret = handle_exit_race(uaddr, uval, p);
|
|
-
|
|
- raw_spin_unlock_irq(&p->pi_lock);
|
|
- /*
|
|
- * If the owner task is between FUTEX_STATE_EXITING and
|
|
- * FUTEX_STATE_DEAD then store the task pointer and keep
|
|
- * the reference on the task struct. The calling code will
|
|
- * drop all locks, wait for the task to reach
|
|
- * FUTEX_STATE_DEAD and then drop the refcount. This is
|
|
- * required to prevent a live lock when the current task
|
|
- * preempted the exiting task between the two states.
|
|
- */
|
|
- if (ret == -EBUSY)
|
|
- *exiting = p;
|
|
- else
|
|
- put_task_struct(p);
|
|
- return ret;
|
|
- }
|
|
-
|
|
- __attach_to_pi_owner(p, key, ps);
|
|
- raw_spin_unlock_irq(&p->pi_lock);
|
|
-
|
|
- put_task_struct(p);
|
|
-
|
|
- return 0;
|
|
-}
|
|
-
|
|
-static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval)
|
|
-{
|
|
- int err;
|
|
- u32 curval;
|
|
-
|
|
- if (unlikely(should_fail_futex(true)))
|
|
- return -EFAULT;
|
|
-
|
|
- err = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
|
|
- if (unlikely(err))
|
|
- return err;
|
|
-
|
|
- /* If user space value changed, let the caller retry */
|
|
- return curval != uval ? -EAGAIN : 0;
|
|
-}
|
|
-
|
|
-/**
|
|
- * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex
|
|
- * @uaddr: the pi futex user address
|
|
- * @hb: the pi futex hash bucket
|
|
- * @key: the futex key associated with uaddr and hb
|
|
- * @ps: the pi_state pointer where we store the result of the
|
|
- * lookup
|
|
- * @task: the task to perform the atomic lock work for. This will
|
|
- * be "current" except in the case of requeue pi.
|
|
- * @exiting: Pointer to store the task pointer of the owner task
|
|
- * which is in the middle of exiting
|
|
- * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
|
|
- *
|
|
- * Return:
|
|
- * - 0 - ready to wait;
|
|
- * - 1 - acquired the lock;
|
|
- * - <0 - error
|
|
- *
|
|
- * The hb->lock must be held by the caller.
|
|
- *
|
|
- * @exiting is only set when the return value is -EBUSY. If so, this holds
|
|
- * a refcount on the exiting task on return and the caller needs to drop it
|
|
- * after waiting for the exit to complete.
|
|
- */
|
|
-static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
|
|
- union futex_key *key,
|
|
- struct futex_pi_state **ps,
|
|
- struct task_struct *task,
|
|
- struct task_struct **exiting,
|
|
- int set_waiters)
|
|
-{
|
|
- u32 uval, newval, vpid = task_pid_vnr(task);
|
|
- struct futex_q *top_waiter;
|
|
- int ret;
|
|
-
|
|
- /*
|
|
- * Read the user space value first so we can validate a few
|
|
- * things before proceeding further.
|
|
- */
|
|
- if (get_futex_value_locked(&uval, uaddr))
|
|
- return -EFAULT;
|
|
-
|
|
- if (unlikely(should_fail_futex(true)))
|
|
- return -EFAULT;
|
|
-
|
|
- /*
|
|
- * Detect deadlocks.
|
|
- */
|
|
- if ((unlikely((uval & FUTEX_TID_MASK) == vpid)))
|
|
- return -EDEADLK;
|
|
-
|
|
- if ((unlikely(should_fail_futex(true))))
|
|
- return -EDEADLK;
|
|
-
|
|
- /*
|
|
- * Lookup existing state first. If it exists, try to attach to
|
|
- * its pi_state.
|
|
- */
|
|
- top_waiter = futex_top_waiter(hb, key);
|
|
- if (top_waiter)
|
|
- return attach_to_pi_state(uaddr, uval, top_waiter->pi_state, ps);
|
|
-
|
|
- /*
|
|
- * No waiter and user TID is 0. We are here because the
|
|
- * waiters or the owner died bit is set or called from
|
|
- * requeue_cmp_pi or for whatever reason something took the
|
|
- * syscall.
|
|
- */
|
|
- if (!(uval & FUTEX_TID_MASK)) {
|
|
- /*
|
|
- * We take over the futex. No other waiters and the user space
|
|
- * TID is 0. We preserve the owner died bit.
|
|
- */
|
|
- newval = uval & FUTEX_OWNER_DIED;
|
|
- newval |= vpid;
|
|
-
|
|
- /* The futex requeue_pi code can enforce the waiters bit */
|
|
- if (set_waiters)
|
|
- newval |= FUTEX_WAITERS;
|
|
-
|
|
- ret = lock_pi_update_atomic(uaddr, uval, newval);
|
|
- if (ret)
|
|
- return ret;
|
|
-
|
|
- /*
|
|
- * If the waiter bit was requested the caller also needs PI
|
|
- * state attached to the new owner of the user space futex.
|
|
- *
|
|
- * @task is guaranteed to be alive and it cannot be exiting
|
|
- * because it is either sleeping or waiting in
|
|
- * futex_requeue_pi_wakeup_sync().
|
|
- *
|
|
- * No need to do the full attach_to_pi_owner() exercise
|
|
- * because @task is known and valid.
|
|
- */
|
|
- if (set_waiters) {
|
|
- raw_spin_lock_irq(&task->pi_lock);
|
|
- __attach_to_pi_owner(task, key, ps);
|
|
- raw_spin_unlock_irq(&task->pi_lock);
|
|
- }
|
|
- return 1;
|
|
- }
|
|
-
|
|
- /*
|
|
- * First waiter. Set the waiters bit before attaching ourself to
|
|
- * the owner. If owner tries to unlock, it will be forced into
|
|
- * the kernel and blocked on hb->lock.
|
|
- */
|
|
- newval = uval | FUTEX_WAITERS;
|
|
- ret = lock_pi_update_atomic(uaddr, uval, newval);
|
|
- if (ret)
|
|
- return ret;
|
|
- /*
|
|
- * If the update of the user space value succeeded, we try to
|
|
- * attach to the owner. If that fails, no harm done, we only
|
|
- * set the FUTEX_WAITERS bit in the user space variable.
|
|
- */
|
|
- return attach_to_pi_owner(uaddr, newval, key, ps, exiting);
|
|
-}
|
|
-
|
|
-/**
|
|
- * __unqueue_futex() - Remove the futex_q from its futex_hash_bucket
|
|
- * @q: The futex_q to unqueue
|
|
- *
|
|
- * The q->lock_ptr must not be NULL and must be held by the caller.
|
|
- */
|
|
-static void __unqueue_futex(struct futex_q *q)
|
|
-{
|
|
- struct futex_hash_bucket *hb;
|
|
-
|
|
- if (WARN_ON_SMP(!q->lock_ptr) || WARN_ON(plist_node_empty(&q->list)))
|
|
- return;
|
|
- lockdep_assert_held(q->lock_ptr);
|
|
-
|
|
- hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock);
|
|
- plist_del(&q->list, &hb->chain);
|
|
- hb_waiters_dec(hb);
|
|
-}
|
|
-
|
|
-/*
|
|
- * The hash bucket lock must be held when this is called.
|
|
- * Afterwards, the futex_q must not be accessed. Callers
|
|
- * must ensure to later call wake_up_q() for the actual
|
|
- * wakeups to occur.
|
|
- */
|
|
-static void mark_wake_futex(struct wake_q_head *wake_q, struct futex_q *q)
|
|
-{
|
|
- struct task_struct *p = q->task;
|
|
-
|
|
- if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n"))
|
|
- return;
|
|
-
|
|
- get_task_struct(p);
|
|
- __unqueue_futex(q);
|
|
- /*
|
|
- * The waiting task can free the futex_q as soon as q->lock_ptr = NULL
|
|
- * is written, without taking any locks. This is possible in the event
|
|
- * of a spurious wakeup, for example. A memory barrier is required here
|
|
- * to prevent the following store to lock_ptr from getting ahead of the
|
|
- * plist_del in __unqueue_futex().
|
|
- */
|
|
- smp_store_release(&q->lock_ptr, NULL);
|
|
-
|
|
- /*
|
|
- * Queue the task for later wakeup for after we've released
|
|
- * the hb->lock.
|
|
- */
|
|
- wake_q_add_safe(wake_q, p);
|
|
-}
|
|
-
|
|
-/*
|
|
- * Caller must hold a reference on @pi_state.
|
|
- */
|
|
-static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_state)
|
|
-{
|
|
- struct rt_mutex_waiter *top_waiter;
|
|
- struct task_struct *new_owner;
|
|
- bool postunlock = false;
|
|
- DEFINE_RT_WAKE_Q(wqh);
|
|
- u32 curval, newval;
|
|
- int ret = 0;
|
|
-
|
|
- top_waiter = rt_mutex_top_waiter(&pi_state->pi_mutex);
|
|
- if (WARN_ON_ONCE(!top_waiter)) {
|
|
- /*
|
|
- * As per the comment in futex_unlock_pi() this should not happen.
|
|
- *
|
|
- * When this happens, give up our locks and try again, giving
|
|
- * the futex_lock_pi() instance time to complete, either by
|
|
- * waiting on the rtmutex or removing itself from the futex
|
|
- * queue.
|
|
- */
|
|
- ret = -EAGAIN;
|
|
- goto out_unlock;
|
|
- }
|
|
-
|
|
- new_owner = top_waiter->task;
|
|
-
|
|
- /*
|
|
- * We pass it to the next owner. The WAITERS bit is always kept
|
|
- * enabled while there is PI state around. We cleanup the owner
|
|
- * died bit, because we are the owner.
|
|
- */
|
|
- newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
|
|
-
|
|
- if (unlikely(should_fail_futex(true))) {
|
|
- ret = -EFAULT;
|
|
- goto out_unlock;
|
|
- }
|
|
-
|
|
- ret = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
|
|
- if (!ret && (curval != uval)) {
|
|
- /*
|
|
- * If a unconditional UNLOCK_PI operation (user space did not
|
|
- * try the TID->0 transition) raced with a waiter setting the
|
|
- * FUTEX_WAITERS flag between get_user() and locking the hash
|
|
- * bucket lock, retry the operation.
|
|
- */
|
|
- if ((FUTEX_TID_MASK & curval) == uval)
|
|
- ret = -EAGAIN;
|
|
- else
|
|
- ret = -EINVAL;
|
|
- }
|
|
-
|
|
- if (!ret) {
|
|
- /*
|
|
- * This is a point of no return; once we modified the uval
|
|
- * there is no going back and subsequent operations must
|
|
- * not fail.
|
|
- */
|
|
- pi_state_update_owner(pi_state, new_owner);
|
|
- postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wqh);
|
|
- }
|
|
-
|
|
-out_unlock:
|
|
- raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
-
|
|
- if (postunlock)
|
|
- rt_mutex_postunlock(&wqh);
|
|
-
|
|
- return ret;
|
|
-}
|
|
-
|
|
-/*
|
|
- * Express the locking dependencies for lockdep:
|
|
- */
|
|
-static inline void
|
|
-double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
|
|
-{
|
|
- if (hb1 <= hb2) {
|
|
- spin_lock(&hb1->lock);
|
|
- if (hb1 < hb2)
|
|
- spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
|
|
- } else { /* hb1 > hb2 */
|
|
- spin_lock(&hb2->lock);
|
|
- spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
|
|
- }
|
|
-}
|
|
-
|
|
-static inline void
|
|
-double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
|
|
-{
|
|
- spin_unlock(&hb1->lock);
|
|
- if (hb1 != hb2)
|
|
- spin_unlock(&hb2->lock);
|
|
-}
|
|
-
|
|
-/*
|
|
- * Wake up waiters matching bitset queued on this futex (uaddr).
|
|
- */
|
|
-static int
|
|
-futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
|
|
-{
|
|
- struct futex_hash_bucket *hb;
|
|
- struct futex_q *this, *next;
|
|
- union futex_key key = FUTEX_KEY_INIT;
|
|
- int ret;
|
|
- DEFINE_WAKE_Q(wake_q);
|
|
-
|
|
- if (!bitset)
|
|
- return -EINVAL;
|
|
-
|
|
- ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, FUTEX_READ);
|
|
- if (unlikely(ret != 0))
|
|
- return ret;
|
|
-
|
|
- hb = hash_futex(&key);
|
|
-
|
|
- /* Make sure we really have tasks to wakeup */
|
|
- if (!hb_waiters_pending(hb))
|
|
- return ret;
|
|
-
|
|
- spin_lock(&hb->lock);
|
|
-
|
|
- plist_for_each_entry_safe(this, next, &hb->chain, list) {
|
|
- if (match_futex (&this->key, &key)) {
|
|
- if (this->pi_state || this->rt_waiter) {
|
|
- ret = -EINVAL;
|
|
- break;
|
|
- }
|
|
-
|
|
- /* Check if one of the bits is set in both bitsets */
|
|
- if (!(this->bitset & bitset))
|
|
- continue;
|
|
-
|
|
- mark_wake_futex(&wake_q, this);
|
|
- if (++ret >= nr_wake)
|
|
- break;
|
|
- }
|
|
- }
|
|
-
|
|
- spin_unlock(&hb->lock);
|
|
- wake_up_q(&wake_q);
|
|
- return ret;
|
|
-}
|
|
-
|
|
-static int futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr)
|
|
-{
|
|
- unsigned int op = (encoded_op & 0x70000000) >> 28;
|
|
- unsigned int cmp = (encoded_op & 0x0f000000) >> 24;
|
|
- int oparg = sign_extend32((encoded_op & 0x00fff000) >> 12, 11);
|
|
- int cmparg = sign_extend32(encoded_op & 0x00000fff, 11);
|
|
- int oldval, ret;
|
|
-
|
|
- if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) {
|
|
- if (oparg < 0 || oparg > 31) {
|
|
- char comm[sizeof(current->comm)];
|
|
- /*
|
|
- * kill this print and return -EINVAL when userspace
|
|
- * is sane again
|
|
- */
|
|
- pr_info_ratelimited("futex_wake_op: %s tries to shift op by %d; fix this program\n",
|
|
- get_task_comm(comm, current), oparg);
|
|
- oparg &= 31;
|
|
- }
|
|
- oparg = 1 << oparg;
|
|
- }
|
|
-
|
|
- pagefault_disable();
|
|
- ret = arch_futex_atomic_op_inuser(op, oparg, &oldval, uaddr);
|
|
- pagefault_enable();
|
|
- if (ret)
|
|
- return ret;
|
|
-
|
|
- switch (cmp) {
|
|
- case FUTEX_OP_CMP_EQ:
|
|
- return oldval == cmparg;
|
|
- case FUTEX_OP_CMP_NE:
|
|
- return oldval != cmparg;
|
|
- case FUTEX_OP_CMP_LT:
|
|
- return oldval < cmparg;
|
|
- case FUTEX_OP_CMP_GE:
|
|
- return oldval >= cmparg;
|
|
- case FUTEX_OP_CMP_LE:
|
|
- return oldval <= cmparg;
|
|
- case FUTEX_OP_CMP_GT:
|
|
- return oldval > cmparg;
|
|
- default:
|
|
- return -ENOSYS;
|
|
- }
|
|
-}
|
|
-
|
|
-/*
|
|
- * Wake up all waiters hashed on the physical page that is mapped
|
|
- * to this virtual address:
|
|
- */
|
|
-static int
|
|
-futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2,
|
|
- int nr_wake, int nr_wake2, int op)
|
|
-{
|
|
- union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
|
|
- struct futex_hash_bucket *hb1, *hb2;
|
|
- struct futex_q *this, *next;
|
|
- int ret, op_ret;
|
|
- DEFINE_WAKE_Q(wake_q);
|
|
-
|
|
-retry:
|
|
- ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, FUTEX_READ);
|
|
- if (unlikely(ret != 0))
|
|
- return ret;
|
|
- ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, FUTEX_WRITE);
|
|
- if (unlikely(ret != 0))
|
|
- return ret;
|
|
-
|
|
- hb1 = hash_futex(&key1);
|
|
- hb2 = hash_futex(&key2);
|
|
-
|
|
-retry_private:
|
|
- double_lock_hb(hb1, hb2);
|
|
- op_ret = futex_atomic_op_inuser(op, uaddr2);
|
|
- if (unlikely(op_ret < 0)) {
|
|
- double_unlock_hb(hb1, hb2);
|
|
-
|
|
- if (!IS_ENABLED(CONFIG_MMU) ||
|
|
- unlikely(op_ret != -EFAULT && op_ret != -EAGAIN)) {
|
|
- /*
|
|
- * we don't get EFAULT from MMU faults if we don't have
|
|
- * an MMU, but we might get them from range checking
|
|
- */
|
|
- ret = op_ret;
|
|
- return ret;
|
|
- }
|
|
-
|
|
- if (op_ret == -EFAULT) {
|
|
- ret = fault_in_user_writeable(uaddr2);
|
|
- if (ret)
|
|
- return ret;
|
|
- }
|
|
-
|
|
- cond_resched();
|
|
- if (!(flags & FLAGS_SHARED))
|
|
- goto retry_private;
|
|
- goto retry;
|
|
- }
|
|
-
|
|
- plist_for_each_entry_safe(this, next, &hb1->chain, list) {
|
|
- if (match_futex (&this->key, &key1)) {
|
|
- if (this->pi_state || this->rt_waiter) {
|
|
- ret = -EINVAL;
|
|
- goto out_unlock;
|
|
- }
|
|
- mark_wake_futex(&wake_q, this);
|
|
- if (++ret >= nr_wake)
|
|
- break;
|
|
- }
|
|
- }
|
|
-
|
|
- if (op_ret > 0) {
|
|
- op_ret = 0;
|
|
- plist_for_each_entry_safe(this, next, &hb2->chain, list) {
|
|
- if (match_futex (&this->key, &key2)) {
|
|
- if (this->pi_state || this->rt_waiter) {
|
|
- ret = -EINVAL;
|
|
- goto out_unlock;
|
|
- }
|
|
- mark_wake_futex(&wake_q, this);
|
|
- if (++op_ret >= nr_wake2)
|
|
- break;
|
|
- }
|
|
- }
|
|
- ret += op_ret;
|
|
- }
|
|
-
|
|
-out_unlock:
|
|
- double_unlock_hb(hb1, hb2);
|
|
- wake_up_q(&wake_q);
|
|
- return ret;
|
|
-}
|
|
-
|
|
-/**
|
|
- * requeue_futex() - Requeue a futex_q from one hb to another
|
|
- * @q: the futex_q to requeue
|
|
- * @hb1: the source hash_bucket
|
|
- * @hb2: the target hash_bucket
|
|
- * @key2: the new key for the requeued futex_q
|
|
- */
|
|
-static inline
|
|
-void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1,
|
|
- struct futex_hash_bucket *hb2, union futex_key *key2)
|
|
-{
|
|
-
|
|
- /*
|
|
- * If key1 and key2 hash to the same bucket, no need to
|
|
- * requeue.
|
|
- */
|
|
- if (likely(&hb1->chain != &hb2->chain)) {
|
|
- plist_del(&q->list, &hb1->chain);
|
|
- hb_waiters_dec(hb1);
|
|
- hb_waiters_inc(hb2);
|
|
- plist_add(&q->list, &hb2->chain);
|
|
- q->lock_ptr = &hb2->lock;
|
|
- }
|
|
- q->key = *key2;
|
|
-}
|
|
-
|
|
-static inline bool futex_requeue_pi_prepare(struct futex_q *q,
|
|
- struct futex_pi_state *pi_state)
|
|
-{
|
|
- int old, new;
|
|
-
|
|
- /*
|
|
- * Set state to Q_REQUEUE_PI_IN_PROGRESS unless an early wakeup has
|
|
- * already set Q_REQUEUE_PI_IGNORE to signal that requeue should
|
|
- * ignore the waiter.
|
|
- */
|
|
- old = atomic_read_acquire(&q->requeue_state);
|
|
- do {
|
|
- if (old == Q_REQUEUE_PI_IGNORE)
|
|
- return false;
|
|
-
|
|
- /*
|
|
- * futex_proxy_trylock_atomic() might have set it to
|
|
- * IN_PROGRESS and a interleaved early wake to WAIT.
|
|
- *
|
|
- * It was considered to have an extra state for that
|
|
- * trylock, but that would just add more conditionals
|
|
- * all over the place for a dubious value.
|
|
- */
|
|
- if (old != Q_REQUEUE_PI_NONE)
|
|
- break;
|
|
-
|
|
- new = Q_REQUEUE_PI_IN_PROGRESS;
|
|
- } while (!atomic_try_cmpxchg(&q->requeue_state, &old, new));
|
|
-
|
|
- q->pi_state = pi_state;
|
|
- return true;
|
|
-}
|
|
-
|
|
-static inline void futex_requeue_pi_complete(struct futex_q *q, int locked)
|
|
-{
|
|
- int old, new;
|
|
-
|
|
- old = atomic_read_acquire(&q->requeue_state);
|
|
- do {
|
|
- if (old == Q_REQUEUE_PI_IGNORE)
|
|
- return;
|
|
-
|
|
- if (locked >= 0) {
|
|
- /* Requeue succeeded. Set DONE or LOCKED */
|
|
- WARN_ON_ONCE(old != Q_REQUEUE_PI_IN_PROGRESS &&
|
|
- old != Q_REQUEUE_PI_WAIT);
|
|
- new = Q_REQUEUE_PI_DONE + locked;
|
|
- } else if (old == Q_REQUEUE_PI_IN_PROGRESS) {
|
|
- /* Deadlock, no early wakeup interleave */
|
|
- new = Q_REQUEUE_PI_NONE;
|
|
- } else {
|
|
- /* Deadlock, early wakeup interleave. */
|
|
- WARN_ON_ONCE(old != Q_REQUEUE_PI_WAIT);
|
|
- new = Q_REQUEUE_PI_IGNORE;
|
|
- }
|
|
- } while (!atomic_try_cmpxchg(&q->requeue_state, &old, new));
|
|
-
|
|
-#ifdef CONFIG_PREEMPT_RT
|
|
- /* If the waiter interleaved with the requeue let it know */
|
|
- if (unlikely(old == Q_REQUEUE_PI_WAIT))
|
|
- rcuwait_wake_up(&q->requeue_wait);
|
|
-#endif
|
|
-}
|
|
-
|
|
-static inline int futex_requeue_pi_wakeup_sync(struct futex_q *q)
|
|
-{
|
|
- int old, new;
|
|
-
|
|
- old = atomic_read_acquire(&q->requeue_state);
|
|
- do {
|
|
- /* Is requeue done already? */
|
|
- if (old >= Q_REQUEUE_PI_DONE)
|
|
- return old;
|
|
-
|
|
- /*
|
|
- * If not done, then tell the requeue code to either ignore
|
|
- * the waiter or to wake it up once the requeue is done.
|
|
- */
|
|
- new = Q_REQUEUE_PI_WAIT;
|
|
- if (old == Q_REQUEUE_PI_NONE)
|
|
- new = Q_REQUEUE_PI_IGNORE;
|
|
- } while (!atomic_try_cmpxchg(&q->requeue_state, &old, new));
|
|
-
|
|
- /* If the requeue was in progress, wait for it to complete */
|
|
- if (old == Q_REQUEUE_PI_IN_PROGRESS) {
|
|
-#ifdef CONFIG_PREEMPT_RT
|
|
- rcuwait_wait_event(&q->requeue_wait,
|
|
- atomic_read(&q->requeue_state) != Q_REQUEUE_PI_WAIT,
|
|
- TASK_UNINTERRUPTIBLE);
|
|
-#else
|
|
- (void)atomic_cond_read_relaxed(&q->requeue_state, VAL != Q_REQUEUE_PI_WAIT);
|
|
-#endif
|
|
- }
|
|
-
|
|
- /*
|
|
- * Requeue is now either prohibited or complete. Reread state
|
|
- * because during the wait above it might have changed. Nothing
|
|
- * will modify q->requeue_state after this point.
|
|
- */
|
|
- return atomic_read(&q->requeue_state);
|
|
-}
|
|
-
|
|
-/**
|
|
- * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue
|
|
- * @q: the futex_q
|
|
- * @key: the key of the requeue target futex
|
|
- * @hb: the hash_bucket of the requeue target futex
|
|
- *
|
|
- * During futex_requeue, with requeue_pi=1, it is possible to acquire the
|
|
- * target futex if it is uncontended or via a lock steal.
|
|
- *
|
|
- * 1) Set @q::key to the requeue target futex key so the waiter can detect
|
|
- * the wakeup on the right futex.
|
|
- *
|
|
- * 2) Dequeue @q from the hash bucket.
|
|
- *
|
|
- * 3) Set @q::rt_waiter to NULL so the woken up task can detect atomic lock
|
|
- * acquisition.
|
|
- *
|
|
- * 4) Set the q->lock_ptr to the requeue target hb->lock for the case that
|
|
- * the waiter has to fixup the pi state.
|
|
- *
|
|
- * 5) Complete the requeue state so the waiter can make progress. After
|
|
- * this point the waiter task can return from the syscall immediately in
|
|
- * case that the pi state does not have to be fixed up.
|
|
- *
|
|
- * 6) Wake the waiter task.
|
|
- *
|
|
- * Must be called with both q->lock_ptr and hb->lock held.
|
|
- */
|
|
-static inline
|
|
-void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key,
|
|
- struct futex_hash_bucket *hb)
|
|
-{
|
|
- q->key = *key;
|
|
-
|
|
- __unqueue_futex(q);
|
|
-
|
|
- WARN_ON(!q->rt_waiter);
|
|
- q->rt_waiter = NULL;
|
|
-
|
|
- q->lock_ptr = &hb->lock;
|
|
-
|
|
- /* Signal locked state to the waiter */
|
|
- futex_requeue_pi_complete(q, 1);
|
|
- wake_up_state(q->task, TASK_NORMAL);
|
|
-}
|
|
-
|
|
-/**
|
|
- * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter
|
|
- * @pifutex: the user address of the to futex
|
|
- * @hb1: the from futex hash bucket, must be locked by the caller
|
|
- * @hb2: the to futex hash bucket, must be locked by the caller
|
|
- * @key1: the from futex key
|
|
- * @key2: the to futex key
|
|
- * @ps: address to store the pi_state pointer
|
|
- * @exiting: Pointer to store the task pointer of the owner task
|
|
- * which is in the middle of exiting
|
|
- * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
|
|
- *
|
|
- * Try and get the lock on behalf of the top waiter if we can do it atomically.
|
|
- * Wake the top waiter if we succeed. If the caller specified set_waiters,
|
|
- * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit.
|
|
- * hb1 and hb2 must be held by the caller.
|
|
- *
|
|
- * @exiting is only set when the return value is -EBUSY. If so, this holds
|
|
- * a refcount on the exiting task on return and the caller needs to drop it
|
|
- * after waiting for the exit to complete.
|
|
- *
|
|
- * Return:
|
|
- * - 0 - failed to acquire the lock atomically;
|
|
- * - >0 - acquired the lock, return value is vpid of the top_waiter
|
|
- * - <0 - error
|
|
- */
|
|
-static int
|
|
-futex_proxy_trylock_atomic(u32 __user *pifutex, struct futex_hash_bucket *hb1,
|
|
- struct futex_hash_bucket *hb2, union futex_key *key1,
|
|
- union futex_key *key2, struct futex_pi_state **ps,
|
|
- struct task_struct **exiting, int set_waiters)
|
|
-{
|
|
- struct futex_q *top_waiter = NULL;
|
|
- u32 curval;
|
|
- int ret;
|
|
-
|
|
- if (get_futex_value_locked(&curval, pifutex))
|
|
- return -EFAULT;
|
|
-
|
|
- if (unlikely(should_fail_futex(true)))
|
|
- return -EFAULT;
|
|
-
|
|
- /*
|
|
- * Find the top_waiter and determine if there are additional waiters.
|
|
- * If the caller intends to requeue more than 1 waiter to pifutex,
|
|
- * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now,
|
|
- * as we have means to handle the possible fault. If not, don't set
|
|
- * the bit unnecessarily as it will force the subsequent unlock to enter
|
|
- * the kernel.
|
|
- */
|
|
- top_waiter = futex_top_waiter(hb1, key1);
|
|
-
|
|
- /* There are no waiters, nothing for us to do. */
|
|
- if (!top_waiter)
|
|
- return 0;
|
|
-
|
|
- /*
|
|
- * Ensure that this is a waiter sitting in futex_wait_requeue_pi()
|
|
- * and waiting on the 'waitqueue' futex which is always !PI.
|
|
- */
|
|
- if (!top_waiter->rt_waiter || top_waiter->pi_state)
|
|
- return -EINVAL;
|
|
-
|
|
- /* Ensure we requeue to the expected futex. */
|
|
- if (!match_futex(top_waiter->requeue_pi_key, key2))
|
|
- return -EINVAL;
|
|
-
|
|
- /* Ensure that this does not race against an early wakeup */
|
|
- if (!futex_requeue_pi_prepare(top_waiter, NULL))
|
|
- return -EAGAIN;
|
|
-
|
|
- /*
|
|
- * Try to take the lock for top_waiter and set the FUTEX_WAITERS bit
|
|
- * in the contended case or if @set_waiters is true.
|
|
- *
|
|
- * In the contended case PI state is attached to the lock owner. If
|
|
- * the user space lock can be acquired then PI state is attached to
|
|
- * the new owner (@top_waiter->task) when @set_waiters is true.
|
|
- */
|
|
- ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task,
|
|
- exiting, set_waiters);
|
|
- if (ret == 1) {
|
|
- /*
|
|
- * Lock was acquired in user space and PI state was
|
|
- * attached to @top_waiter->task. That means state is fully
|
|
- * consistent and the waiter can return to user space
|
|
- * immediately after the wakeup.
|
|
- */
|
|
- requeue_pi_wake_futex(top_waiter, key2, hb2);
|
|
- } else if (ret < 0) {
|
|
- /* Rewind top_waiter::requeue_state */
|
|
- futex_requeue_pi_complete(top_waiter, ret);
|
|
- } else {
|
|
- /*
|
|
- * futex_lock_pi_atomic() did not acquire the user space
|
|
- * futex, but managed to establish the proxy lock and pi
|
|
- * state. top_waiter::requeue_state cannot be fixed up here
|
|
- * because the waiter is not enqueued on the rtmutex
|
|
- * yet. This is handled at the callsite depending on the
|
|
- * result of rt_mutex_start_proxy_lock() which is
|
|
- * guaranteed to be reached with this function returning 0.
|
|
- */
|
|
- }
|
|
- return ret;
|
|
-}
|
|
-
|
|
-/**
|
|
- * futex_requeue() - Requeue waiters from uaddr1 to uaddr2
|
|
- * @uaddr1: source futex user address
|
|
- * @flags: futex flags (FLAGS_SHARED, etc.)
|
|
- * @uaddr2: target futex user address
|
|
- * @nr_wake: number of waiters to wake (must be 1 for requeue_pi)
|
|
- * @nr_requeue: number of waiters to requeue (0-INT_MAX)
|
|
- * @cmpval: @uaddr1 expected value (or %NULL)
|
|
- * @requeue_pi: if we are attempting to requeue from a non-pi futex to a
|
|
- * pi futex (pi to pi requeue is not supported)
|
|
- *
|
|
- * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire
|
|
- * uaddr2 atomically on behalf of the top waiter.
|
|
- *
|
|
- * Return:
|
|
- * - >=0 - on success, the number of tasks requeued or woken;
|
|
- * - <0 - on error
|
|
- */
|
|
-static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
|
|
- u32 __user *uaddr2, int nr_wake, int nr_requeue,
|
|
- u32 *cmpval, int requeue_pi)
|
|
-{
|
|
- union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
|
|
- int task_count = 0, ret;
|
|
- struct futex_pi_state *pi_state = NULL;
|
|
- struct futex_hash_bucket *hb1, *hb2;
|
|
- struct futex_q *this, *next;
|
|
- DEFINE_WAKE_Q(wake_q);
|
|
-
|
|
- if (nr_wake < 0 || nr_requeue < 0)
|
|
- return -EINVAL;
|
|
-
|
|
- /*
|
|
- * When PI not supported: return -ENOSYS if requeue_pi is true,
|
|
- * consequently the compiler knows requeue_pi is always false past
|
|
- * this point which will optimize away all the conditional code
|
|
- * further down.
|
|
- */
|
|
- if (!IS_ENABLED(CONFIG_FUTEX_PI) && requeue_pi)
|
|
- return -ENOSYS;
|
|
-
|
|
- if (requeue_pi) {
|
|
- /*
|
|
- * Requeue PI only works on two distinct uaddrs. This
|
|
- * check is only valid for private futexes. See below.
|
|
- */
|
|
- if (uaddr1 == uaddr2)
|
|
- return -EINVAL;
|
|
-
|
|
- /*
|
|
- * futex_requeue() allows the caller to define the number
|
|
- * of waiters to wake up via the @nr_wake argument. With
|
|
- * REQUEUE_PI, waking up more than one waiter is creating
|
|
- * more problems than it solves. Waking up a waiter makes
|
|
- * only sense if the PI futex @uaddr2 is uncontended as
|
|
- * this allows the requeue code to acquire the futex
|
|
- * @uaddr2 before waking the waiter. The waiter can then
|
|
- * return to user space without further action. A secondary
|
|
- * wakeup would just make the futex_wait_requeue_pi()
|
|
- * handling more complex, because that code would have to
|
|
- * look up pi_state and do more or less all the handling
|
|
- * which the requeue code has to do for the to be requeued
|
|
- * waiters. So restrict the number of waiters to wake to
|
|
- * one, and only wake it up when the PI futex is
|
|
- * uncontended. Otherwise requeue it and let the unlock of
|
|
- * the PI futex handle the wakeup.
|
|
- *
|
|
- * All REQUEUE_PI users, e.g. pthread_cond_signal() and
|
|
- * pthread_cond_broadcast() must use nr_wake=1.
|
|
- */
|
|
- if (nr_wake != 1)
|
|
- return -EINVAL;
|
|
-
|
|
- /*
|
|
- * requeue_pi requires a pi_state, try to allocate it now
|
|
- * without any locks in case it fails.
|
|
- */
|
|
- if (refill_pi_state_cache())
|
|
- return -ENOMEM;
|
|
- }
|
|
-
|
|
-retry:
|
|
- ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, FUTEX_READ);
|
|
- if (unlikely(ret != 0))
|
|
- return ret;
|
|
- ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2,
|
|
- requeue_pi ? FUTEX_WRITE : FUTEX_READ);
|
|
- if (unlikely(ret != 0))
|
|
- return ret;
|
|
-
|
|
- /*
|
|
- * The check above which compares uaddrs is not sufficient for
|
|
- * shared futexes. We need to compare the keys:
|
|
- */
|
|
- if (requeue_pi && match_futex(&key1, &key2))
|
|
- return -EINVAL;
|
|
-
|
|
- hb1 = hash_futex(&key1);
|
|
- hb2 = hash_futex(&key2);
|
|
-
|
|
-retry_private:
|
|
- hb_waiters_inc(hb2);
|
|
- double_lock_hb(hb1, hb2);
|
|
-
|
|
- if (likely(cmpval != NULL)) {
|
|
- u32 curval;
|
|
-
|
|
- ret = get_futex_value_locked(&curval, uaddr1);
|
|
-
|
|
- if (unlikely(ret)) {
|
|
- double_unlock_hb(hb1, hb2);
|
|
- hb_waiters_dec(hb2);
|
|
-
|
|
- ret = get_user(curval, uaddr1);
|
|
- if (ret)
|
|
- return ret;
|
|
-
|
|
- if (!(flags & FLAGS_SHARED))
|
|
- goto retry_private;
|
|
-
|
|
- goto retry;
|
|
- }
|
|
- if (curval != *cmpval) {
|
|
- ret = -EAGAIN;
|
|
- goto out_unlock;
|
|
- }
|
|
- }
|
|
-
|
|
- if (requeue_pi) {
|
|
- struct task_struct *exiting = NULL;
|
|
-
|
|
- /*
|
|
- * Attempt to acquire uaddr2 and wake the top waiter. If we
|
|
- * intend to requeue waiters, force setting the FUTEX_WAITERS
|
|
- * bit. We force this here where we are able to easily handle
|
|
- * faults rather in the requeue loop below.
|
|
- *
|
|
- * Updates topwaiter::requeue_state if a top waiter exists.
|
|
- */
|
|
- ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1,
|
|
- &key2, &pi_state,
|
|
- &exiting, nr_requeue);
|
|
-
|
|
- /*
|
|
- * At this point the top_waiter has either taken uaddr2 or
|
|
- * is waiting on it. In both cases pi_state has been
|
|
- * established and an initial refcount on it. In case of an
|
|
- * error there's nothing.
|
|
- *
|
|
- * The top waiter's requeue_state is up to date:
|
|
- *
|
|
- * - If the lock was acquired atomically (ret == 1), then
|
|
- * the state is Q_REQUEUE_PI_LOCKED.
|
|
- *
|
|
- * The top waiter has been dequeued and woken up and can
|
|
- * return to user space immediately. The kernel/user
|
|
- * space state is consistent. In case that there must be
|
|
- * more waiters requeued the WAITERS bit in the user
|
|
- * space futex is set so the top waiter task has to go
|
|
- * into the syscall slowpath to unlock the futex. This
|
|
- * will block until this requeue operation has been
|
|
- * completed and the hash bucket locks have been
|
|
- * dropped.
|
|
- *
|
|
- * - If the trylock failed with an error (ret < 0) then
|
|
- * the state is either Q_REQUEUE_PI_NONE, i.e. "nothing
|
|
- * happened", or Q_REQUEUE_PI_IGNORE when there was an
|
|
- * interleaved early wakeup.
|
|
- *
|
|
- * - If the trylock did not succeed (ret == 0) then the
|
|
- * state is either Q_REQUEUE_PI_IN_PROGRESS or
|
|
- * Q_REQUEUE_PI_WAIT if an early wakeup interleaved.
|
|
- * This will be cleaned up in the loop below, which
|
|
- * cannot fail because futex_proxy_trylock_atomic() did
|
|
- * the same sanity checks for requeue_pi as the loop
|
|
- * below does.
|
|
- */
|
|
- switch (ret) {
|
|
- case 0:
|
|
- /* We hold a reference on the pi state. */
|
|
- break;
|
|
-
|
|
- case 1:
|
|
- /*
|
|
- * futex_proxy_trylock_atomic() acquired the user space
|
|
- * futex. Adjust task_count.
|
|
- */
|
|
- task_count++;
|
|
- ret = 0;
|
|
- break;
|
|
-
|
|
- /*
|
|
- * If the above failed, then pi_state is NULL and
|
|
- * waiter::requeue_state is correct.
|
|
- */
|
|
- case -EFAULT:
|
|
- double_unlock_hb(hb1, hb2);
|
|
- hb_waiters_dec(hb2);
|
|
- ret = fault_in_user_writeable(uaddr2);
|
|
- if (!ret)
|
|
- goto retry;
|
|
- return ret;
|
|
- case -EBUSY:
|
|
- case -EAGAIN:
|
|
- /*
|
|
- * Two reasons for this:
|
|
- * - EBUSY: Owner is exiting and we just wait for the
|
|
- * exit to complete.
|
|
- * - EAGAIN: The user space value changed.
|
|
- */
|
|
- double_unlock_hb(hb1, hb2);
|
|
- hb_waiters_dec(hb2);
|
|
- /*
|
|
- * Handle the case where the owner is in the middle of
|
|
- * exiting. Wait for the exit to complete otherwise
|
|
- * this task might loop forever, aka. live lock.
|
|
- */
|
|
- wait_for_owner_exiting(ret, exiting);
|
|
- cond_resched();
|
|
- goto retry;
|
|
- default:
|
|
- goto out_unlock;
|
|
- }
|
|
- }
|
|
-
|
|
- plist_for_each_entry_safe(this, next, &hb1->chain, list) {
|
|
- if (task_count - nr_wake >= nr_requeue)
|
|
- break;
|
|
-
|
|
- if (!match_futex(&this->key, &key1))
|
|
- continue;
|
|
-
|
|
- /*
|
|
- * FUTEX_WAIT_REQUEUE_PI and FUTEX_CMP_REQUEUE_PI should always
|
|
- * be paired with each other and no other futex ops.
|
|
- *
|
|
- * We should never be requeueing a futex_q with a pi_state,
|
|
- * which is awaiting a futex_unlock_pi().
|
|
- */
|
|
- if ((requeue_pi && !this->rt_waiter) ||
|
|
- (!requeue_pi && this->rt_waiter) ||
|
|
- this->pi_state) {
|
|
- ret = -EINVAL;
|
|
- break;
|
|
- }
|
|
-
|
|
- /* Plain futexes just wake or requeue and are done */
|
|
- if (!requeue_pi) {
|
|
- if (++task_count <= nr_wake)
|
|
- mark_wake_futex(&wake_q, this);
|
|
- else
|
|
- requeue_futex(this, hb1, hb2, &key2);
|
|
- continue;
|
|
- }
|
|
-
|
|
- /* Ensure we requeue to the expected futex for requeue_pi. */
|
|
- if (!match_futex(this->requeue_pi_key, &key2)) {
|
|
- ret = -EINVAL;
|
|
- break;
|
|
- }
|
|
-
|
|
- /*
|
|
- * Requeue nr_requeue waiters and possibly one more in the case
|
|
- * of requeue_pi if we couldn't acquire the lock atomically.
|
|
- *
|
|
- * Prepare the waiter to take the rt_mutex. Take a refcount
|
|
- * on the pi_state and store the pointer in the futex_q
|
|
- * object of the waiter.
|
|
- */
|
|
- get_pi_state(pi_state);
|
|
-
|
|
- /* Don't requeue when the waiter is already on the way out. */
|
|
- if (!futex_requeue_pi_prepare(this, pi_state)) {
|
|
- /*
|
|
- * Early woken waiter signaled that it is on the
|
|
- * way out. Drop the pi_state reference and try the
|
|
- * next waiter. @this->pi_state is still NULL.
|
|
- */
|
|
- put_pi_state(pi_state);
|
|
- continue;
|
|
- }
|
|
-
|
|
- ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex,
|
|
- this->rt_waiter,
|
|
- this->task);
|
|
-
|
|
- if (ret == 1) {
|
|
- /*
|
|
- * We got the lock. We do neither drop the refcount
|
|
- * on pi_state nor clear this->pi_state because the
|
|
- * waiter needs the pi_state for cleaning up the
|
|
- * user space value. It will drop the refcount
|
|
- * after doing so. this::requeue_state is updated
|
|
- * in the wakeup as well.
|
|
- */
|
|
- requeue_pi_wake_futex(this, &key2, hb2);
|
|
- task_count++;
|
|
- } else if (!ret) {
|
|
- /* Waiter is queued, move it to hb2 */
|
|
- requeue_futex(this, hb1, hb2, &key2);
|
|
- futex_requeue_pi_complete(this, 0);
|
|
- task_count++;
|
|
- } else {
|
|
- /*
|
|
- * rt_mutex_start_proxy_lock() detected a potential
|
|
- * deadlock when we tried to queue that waiter.
|
|
- * Drop the pi_state reference which we took above
|
|
- * and remove the pointer to the state from the
|
|
- * waiters futex_q object.
|
|
- */
|
|
- this->pi_state = NULL;
|
|
- put_pi_state(pi_state);
|
|
- futex_requeue_pi_complete(this, ret);
|
|
- /*
|
|
- * We stop queueing more waiters and let user space
|
|
- * deal with the mess.
|
|
- */
|
|
- break;
|
|
- }
|
|
- }
|
|
-
|
|
- /*
|
|
- * We took an extra initial reference to the pi_state in
|
|
- * futex_proxy_trylock_atomic(). We need to drop it here again.
|
|
- */
|
|
- put_pi_state(pi_state);
|
|
-
|
|
-out_unlock:
|
|
- double_unlock_hb(hb1, hb2);
|
|
- wake_up_q(&wake_q);
|
|
- hb_waiters_dec(hb2);
|
|
- return ret ? ret : task_count;
|
|
-}
|
|
-
|
|
-/* The key must be already stored in q->key. */
|
|
-static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
|
|
- __acquires(&hb->lock)
|
|
-{
|
|
- struct futex_hash_bucket *hb;
|
|
-
|
|
- hb = hash_futex(&q->key);
|
|
-
|
|
- /*
|
|
- * Increment the counter before taking the lock so that
|
|
- * a potential waker won't miss a to-be-slept task that is
|
|
- * waiting for the spinlock. This is safe as all queue_lock()
|
|
- * users end up calling queue_me(). Similarly, for housekeeping,
|
|
- * decrement the counter at queue_unlock() when some error has
|
|
- * occurred and we don't end up adding the task to the list.
|
|
- */
|
|
- hb_waiters_inc(hb); /* implies smp_mb(); (A) */
|
|
-
|
|
- q->lock_ptr = &hb->lock;
|
|
-
|
|
- spin_lock(&hb->lock);
|
|
- return hb;
|
|
-}
|
|
-
|
|
-static inline void
|
|
-queue_unlock(struct futex_hash_bucket *hb)
|
|
- __releases(&hb->lock)
|
|
-{
|
|
- spin_unlock(&hb->lock);
|
|
- hb_waiters_dec(hb);
|
|
-}
|
|
-
|
|
-static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
|
|
-{
|
|
- int prio;
|
|
-
|
|
- /*
|
|
- * The priority used to register this element is
|
|
- * - either the real thread-priority for the real-time threads
|
|
- * (i.e. threads with a priority lower than MAX_RT_PRIO)
|
|
- * - or MAX_RT_PRIO for non-RT threads.
|
|
- * Thus, all RT-threads are woken first in priority order, and
|
|
- * the others are woken last, in FIFO order.
|
|
- */
|
|
- prio = min(current->normal_prio, MAX_RT_PRIO);
|
|
-
|
|
- plist_node_init(&q->list, prio);
|
|
- plist_add(&q->list, &hb->chain);
|
|
- q->task = current;
|
|
-}
|
|
-
|
|
-/**
|
|
- * queue_me() - Enqueue the futex_q on the futex_hash_bucket
|
|
- * @q: The futex_q to enqueue
|
|
- * @hb: The destination hash bucket
|
|
- *
|
|
- * The hb->lock must be held by the caller, and is released here. A call to
|
|
- * queue_me() is typically paired with exactly one call to unqueue_me(). The
|
|
- * exceptions involve the PI related operations, which may use unqueue_me_pi()
|
|
- * or nothing if the unqueue is done as part of the wake process and the unqueue
|
|
- * state is implicit in the state of woken task (see futex_wait_requeue_pi() for
|
|
- * an example).
|
|
- */
|
|
-static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
|
|
- __releases(&hb->lock)
|
|
-{
|
|
- __queue_me(q, hb);
|
|
- spin_unlock(&hb->lock);
|
|
-}
|
|
-
|
|
-/**
|
|
- * unqueue_me() - Remove the futex_q from its futex_hash_bucket
|
|
- * @q: The futex_q to unqueue
|
|
- *
|
|
- * The q->lock_ptr must not be held by the caller. A call to unqueue_me() must
|
|
- * be paired with exactly one earlier call to queue_me().
|
|
- *
|
|
- * Return:
|
|
- * - 1 - if the futex_q was still queued (and we removed unqueued it);
|
|
- * - 0 - if the futex_q was already removed by the waking thread
|
|
- */
|
|
-static int unqueue_me(struct futex_q *q)
|
|
-{
|
|
- spinlock_t *lock_ptr;
|
|
- int ret = 0;
|
|
-
|
|
- /* In the common case we don't take the spinlock, which is nice. */
|
|
-retry:
|
|
- /*
|
|
- * q->lock_ptr can change between this read and the following spin_lock.
|
|
- * Use READ_ONCE to forbid the compiler from reloading q->lock_ptr and
|
|
- * optimizing lock_ptr out of the logic below.
|
|
- */
|
|
- lock_ptr = READ_ONCE(q->lock_ptr);
|
|
- if (lock_ptr != NULL) {
|
|
- spin_lock(lock_ptr);
|
|
- /*
|
|
- * q->lock_ptr can change between reading it and
|
|
- * spin_lock(), causing us to take the wrong lock. This
|
|
- * corrects the race condition.
|
|
- *
|
|
- * Reasoning goes like this: if we have the wrong lock,
|
|
- * q->lock_ptr must have changed (maybe several times)
|
|
- * between reading it and the spin_lock(). It can
|
|
- * change again after the spin_lock() but only if it was
|
|
- * already changed before the spin_lock(). It cannot,
|
|
- * however, change back to the original value. Therefore
|
|
- * we can detect whether we acquired the correct lock.
|
|
- */
|
|
- if (unlikely(lock_ptr != q->lock_ptr)) {
|
|
- spin_unlock(lock_ptr);
|
|
- goto retry;
|
|
- }
|
|
- __unqueue_futex(q);
|
|
-
|
|
- BUG_ON(q->pi_state);
|
|
-
|
|
- spin_unlock(lock_ptr);
|
|
- ret = 1;
|
|
- }
|
|
-
|
|
- return ret;
|
|
-}
|
|
-
|
|
-/*
|
|
- * PI futexes can not be requeued and must remove themselves from the
|
|
- * hash bucket. The hash bucket lock (i.e. lock_ptr) is held.
|
|
- */
|
|
-static void unqueue_me_pi(struct futex_q *q)
|
|
-{
|
|
- __unqueue_futex(q);
|
|
-
|
|
- BUG_ON(!q->pi_state);
|
|
- put_pi_state(q->pi_state);
|
|
- q->pi_state = NULL;
|
|
-}
|
|
-
|
|
-static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
|
|
- struct task_struct *argowner)
|
|
-{
|
|
- struct futex_pi_state *pi_state = q->pi_state;
|
|
- struct task_struct *oldowner, *newowner;
|
|
- u32 uval, curval, newval, newtid;
|
|
- int err = 0;
|
|
-
|
|
- oldowner = pi_state->owner;
|
|
-
|
|
- /*
|
|
- * We are here because either:
|
|
- *
|
|
- * - we stole the lock and pi_state->owner needs updating to reflect
|
|
- * that (@argowner == current),
|
|
- *
|
|
- * or:
|
|
- *
|
|
- * - someone stole our lock and we need to fix things to point to the
|
|
- * new owner (@argowner == NULL).
|
|
- *
|
|
- * Either way, we have to replace the TID in the user space variable.
|
|
- * This must be atomic as we have to preserve the owner died bit here.
|
|
- *
|
|
- * Note: We write the user space value _before_ changing the pi_state
|
|
- * because we can fault here. Imagine swapped out pages or a fork
|
|
- * that marked all the anonymous memory readonly for cow.
|
|
- *
|
|
- * Modifying pi_state _before_ the user space value would leave the
|
|
- * pi_state in an inconsistent state when we fault here, because we
|
|
- * need to drop the locks to handle the fault. This might be observed
|
|
- * in the PID checks when attaching to PI state .
|
|
- */
|
|
-retry:
|
|
- if (!argowner) {
|
|
- if (oldowner != current) {
|
|
- /*
|
|
- * We raced against a concurrent self; things are
|
|
- * already fixed up. Nothing to do.
|
|
- */
|
|
- return 0;
|
|
- }
|
|
-
|
|
- if (__rt_mutex_futex_trylock(&pi_state->pi_mutex)) {
|
|
- /* We got the lock. pi_state is correct. Tell caller. */
|
|
- return 1;
|
|
- }
|
|
-
|
|
- /*
|
|
- * The trylock just failed, so either there is an owner or
|
|
- * there is a higher priority waiter than this one.
|
|
- */
|
|
- newowner = rt_mutex_owner(&pi_state->pi_mutex);
|
|
- /*
|
|
- * If the higher priority waiter has not yet taken over the
|
|
- * rtmutex then newowner is NULL. We can't return here with
|
|
- * that state because it's inconsistent vs. the user space
|
|
- * state. So drop the locks and try again. It's a valid
|
|
- * situation and not any different from the other retry
|
|
- * conditions.
|
|
- */
|
|
- if (unlikely(!newowner)) {
|
|
- err = -EAGAIN;
|
|
- goto handle_err;
|
|
- }
|
|
- } else {
|
|
- WARN_ON_ONCE(argowner != current);
|
|
- if (oldowner == current) {
|
|
- /*
|
|
- * We raced against a concurrent self; things are
|
|
- * already fixed up. Nothing to do.
|
|
- */
|
|
- return 1;
|
|
- }
|
|
- newowner = argowner;
|
|
- }
|
|
-
|
|
- newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
|
|
- /* Owner died? */
|
|
- if (!pi_state->owner)
|
|
- newtid |= FUTEX_OWNER_DIED;
|
|
-
|
|
- err = get_futex_value_locked(&uval, uaddr);
|
|
- if (err)
|
|
- goto handle_err;
|
|
-
|
|
- for (;;) {
|
|
- newval = (uval & FUTEX_OWNER_DIED) | newtid;
|
|
-
|
|
- err = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
|
|
- if (err)
|
|
- goto handle_err;
|
|
-
|
|
- if (curval == uval)
|
|
- break;
|
|
- uval = curval;
|
|
- }
|
|
-
|
|
- /*
|
|
- * We fixed up user space. Now we need to fix the pi_state
|
|
- * itself.
|
|
- */
|
|
- pi_state_update_owner(pi_state, newowner);
|
|
-
|
|
- return argowner == current;
|
|
-
|
|
- /*
|
|
- * In order to reschedule or handle a page fault, we need to drop the
|
|
- * locks here. In the case of a fault, this gives the other task
|
|
- * (either the highest priority waiter itself or the task which stole
|
|
- * the rtmutex) the chance to try the fixup of the pi_state. So once we
|
|
- * are back from handling the fault we need to check the pi_state after
|
|
- * reacquiring the locks and before trying to do another fixup. When
|
|
- * the fixup has been done already we simply return.
|
|
- *
|
|
- * Note: we hold both hb->lock and pi_mutex->wait_lock. We can safely
|
|
- * drop hb->lock since the caller owns the hb -> futex_q relation.
|
|
- * Dropping the pi_mutex->wait_lock requires the state revalidate.
|
|
- */
|
|
-handle_err:
|
|
- raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
- spin_unlock(q->lock_ptr);
|
|
-
|
|
- switch (err) {
|
|
- case -EFAULT:
|
|
- err = fault_in_user_writeable(uaddr);
|
|
- break;
|
|
-
|
|
- case -EAGAIN:
|
|
- cond_resched();
|
|
- err = 0;
|
|
- break;
|
|
-
|
|
- default:
|
|
- WARN_ON_ONCE(1);
|
|
- break;
|
|
- }
|
|
-
|
|
- spin_lock(q->lock_ptr);
|
|
- raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
-
|
|
- /*
|
|
- * Check if someone else fixed it for us:
|
|
- */
|
|
- if (pi_state->owner != oldowner)
|
|
- return argowner == current;
|
|
-
|
|
- /* Retry if err was -EAGAIN or the fault in succeeded */
|
|
- if (!err)
|
|
- goto retry;
|
|
-
|
|
- /*
|
|
- * fault_in_user_writeable() failed so user state is immutable. At
|
|
- * best we can make the kernel state consistent but user state will
|
|
- * be most likely hosed and any subsequent unlock operation will be
|
|
- * rejected due to PI futex rule [10].
|
|
- *
|
|
- * Ensure that the rtmutex owner is also the pi_state owner despite
|
|
- * the user space value claiming something different. There is no
|
|
- * point in unlocking the rtmutex if current is the owner as it
|
|
- * would need to wait until the next waiter has taken the rtmutex
|
|
- * to guarantee consistent state. Keep it simple. Userspace asked
|
|
- * for this wreckaged state.
|
|
- *
|
|
- * The rtmutex has an owner - either current or some other
|
|
- * task. See the EAGAIN loop above.
|
|
- */
|
|
- pi_state_update_owner(pi_state, rt_mutex_owner(&pi_state->pi_mutex));
|
|
-
|
|
- return err;
|
|
-}
|
|
-
|
|
-static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
|
|
- struct task_struct *argowner)
|
|
-{
|
|
- struct futex_pi_state *pi_state = q->pi_state;
|
|
- int ret;
|
|
-
|
|
- lockdep_assert_held(q->lock_ptr);
|
|
-
|
|
- raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
- ret = __fixup_pi_state_owner(uaddr, q, argowner);
|
|
- raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
- return ret;
|
|
-}
|
|
-
|
|
-static long futex_wait_restart(struct restart_block *restart);
|
|
-
|
|
-/**
|
|
- * fixup_owner() - Post lock pi_state and corner case management
|
|
- * @uaddr: user address of the futex
|
|
- * @q: futex_q (contains pi_state and access to the rt_mutex)
|
|
- * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0)
|
|
- *
|
|
- * After attempting to lock an rt_mutex, this function is called to cleanup
|
|
- * the pi_state owner as well as handle race conditions that may allow us to
|
|
- * acquire the lock. Must be called with the hb lock held.
|
|
- *
|
|
- * Return:
|
|
- * - 1 - success, lock taken;
|
|
- * - 0 - success, lock not taken;
|
|
- * - <0 - on error (-EFAULT)
|
|
- */
|
|
-static int fixup_owner(u32 __user *uaddr, struct futex_q *q, int locked)
|
|
-{
|
|
- if (locked) {
|
|
- /*
|
|
- * Got the lock. We might not be the anticipated owner if we
|
|
- * did a lock-steal - fix up the PI-state in that case:
|
|
- *
|
|
- * Speculative pi_state->owner read (we don't hold wait_lock);
|
|
- * since we own the lock pi_state->owner == current is the
|
|
- * stable state, anything else needs more attention.
|
|
- */
|
|
- if (q->pi_state->owner != current)
|
|
- return fixup_pi_state_owner(uaddr, q, current);
|
|
- return 1;
|
|
- }
|
|
-
|
|
- /*
|
|
- * If we didn't get the lock; check if anybody stole it from us. In
|
|
- * that case, we need to fix up the uval to point to them instead of
|
|
- * us, otherwise bad things happen. [10]
|
|
- *
|
|
- * Another speculative read; pi_state->owner == current is unstable
|
|
- * but needs our attention.
|
|
- */
|
|
- if (q->pi_state->owner == current)
|
|
- return fixup_pi_state_owner(uaddr, q, NULL);
|
|
-
|
|
- /*
|
|
- * Paranoia check. If we did not take the lock, then we should not be
|
|
- * the owner of the rt_mutex. Warn and establish consistent state.
|
|
- */
|
|
- if (WARN_ON_ONCE(rt_mutex_owner(&q->pi_state->pi_mutex) == current))
|
|
- return fixup_pi_state_owner(uaddr, q, current);
|
|
-
|
|
- return 0;
|
|
-}
|
|
-
|
|
-/**
|
|
- * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal
|
|
- * @hb: the futex hash bucket, must be locked by the caller
|
|
- * @q: the futex_q to queue up on
|
|
- * @timeout: the prepared hrtimer_sleeper, or null for no timeout
|
|
- */
|
|
-static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
|
|
- struct hrtimer_sleeper *timeout)
|
|
-{
|
|
- /*
|
|
- * The task state is guaranteed to be set before another task can
|
|
- * wake it. set_current_state() is implemented using smp_store_mb() and
|
|
- * queue_me() calls spin_unlock() upon completion, both serializing
|
|
- * access to the hash list and forcing another memory barrier.
|
|
- */
|
|
- set_current_state(TASK_INTERRUPTIBLE);
|
|
- queue_me(q, hb);
|
|
-
|
|
- /* Arm the timer */
|
|
- if (timeout)
|
|
- hrtimer_sleeper_start_expires(timeout, HRTIMER_MODE_ABS);
|
|
-
|
|
- /*
|
|
- * If we have been removed from the hash list, then another task
|
|
- * has tried to wake us, and we can skip the call to schedule().
|
|
- */
|
|
- if (likely(!plist_node_empty(&q->list))) {
|
|
- /*
|
|
- * If the timer has already expired, current will already be
|
|
- * flagged for rescheduling. Only call schedule if there
|
|
- * is no timeout, or if it has yet to expire.
|
|
- */
|
|
- if (!timeout || timeout->task)
|
|
- freezable_schedule();
|
|
- }
|
|
- __set_current_state(TASK_RUNNING);
|
|
-}
|
|
-
|
|
-/**
|
|
- * futex_wait_setup() - Prepare to wait on a futex
|
|
- * @uaddr: the futex userspace address
|
|
- * @val: the expected value
|
|
- * @flags: futex flags (FLAGS_SHARED, etc.)
|
|
- * @q: the associated futex_q
|
|
- * @hb: storage for hash_bucket pointer to be returned to caller
|
|
- *
|
|
- * Setup the futex_q and locate the hash_bucket. Get the futex value and
|
|
- * compare it with the expected value. Handle atomic faults internally.
|
|
- * Return with the hb lock held on success, and unlocked on failure.
|
|
- *
|
|
- * Return:
|
|
- * - 0 - uaddr contains val and hb has been locked;
|
|
- * - <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked
|
|
- */
|
|
-static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
|
|
- struct futex_q *q, struct futex_hash_bucket **hb)
|
|
-{
|
|
- u32 uval;
|
|
- int ret;
|
|
-
|
|
- /*
|
|
- * Access the page AFTER the hash-bucket is locked.
|
|
- * Order is important:
|
|
- *
|
|
- * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
|
|
- * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
|
|
- *
|
|
- * The basic logical guarantee of a futex is that it blocks ONLY
|
|
- * if cond(var) is known to be true at the time of blocking, for
|
|
- * any cond. If we locked the hash-bucket after testing *uaddr, that
|
|
- * would open a race condition where we could block indefinitely with
|
|
- * cond(var) false, which would violate the guarantee.
|
|
- *
|
|
- * On the other hand, we insert q and release the hash-bucket only
|
|
- * after testing *uaddr. This guarantees that futex_wait() will NOT
|
|
- * absorb a wakeup if *uaddr does not match the desired values
|
|
- * while the syscall executes.
|
|
- */
|
|
-retry:
|
|
- ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, FUTEX_READ);
|
|
- if (unlikely(ret != 0))
|
|
- return ret;
|
|
-
|
|
-retry_private:
|
|
- *hb = queue_lock(q);
|
|
-
|
|
- ret = get_futex_value_locked(&uval, uaddr);
|
|
-
|
|
- if (ret) {
|
|
- queue_unlock(*hb);
|
|
-
|
|
- ret = get_user(uval, uaddr);
|
|
- if (ret)
|
|
- return ret;
|
|
-
|
|
- if (!(flags & FLAGS_SHARED))
|
|
- goto retry_private;
|
|
-
|
|
- goto retry;
|
|
- }
|
|
-
|
|
- if (uval != val) {
|
|
- queue_unlock(*hb);
|
|
- ret = -EWOULDBLOCK;
|
|
- }
|
|
-
|
|
- return ret;
|
|
-}
|
|
-
|
|
-static int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
|
|
- ktime_t *abs_time, u32 bitset)
|
|
-{
|
|
- struct hrtimer_sleeper timeout, *to;
|
|
- struct restart_block *restart;
|
|
- struct futex_hash_bucket *hb;
|
|
- struct futex_q q = futex_q_init;
|
|
- int ret;
|
|
-
|
|
- if (!bitset)
|
|
- return -EINVAL;
|
|
- q.bitset = bitset;
|
|
-
|
|
- to = futex_setup_timer(abs_time, &timeout, flags,
|
|
- current->timer_slack_ns);
|
|
-retry:
|
|
- /*
|
|
- * Prepare to wait on uaddr. On success, it holds hb->lock and q
|
|
- * is initialized.
|
|
- */
|
|
- ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
|
|
- if (ret)
|
|
- goto out;
|
|
-
|
|
- /* queue_me and wait for wakeup, timeout, or a signal. */
|
|
- futex_wait_queue_me(hb, &q, to);
|
|
-
|
|
- /* If we were woken (and unqueued), we succeeded, whatever. */
|
|
- ret = 0;
|
|
- if (!unqueue_me(&q))
|
|
- goto out;
|
|
- ret = -ETIMEDOUT;
|
|
- if (to && !to->task)
|
|
- goto out;
|
|
-
|
|
- /*
|
|
- * We expect signal_pending(current), but we might be the
|
|
- * victim of a spurious wakeup as well.
|
|
- */
|
|
- if (!signal_pending(current))
|
|
- goto retry;
|
|
-
|
|
- ret = -ERESTARTSYS;
|
|
- if (!abs_time)
|
|
- goto out;
|
|
-
|
|
- restart = ¤t->restart_block;
|
|
- restart->futex.uaddr = uaddr;
|
|
- restart->futex.val = val;
|
|
- restart->futex.time = *abs_time;
|
|
- restart->futex.bitset = bitset;
|
|
- restart->futex.flags = flags | FLAGS_HAS_TIMEOUT;
|
|
-
|
|
- ret = set_restart_fn(restart, futex_wait_restart);
|
|
-
|
|
-out:
|
|
- if (to) {
|
|
- hrtimer_cancel(&to->timer);
|
|
- destroy_hrtimer_on_stack(&to->timer);
|
|
- }
|
|
- return ret;
|
|
-}
|
|
-
|
|
-
|
|
-static long futex_wait_restart(struct restart_block *restart)
|
|
-{
|
|
- u32 __user *uaddr = restart->futex.uaddr;
|
|
- ktime_t t, *tp = NULL;
|
|
-
|
|
- if (restart->futex.flags & FLAGS_HAS_TIMEOUT) {
|
|
- t = restart->futex.time;
|
|
- tp = &t;
|
|
- }
|
|
- restart->fn = do_no_restart_syscall;
|
|
-
|
|
- return (long)futex_wait(uaddr, restart->futex.flags,
|
|
- restart->futex.val, tp, restart->futex.bitset);
|
|
-}
|
|
-
|
|
-
|
|
-/*
|
|
- * Userspace tried a 0 -> TID atomic transition of the futex value
|
|
- * and failed. The kernel side here does the whole locking operation:
|
|
- * if there are waiters then it will block as a consequence of relying
|
|
- * on rt-mutexes, it does PI, etc. (Due to races the kernel might see
|
|
- * a 0 value of the futex too.).
|
|
- *
|
|
- * Also serves as futex trylock_pi()'ing, and due semantics.
|
|
- */
|
|
-static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
|
|
- ktime_t *time, int trylock)
|
|
-{
|
|
- struct hrtimer_sleeper timeout, *to;
|
|
- struct task_struct *exiting = NULL;
|
|
- struct rt_mutex_waiter rt_waiter;
|
|
- struct futex_hash_bucket *hb;
|
|
- struct futex_q q = futex_q_init;
|
|
- int res, ret;
|
|
-
|
|
- if (!IS_ENABLED(CONFIG_FUTEX_PI))
|
|
- return -ENOSYS;
|
|
-
|
|
- if (refill_pi_state_cache())
|
|
- return -ENOMEM;
|
|
-
|
|
- to = futex_setup_timer(time, &timeout, flags, 0);
|
|
-
|
|
-retry:
|
|
- ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, FUTEX_WRITE);
|
|
- if (unlikely(ret != 0))
|
|
- goto out;
|
|
-
|
|
-retry_private:
|
|
- hb = queue_lock(&q);
|
|
-
|
|
- ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current,
|
|
- &exiting, 0);
|
|
- if (unlikely(ret)) {
|
|
- /*
|
|
- * Atomic work succeeded and we got the lock,
|
|
- * or failed. Either way, we do _not_ block.
|
|
- */
|
|
- switch (ret) {
|
|
- case 1:
|
|
- /* We got the lock. */
|
|
- ret = 0;
|
|
- goto out_unlock_put_key;
|
|
- case -EFAULT:
|
|
- goto uaddr_faulted;
|
|
- case -EBUSY:
|
|
- case -EAGAIN:
|
|
- /*
|
|
- * Two reasons for this:
|
|
- * - EBUSY: Task is exiting and we just wait for the
|
|
- * exit to complete.
|
|
- * - EAGAIN: The user space value changed.
|
|
- */
|
|
- queue_unlock(hb);
|
|
- /*
|
|
- * Handle the case where the owner is in the middle of
|
|
- * exiting. Wait for the exit to complete otherwise
|
|
- * this task might loop forever, aka. live lock.
|
|
- */
|
|
- wait_for_owner_exiting(ret, exiting);
|
|
- cond_resched();
|
|
- goto retry;
|
|
- default:
|
|
- goto out_unlock_put_key;
|
|
- }
|
|
- }
|
|
-
|
|
- WARN_ON(!q.pi_state);
|
|
-
|
|
- /*
|
|
- * Only actually queue now that the atomic ops are done:
|
|
- */
|
|
- __queue_me(&q, hb);
|
|
-
|
|
- if (trylock) {
|
|
- ret = rt_mutex_futex_trylock(&q.pi_state->pi_mutex);
|
|
- /* Fixup the trylock return value: */
|
|
- ret = ret ? 0 : -EWOULDBLOCK;
|
|
- goto no_block;
|
|
- }
|
|
-
|
|
- rt_mutex_init_waiter(&rt_waiter);
|
|
-
|
|
- /*
|
|
- * On PREEMPT_RT_FULL, when hb->lock becomes an rt_mutex, we must not
|
|
- * hold it while doing rt_mutex_start_proxy(), because then it will
|
|
- * include hb->lock in the blocking chain, even through we'll not in
|
|
- * fact hold it while blocking. This will lead it to report -EDEADLK
|
|
- * and BUG when futex_unlock_pi() interleaves with this.
|
|
- *
|
|
- * Therefore acquire wait_lock while holding hb->lock, but drop the
|
|
- * latter before calling __rt_mutex_start_proxy_lock(). This
|
|
- * interleaves with futex_unlock_pi() -- which does a similar lock
|
|
- * handoff -- such that the latter can observe the futex_q::pi_state
|
|
- * before __rt_mutex_start_proxy_lock() is done.
|
|
- */
|
|
- raw_spin_lock_irq(&q.pi_state->pi_mutex.wait_lock);
|
|
- spin_unlock(q.lock_ptr);
|
|
- /*
|
|
- * __rt_mutex_start_proxy_lock() unconditionally enqueues the @rt_waiter
|
|
- * such that futex_unlock_pi() is guaranteed to observe the waiter when
|
|
- * it sees the futex_q::pi_state.
|
|
- */
|
|
- ret = __rt_mutex_start_proxy_lock(&q.pi_state->pi_mutex, &rt_waiter, current);
|
|
- raw_spin_unlock_irq(&q.pi_state->pi_mutex.wait_lock);
|
|
-
|
|
- if (ret) {
|
|
- if (ret == 1)
|
|
- ret = 0;
|
|
- goto cleanup;
|
|
- }
|
|
-
|
|
- if (unlikely(to))
|
|
- hrtimer_sleeper_start_expires(to, HRTIMER_MODE_ABS);
|
|
-
|
|
- ret = rt_mutex_wait_proxy_lock(&q.pi_state->pi_mutex, to, &rt_waiter);
|
|
-
|
|
-cleanup:
|
|
- spin_lock(q.lock_ptr);
|
|
- /*
|
|
- * If we failed to acquire the lock (deadlock/signal/timeout), we must
|
|
- * first acquire the hb->lock before removing the lock from the
|
|
- * rt_mutex waitqueue, such that we can keep the hb and rt_mutex wait
|
|
- * lists consistent.
|
|
- *
|
|
- * In particular; it is important that futex_unlock_pi() can not
|
|
- * observe this inconsistency.
|
|
- */
|
|
- if (ret && !rt_mutex_cleanup_proxy_lock(&q.pi_state->pi_mutex, &rt_waiter))
|
|
- ret = 0;
|
|
-
|
|
-no_block:
|
|
- /*
|
|
- * Fixup the pi_state owner and possibly acquire the lock if we
|
|
- * haven't already.
|
|
- */
|
|
- res = fixup_owner(uaddr, &q, !ret);
|
|
- /*
|
|
- * If fixup_owner() returned an error, propagate that. If it acquired
|
|
- * the lock, clear our -ETIMEDOUT or -EINTR.
|
|
- */
|
|
- if (res)
|
|
- ret = (res < 0) ? res : 0;
|
|
-
|
|
- unqueue_me_pi(&q);
|
|
- spin_unlock(q.lock_ptr);
|
|
- goto out;
|
|
-
|
|
-out_unlock_put_key:
|
|
- queue_unlock(hb);
|
|
-
|
|
-out:
|
|
- if (to) {
|
|
- hrtimer_cancel(&to->timer);
|
|
- destroy_hrtimer_on_stack(&to->timer);
|
|
- }
|
|
- return ret != -EINTR ? ret : -ERESTARTNOINTR;
|
|
-
|
|
-uaddr_faulted:
|
|
- queue_unlock(hb);
|
|
-
|
|
- ret = fault_in_user_writeable(uaddr);
|
|
- if (ret)
|
|
- goto out;
|
|
-
|
|
- if (!(flags & FLAGS_SHARED))
|
|
- goto retry_private;
|
|
-
|
|
- goto retry;
|
|
-}
|
|
-
|
|
-/*
|
|
- * Userspace attempted a TID -> 0 atomic transition, and failed.
|
|
- * This is the in-kernel slowpath: we look up the PI state (if any),
|
|
- * and do the rt-mutex unlock.
|
|
- */
|
|
-static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags)
|
|
-{
|
|
- u32 curval, uval, vpid = task_pid_vnr(current);
|
|
- union futex_key key = FUTEX_KEY_INIT;
|
|
- struct futex_hash_bucket *hb;
|
|
- struct futex_q *top_waiter;
|
|
- int ret;
|
|
-
|
|
- if (!IS_ENABLED(CONFIG_FUTEX_PI))
|
|
- return -ENOSYS;
|
|
-
|
|
-retry:
|
|
- if (get_user(uval, uaddr))
|
|
- return -EFAULT;
|
|
- /*
|
|
- * We release only a lock we actually own:
|
|
- */
|
|
- if ((uval & FUTEX_TID_MASK) != vpid)
|
|
- return -EPERM;
|
|
-
|
|
- ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, FUTEX_WRITE);
|
|
- if (ret)
|
|
- return ret;
|
|
-
|
|
- hb = hash_futex(&key);
|
|
- spin_lock(&hb->lock);
|
|
-
|
|
- /*
|
|
- * Check waiters first. We do not trust user space values at
|
|
- * all and we at least want to know if user space fiddled
|
|
- * with the futex value instead of blindly unlocking.
|
|
- */
|
|
- top_waiter = futex_top_waiter(hb, &key);
|
|
- if (top_waiter) {
|
|
- struct futex_pi_state *pi_state = top_waiter->pi_state;
|
|
-
|
|
- ret = -EINVAL;
|
|
- if (!pi_state)
|
|
- goto out_unlock;
|
|
-
|
|
- /*
|
|
- * If current does not own the pi_state then the futex is
|
|
- * inconsistent and user space fiddled with the futex value.
|
|
- */
|
|
- if (pi_state->owner != current)
|
|
- goto out_unlock;
|
|
-
|
|
- get_pi_state(pi_state);
|
|
- /*
|
|
- * By taking wait_lock while still holding hb->lock, we ensure
|
|
- * there is no point where we hold neither; and therefore
|
|
- * wake_futex_pi() must observe a state consistent with what we
|
|
- * observed.
|
|
- *
|
|
- * In particular; this forces __rt_mutex_start_proxy() to
|
|
- * complete such that we're guaranteed to observe the
|
|
- * rt_waiter. Also see the WARN in wake_futex_pi().
|
|
- */
|
|
- raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
- spin_unlock(&hb->lock);
|
|
-
|
|
- /* drops pi_state->pi_mutex.wait_lock */
|
|
- ret = wake_futex_pi(uaddr, uval, pi_state);
|
|
-
|
|
- put_pi_state(pi_state);
|
|
-
|
|
- /*
|
|
- * Success, we're done! No tricky corner cases.
|
|
- */
|
|
- if (!ret)
|
|
- return ret;
|
|
- /*
|
|
- * The atomic access to the futex value generated a
|
|
- * pagefault, so retry the user-access and the wakeup:
|
|
- */
|
|
- if (ret == -EFAULT)
|
|
- goto pi_faulted;
|
|
- /*
|
|
- * A unconditional UNLOCK_PI op raced against a waiter
|
|
- * setting the FUTEX_WAITERS bit. Try again.
|
|
- */
|
|
- if (ret == -EAGAIN)
|
|
- goto pi_retry;
|
|
- /*
|
|
- * wake_futex_pi has detected invalid state. Tell user
|
|
- * space.
|
|
- */
|
|
- return ret;
|
|
- }
|
|
-
|
|
- /*
|
|
- * We have no kernel internal state, i.e. no waiters in the
|
|
- * kernel. Waiters which are about to queue themselves are stuck
|
|
- * on hb->lock. So we can safely ignore them. We do neither
|
|
- * preserve the WAITERS bit not the OWNER_DIED one. We are the
|
|
- * owner.
|
|
- */
|
|
- if ((ret = cmpxchg_futex_value_locked(&curval, uaddr, uval, 0))) {
|
|
- spin_unlock(&hb->lock);
|
|
- switch (ret) {
|
|
- case -EFAULT:
|
|
- goto pi_faulted;
|
|
-
|
|
- case -EAGAIN:
|
|
- goto pi_retry;
|
|
-
|
|
- default:
|
|
- WARN_ON_ONCE(1);
|
|
- return ret;
|
|
- }
|
|
- }
|
|
-
|
|
- /*
|
|
- * If uval has changed, let user space handle it.
|
|
- */
|
|
- ret = (curval == uval) ? 0 : -EAGAIN;
|
|
-
|
|
-out_unlock:
|
|
- spin_unlock(&hb->lock);
|
|
- return ret;
|
|
-
|
|
-pi_retry:
|
|
- cond_resched();
|
|
- goto retry;
|
|
-
|
|
-pi_faulted:
|
|
-
|
|
- ret = fault_in_user_writeable(uaddr);
|
|
- if (!ret)
|
|
- goto retry;
|
|
-
|
|
- return ret;
|
|
-}
|
|
-
|
|
-/**
|
|
- * handle_early_requeue_pi_wakeup() - Handle early wakeup on the initial futex
|
|
- * @hb: the hash_bucket futex_q was original enqueued on
|
|
- * @q: the futex_q woken while waiting to be requeued
|
|
- * @timeout: the timeout associated with the wait (NULL if none)
|
|
- *
|
|
- * Determine the cause for the early wakeup.
|
|
- *
|
|
- * Return:
|
|
- * -EWOULDBLOCK or -ETIMEDOUT or -ERESTARTNOINTR
|
|
- */
|
|
-static inline
|
|
-int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
|
|
- struct futex_q *q,
|
|
- struct hrtimer_sleeper *timeout)
|
|
-{
|
|
- int ret;
|
|
-
|
|
- /*
|
|
- * With the hb lock held, we avoid races while we process the wakeup.
|
|
- * We only need to hold hb (and not hb2) to ensure atomicity as the
|
|
- * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb.
|
|
- * It can't be requeued from uaddr2 to something else since we don't
|
|
- * support a PI aware source futex for requeue.
|
|
- */
|
|
- WARN_ON_ONCE(&hb->lock != q->lock_ptr);
|
|
-
|
|
- /*
|
|
- * We were woken prior to requeue by a timeout or a signal.
|
|
- * Unqueue the futex_q and determine which it was.
|
|
- */
|
|
- plist_del(&q->list, &hb->chain);
|
|
- hb_waiters_dec(hb);
|
|
-
|
|
- /* Handle spurious wakeups gracefully */
|
|
- ret = -EWOULDBLOCK;
|
|
- if (timeout && !timeout->task)
|
|
- ret = -ETIMEDOUT;
|
|
- else if (signal_pending(current))
|
|
- ret = -ERESTARTNOINTR;
|
|
- return ret;
|
|
-}
|
|
-
|
|
-/**
|
|
- * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
|
|
- * @uaddr: the futex we initially wait on (non-pi)
|
|
- * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be
|
|
- * the same type, no requeueing from private to shared, etc.
|
|
- * @val: the expected value of uaddr
|
|
- * @abs_time: absolute timeout
|
|
- * @bitset: 32 bit wakeup bitset set by userspace, defaults to all
|
|
- * @uaddr2: the pi futex we will take prior to returning to user-space
|
|
- *
|
|
- * The caller will wait on uaddr and will be requeued by futex_requeue() to
|
|
- * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake
|
|
- * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to
|
|
- * userspace. This ensures the rt_mutex maintains an owner when it has waiters;
|
|
- * without one, the pi logic would not know which task to boost/deboost, if
|
|
- * there was a need to.
|
|
- *
|
|
- * We call schedule in futex_wait_queue_me() when we enqueue and return there
|
|
- * via the following--
|
|
- * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue()
|
|
- * 2) wakeup on uaddr2 after a requeue
|
|
- * 3) signal
|
|
- * 4) timeout
|
|
- *
|
|
- * If 3, cleanup and return -ERESTARTNOINTR.
|
|
- *
|
|
- * If 2, we may then block on trying to take the rt_mutex and return via:
|
|
- * 5) successful lock
|
|
- * 6) signal
|
|
- * 7) timeout
|
|
- * 8) other lock acquisition failure
|
|
- *
|
|
- * If 6, return -EWOULDBLOCK (restarting the syscall would do the same).
|
|
- *
|
|
- * If 4 or 7, we cleanup and return with -ETIMEDOUT.
|
|
- *
|
|
- * Return:
|
|
- * - 0 - On success;
|
|
- * - <0 - On error
|
|
- */
|
|
-static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
|
|
- u32 val, ktime_t *abs_time, u32 bitset,
|
|
- u32 __user *uaddr2)
|
|
-{
|
|
- struct hrtimer_sleeper timeout, *to;
|
|
- struct rt_mutex_waiter rt_waiter;
|
|
- struct futex_hash_bucket *hb;
|
|
- union futex_key key2 = FUTEX_KEY_INIT;
|
|
- struct futex_q q = futex_q_init;
|
|
- struct rt_mutex_base *pi_mutex;
|
|
- int res, ret;
|
|
-
|
|
- if (!IS_ENABLED(CONFIG_FUTEX_PI))
|
|
- return -ENOSYS;
|
|
-
|
|
- if (uaddr == uaddr2)
|
|
- return -EINVAL;
|
|
-
|
|
- if (!bitset)
|
|
- return -EINVAL;
|
|
-
|
|
- to = futex_setup_timer(abs_time, &timeout, flags,
|
|
- current->timer_slack_ns);
|
|
-
|
|
- /*
|
|
- * The waiter is allocated on our stack, manipulated by the requeue
|
|
- * code while we sleep on uaddr.
|
|
- */
|
|
- rt_mutex_init_waiter(&rt_waiter);
|
|
-
|
|
- ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, FUTEX_WRITE);
|
|
- if (unlikely(ret != 0))
|
|
- goto out;
|
|
-
|
|
- q.bitset = bitset;
|
|
- q.rt_waiter = &rt_waiter;
|
|
- q.requeue_pi_key = &key2;
|
|
-
|
|
- /*
|
|
- * Prepare to wait on uaddr. On success, it holds hb->lock and q
|
|
- * is initialized.
|
|
- */
|
|
- ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
|
|
- if (ret)
|
|
- goto out;
|
|
-
|
|
- /*
|
|
- * The check above which compares uaddrs is not sufficient for
|
|
- * shared futexes. We need to compare the keys:
|
|
- */
|
|
- if (match_futex(&q.key, &key2)) {
|
|
- queue_unlock(hb);
|
|
- ret = -EINVAL;
|
|
- goto out;
|
|
- }
|
|
-
|
|
- /* Queue the futex_q, drop the hb lock, wait for wakeup. */
|
|
- futex_wait_queue_me(hb, &q, to);
|
|
-
|
|
- switch (futex_requeue_pi_wakeup_sync(&q)) {
|
|
- case Q_REQUEUE_PI_IGNORE:
|
|
- /* The waiter is still on uaddr1 */
|
|
- spin_lock(&hb->lock);
|
|
- ret = handle_early_requeue_pi_wakeup(hb, &q, to);
|
|
- spin_unlock(&hb->lock);
|
|
- break;
|
|
-
|
|
- case Q_REQUEUE_PI_LOCKED:
|
|
- /* The requeue acquired the lock */
|
|
- if (q.pi_state && (q.pi_state->owner != current)) {
|
|
- spin_lock(q.lock_ptr);
|
|
- ret = fixup_owner(uaddr2, &q, true);
|
|
- /*
|
|
- * Drop the reference to the pi state which the
|
|
- * requeue_pi() code acquired for us.
|
|
- */
|
|
- put_pi_state(q.pi_state);
|
|
- spin_unlock(q.lock_ptr);
|
|
- /*
|
|
- * Adjust the return value. It's either -EFAULT or
|
|
- * success (1) but the caller expects 0 for success.
|
|
- */
|
|
- ret = ret < 0 ? ret : 0;
|
|
- }
|
|
- break;
|
|
-
|
|
- case Q_REQUEUE_PI_DONE:
|
|
- /* Requeue completed. Current is 'pi_blocked_on' the rtmutex */
|
|
- pi_mutex = &q.pi_state->pi_mutex;
|
|
- ret = rt_mutex_wait_proxy_lock(pi_mutex, to, &rt_waiter);
|
|
-
|
|
- /* Current is not longer pi_blocked_on */
|
|
- spin_lock(q.lock_ptr);
|
|
- if (ret && !rt_mutex_cleanup_proxy_lock(pi_mutex, &rt_waiter))
|
|
- ret = 0;
|
|
-
|
|
- debug_rt_mutex_free_waiter(&rt_waiter);
|
|
- /*
|
|
- * Fixup the pi_state owner and possibly acquire the lock if we
|
|
- * haven't already.
|
|
- */
|
|
- res = fixup_owner(uaddr2, &q, !ret);
|
|
- /*
|
|
- * If fixup_owner() returned an error, propagate that. If it
|
|
- * acquired the lock, clear -ETIMEDOUT or -EINTR.
|
|
- */
|
|
- if (res)
|
|
- ret = (res < 0) ? res : 0;
|
|
-
|
|
- unqueue_me_pi(&q);
|
|
- spin_unlock(q.lock_ptr);
|
|
-
|
|
- if (ret == -EINTR) {
|
|
- /*
|
|
- * We've already been requeued, but cannot restart
|
|
- * by calling futex_lock_pi() directly. We could
|
|
- * restart this syscall, but it would detect that
|
|
- * the user space "val" changed and return
|
|
- * -EWOULDBLOCK. Save the overhead of the restart
|
|
- * and return -EWOULDBLOCK directly.
|
|
- */
|
|
- ret = -EWOULDBLOCK;
|
|
- }
|
|
- break;
|
|
- default:
|
|
- BUG();
|
|
- }
|
|
-
|
|
-out:
|
|
- if (to) {
|
|
- hrtimer_cancel(&to->timer);
|
|
- destroy_hrtimer_on_stack(&to->timer);
|
|
- }
|
|
- return ret;
|
|
-}
|
|
-
|
|
-/*
|
|
- * Support for robust futexes: the kernel cleans up held futexes at
|
|
- * thread exit time.
|
|
- *
|
|
- * Implementation: user-space maintains a per-thread list of locks it
|
|
- * is holding. Upon do_exit(), the kernel carefully walks this list,
|
|
- * and marks all locks that are owned by this thread with the
|
|
- * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
|
|
- * always manipulated with the lock held, so the list is private and
|
|
- * per-thread. Userspace also maintains a per-thread 'list_op_pending'
|
|
- * field, to allow the kernel to clean up if the thread dies after
|
|
- * acquiring the lock, but just before it could have added itself to
|
|
- * the list. There can only be one such pending lock.
|
|
- */
|
|
-
|
|
-/**
|
|
- * sys_set_robust_list() - Set the robust-futex list head of a task
|
|
- * @head: pointer to the list-head
|
|
- * @len: length of the list-head, as userspace expects
|
|
- */
|
|
-SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
|
|
- size_t, len)
|
|
-{
|
|
- if (!futex_cmpxchg_enabled)
|
|
- return -ENOSYS;
|
|
- /*
|
|
- * The kernel knows only one size for now:
|
|
- */
|
|
- if (unlikely(len != sizeof(*head)))
|
|
- return -EINVAL;
|
|
-
|
|
- current->robust_list = head;
|
|
-
|
|
- return 0;
|
|
-}
|
|
-
|
|
-/**
|
|
- * sys_get_robust_list() - Get the robust-futex list head of a task
|
|
- * @pid: pid of the process [zero for current task]
|
|
- * @head_ptr: pointer to a list-head pointer, the kernel fills it in
|
|
- * @len_ptr: pointer to a length field, the kernel fills in the header size
|
|
- */
|
|
-SYSCALL_DEFINE3(get_robust_list, int, pid,
|
|
- struct robust_list_head __user * __user *, head_ptr,
|
|
- size_t __user *, len_ptr)
|
|
-{
|
|
- struct robust_list_head __user *head;
|
|
- unsigned long ret;
|
|
- struct task_struct *p;
|
|
-
|
|
- if (!futex_cmpxchg_enabled)
|
|
- return -ENOSYS;
|
|
-
|
|
- rcu_read_lock();
|
|
-
|
|
- ret = -ESRCH;
|
|
- if (!pid)
|
|
- p = current;
|
|
- else {
|
|
- p = find_task_by_vpid(pid);
|
|
- if (!p)
|
|
- goto err_unlock;
|
|
- }
|
|
-
|
|
- ret = -EPERM;
|
|
- if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
|
|
- goto err_unlock;
|
|
-
|
|
- head = p->robust_list;
|
|
- rcu_read_unlock();
|
|
-
|
|
- if (put_user(sizeof(*head), len_ptr))
|
|
- return -EFAULT;
|
|
- return put_user(head, head_ptr);
|
|
-
|
|
-err_unlock:
|
|
- rcu_read_unlock();
|
|
-
|
|
- return ret;
|
|
-}
|
|
-
|
|
-/* Constants for the pending_op argument of handle_futex_death */
|
|
-#define HANDLE_DEATH_PENDING true
|
|
-#define HANDLE_DEATH_LIST false
|
|
-
|
|
-/*
|
|
- * Process a futex-list entry, check whether it's owned by the
|
|
- * dying task, and do notification if so:
|
|
- */
|
|
-static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr,
|
|
- bool pi, bool pending_op)
|
|
-{
|
|
- u32 uval, nval, mval;
|
|
- int err;
|
|
-
|
|
- /* Futex address must be 32bit aligned */
|
|
- if ((((unsigned long)uaddr) % sizeof(*uaddr)) != 0)
|
|
- return -1;
|
|
-
|
|
-retry:
|
|
- if (get_user(uval, uaddr))
|
|
- return -1;
|
|
-
|
|
- /*
|
|
- * Special case for regular (non PI) futexes. The unlock path in
|
|
- * user space has two race scenarios:
|
|
- *
|
|
- * 1. The unlock path releases the user space futex value and
|
|
- * before it can execute the futex() syscall to wake up
|
|
- * waiters it is killed.
|
|
- *
|
|
- * 2. A woken up waiter is killed before it can acquire the
|
|
- * futex in user space.
|
|
- *
|
|
- * In both cases the TID validation below prevents a wakeup of
|
|
- * potential waiters which can cause these waiters to block
|
|
- * forever.
|
|
- *
|
|
- * In both cases the following conditions are met:
|
|
- *
|
|
- * 1) task->robust_list->list_op_pending != NULL
|
|
- * @pending_op == true
|
|
- * 2) User space futex value == 0
|
|
- * 3) Regular futex: @pi == false
|
|
- *
|
|
- * If these conditions are met, it is safe to attempt waking up a
|
|
- * potential waiter without touching the user space futex value and
|
|
- * trying to set the OWNER_DIED bit. The user space futex value is
|
|
- * uncontended and the rest of the user space mutex state is
|
|
- * consistent, so a woken waiter will just take over the
|
|
- * uncontended futex. Setting the OWNER_DIED bit would create
|
|
- * inconsistent state and malfunction of the user space owner died
|
|
- * handling.
|
|
- */
|
|
- if (pending_op && !pi && !uval) {
|
|
- futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
|
|
- return 0;
|
|
- }
|
|
-
|
|
- if ((uval & FUTEX_TID_MASK) != task_pid_vnr(curr))
|
|
- return 0;
|
|
-
|
|
- /*
|
|
- * Ok, this dying thread is truly holding a futex
|
|
- * of interest. Set the OWNER_DIED bit atomically
|
|
- * via cmpxchg, and if the value had FUTEX_WAITERS
|
|
- * set, wake up a waiter (if any). (We have to do a
|
|
- * futex_wake() even if OWNER_DIED is already set -
|
|
- * to handle the rare but possible case of recursive
|
|
- * thread-death.) The rest of the cleanup is done in
|
|
- * userspace.
|
|
- */
|
|
- mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
|
|
-
|
|
- /*
|
|
- * We are not holding a lock here, but we want to have
|
|
- * the pagefault_disable/enable() protection because
|
|
- * we want to handle the fault gracefully. If the
|
|
- * access fails we try to fault in the futex with R/W
|
|
- * verification via get_user_pages. get_user() above
|
|
- * does not guarantee R/W access. If that fails we
|
|
- * give up and leave the futex locked.
|
|
- */
|
|
- if ((err = cmpxchg_futex_value_locked(&nval, uaddr, uval, mval))) {
|
|
- switch (err) {
|
|
- case -EFAULT:
|
|
- if (fault_in_user_writeable(uaddr))
|
|
- return -1;
|
|
- goto retry;
|
|
-
|
|
- case -EAGAIN:
|
|
- cond_resched();
|
|
- goto retry;
|
|
-
|
|
- default:
|
|
- WARN_ON_ONCE(1);
|
|
- return err;
|
|
- }
|
|
- }
|
|
-
|
|
- if (nval != uval)
|
|
- goto retry;
|
|
-
|
|
- /*
|
|
- * Wake robust non-PI futexes here. The wakeup of
|
|
- * PI futexes happens in exit_pi_state():
|
|
- */
|
|
- if (!pi && (uval & FUTEX_WAITERS))
|
|
- futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
|
|
-
|
|
- return 0;
|
|
-}
|
|
-
|
|
-/*
|
|
- * Fetch a robust-list pointer. Bit 0 signals PI futexes:
|
|
- */
|
|
-static inline int fetch_robust_entry(struct robust_list __user **entry,
|
|
- struct robust_list __user * __user *head,
|
|
- unsigned int *pi)
|
|
-{
|
|
- unsigned long uentry;
|
|
-
|
|
- if (get_user(uentry, (unsigned long __user *)head))
|
|
- return -EFAULT;
|
|
-
|
|
- *entry = (void __user *)(uentry & ~1UL);
|
|
- *pi = uentry & 1;
|
|
-
|
|
- return 0;
|
|
-}
|
|
-
|
|
-/*
|
|
- * Walk curr->robust_list (very carefully, it's a userspace list!)
|
|
- * and mark any locks found there dead, and notify any waiters.
|
|
- *
|
|
- * We silently return on any sign of list-walking problem.
|
|
- */
|
|
-static void exit_robust_list(struct task_struct *curr)
|
|
-{
|
|
- struct robust_list_head __user *head = curr->robust_list;
|
|
- struct robust_list __user *entry, *next_entry, *pending;
|
|
- unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
|
|
- unsigned int next_pi;
|
|
- unsigned long futex_offset;
|
|
- int rc;
|
|
-
|
|
- if (!futex_cmpxchg_enabled)
|
|
- return;
|
|
-
|
|
- /*
|
|
- * Fetch the list head (which was registered earlier, via
|
|
- * sys_set_robust_list()):
|
|
- */
|
|
- if (fetch_robust_entry(&entry, &head->list.next, &pi))
|
|
- return;
|
|
- /*
|
|
- * Fetch the relative futex offset:
|
|
- */
|
|
- if (get_user(futex_offset, &head->futex_offset))
|
|
- return;
|
|
- /*
|
|
- * Fetch any possibly pending lock-add first, and handle it
|
|
- * if it exists:
|
|
- */
|
|
- if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
|
|
- return;
|
|
-
|
|
- next_entry = NULL; /* avoid warning with gcc */
|
|
- while (entry != &head->list) {
|
|
- /*
|
|
- * Fetch the next entry in the list before calling
|
|
- * handle_futex_death:
|
|
- */
|
|
- rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
|
|
- /*
|
|
- * A pending lock might already be on the list, so
|
|
- * don't process it twice:
|
|
- */
|
|
- if (entry != pending) {
|
|
- if (handle_futex_death((void __user *)entry + futex_offset,
|
|
- curr, pi, HANDLE_DEATH_LIST))
|
|
- return;
|
|
- }
|
|
- if (rc)
|
|
- return;
|
|
- entry = next_entry;
|
|
- pi = next_pi;
|
|
- /*
|
|
- * Avoid excessively long or circular lists:
|
|
- */
|
|
- if (!--limit)
|
|
- break;
|
|
-
|
|
- cond_resched();
|
|
- }
|
|
-
|
|
- if (pending) {
|
|
- handle_futex_death((void __user *)pending + futex_offset,
|
|
- curr, pip, HANDLE_DEATH_PENDING);
|
|
- }
|
|
-}
|
|
-
|
|
-static void futex_cleanup(struct task_struct *tsk)
|
|
-{
|
|
- if (unlikely(tsk->robust_list)) {
|
|
- exit_robust_list(tsk);
|
|
- tsk->robust_list = NULL;
|
|
- }
|
|
-
|
|
-#ifdef CONFIG_COMPAT
|
|
- if (unlikely(tsk->compat_robust_list)) {
|
|
- compat_exit_robust_list(tsk);
|
|
- tsk->compat_robust_list = NULL;
|
|
- }
|
|
-#endif
|
|
-
|
|
- if (unlikely(!list_empty(&tsk->pi_state_list)))
|
|
- exit_pi_state_list(tsk);
|
|
-}
|
|
-
|
|
-/**
|
|
- * futex_exit_recursive - Set the tasks futex state to FUTEX_STATE_DEAD
|
|
- * @tsk: task to set the state on
|
|
- *
|
|
- * Set the futex exit state of the task lockless. The futex waiter code
|
|
- * observes that state when a task is exiting and loops until the task has
|
|
- * actually finished the futex cleanup. The worst case for this is that the
|
|
- * waiter runs through the wait loop until the state becomes visible.
|
|
- *
|
|
- * This is called from the recursive fault handling path in do_exit().
|
|
- *
|
|
- * This is best effort. Either the futex exit code has run already or
|
|
- * not. If the OWNER_DIED bit has been set on the futex then the waiter can
|
|
- * take it over. If not, the problem is pushed back to user space. If the
|
|
- * futex exit code did not run yet, then an already queued waiter might
|
|
- * block forever, but there is nothing which can be done about that.
|
|
- */
|
|
-void futex_exit_recursive(struct task_struct *tsk)
|
|
-{
|
|
- /* If the state is FUTEX_STATE_EXITING then futex_exit_mutex is held */
|
|
- if (tsk->futex_state == FUTEX_STATE_EXITING)
|
|
- mutex_unlock(&tsk->futex_exit_mutex);
|
|
- tsk->futex_state = FUTEX_STATE_DEAD;
|
|
-}
|
|
-
|
|
-static void futex_cleanup_begin(struct task_struct *tsk)
|
|
-{
|
|
- /*
|
|
- * Prevent various race issues against a concurrent incoming waiter
|
|
- * including live locks by forcing the waiter to block on
|
|
- * tsk->futex_exit_mutex when it observes FUTEX_STATE_EXITING in
|
|
- * attach_to_pi_owner().
|
|
- */
|
|
- mutex_lock(&tsk->futex_exit_mutex);
|
|
-
|
|
- /*
|
|
- * Switch the state to FUTEX_STATE_EXITING under tsk->pi_lock.
|
|
- *
|
|
- * This ensures that all subsequent checks of tsk->futex_state in
|
|
- * attach_to_pi_owner() must observe FUTEX_STATE_EXITING with
|
|
- * tsk->pi_lock held.
|
|
- *
|
|
- * It guarantees also that a pi_state which was queued right before
|
|
- * the state change under tsk->pi_lock by a concurrent waiter must
|
|
- * be observed in exit_pi_state_list().
|
|
- */
|
|
- raw_spin_lock_irq(&tsk->pi_lock);
|
|
- tsk->futex_state = FUTEX_STATE_EXITING;
|
|
- raw_spin_unlock_irq(&tsk->pi_lock);
|
|
-}
|
|
-
|
|
-static void futex_cleanup_end(struct task_struct *tsk, int state)
|
|
-{
|
|
- /*
|
|
- * Lockless store. The only side effect is that an observer might
|
|
- * take another loop until it becomes visible.
|
|
- */
|
|
- tsk->futex_state = state;
|
|
- /*
|
|
- * Drop the exit protection. This unblocks waiters which observed
|
|
- * FUTEX_STATE_EXITING to reevaluate the state.
|
|
- */
|
|
- mutex_unlock(&tsk->futex_exit_mutex);
|
|
-}
|
|
-
|
|
-void futex_exec_release(struct task_struct *tsk)
|
|
-{
|
|
- /*
|
|
- * The state handling is done for consistency, but in the case of
|
|
- * exec() there is no way to prevent further damage as the PID stays
|
|
- * the same. But for the unlikely and arguably buggy case that a
|
|
- * futex is held on exec(), this provides at least as much state
|
|
- * consistency protection which is possible.
|
|
- */
|
|
- futex_cleanup_begin(tsk);
|
|
- futex_cleanup(tsk);
|
|
- /*
|
|
- * Reset the state to FUTEX_STATE_OK. The task is alive and about
|
|
- * exec a new binary.
|
|
- */
|
|
- futex_cleanup_end(tsk, FUTEX_STATE_OK);
|
|
-}
|
|
-
|
|
-void futex_exit_release(struct task_struct *tsk)
|
|
-{
|
|
- futex_cleanup_begin(tsk);
|
|
- futex_cleanup(tsk);
|
|
- futex_cleanup_end(tsk, FUTEX_STATE_DEAD);
|
|
-}
|
|
-
|
|
-long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
|
|
- u32 __user *uaddr2, u32 val2, u32 val3)
|
|
-{
|
|
- int cmd = op & FUTEX_CMD_MASK;
|
|
- unsigned int flags = 0;
|
|
-
|
|
- if (!(op & FUTEX_PRIVATE_FLAG))
|
|
- flags |= FLAGS_SHARED;
|
|
-
|
|
- if (op & FUTEX_CLOCK_REALTIME) {
|
|
- flags |= FLAGS_CLOCKRT;
|
|
- if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI &&
|
|
- cmd != FUTEX_LOCK_PI2)
|
|
- return -ENOSYS;
|
|
- }
|
|
-
|
|
- switch (cmd) {
|
|
- case FUTEX_LOCK_PI:
|
|
- case FUTEX_LOCK_PI2:
|
|
- case FUTEX_UNLOCK_PI:
|
|
- case FUTEX_TRYLOCK_PI:
|
|
- case FUTEX_WAIT_REQUEUE_PI:
|
|
- case FUTEX_CMP_REQUEUE_PI:
|
|
- if (!futex_cmpxchg_enabled)
|
|
- return -ENOSYS;
|
|
- }
|
|
-
|
|
- switch (cmd) {
|
|
- case FUTEX_WAIT:
|
|
- val3 = FUTEX_BITSET_MATCH_ANY;
|
|
- fallthrough;
|
|
- case FUTEX_WAIT_BITSET:
|
|
- return futex_wait(uaddr, flags, val, timeout, val3);
|
|
- case FUTEX_WAKE:
|
|
- val3 = FUTEX_BITSET_MATCH_ANY;
|
|
- fallthrough;
|
|
- case FUTEX_WAKE_BITSET:
|
|
- return futex_wake(uaddr, flags, val, val3);
|
|
- case FUTEX_REQUEUE:
|
|
- return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
|
|
- case FUTEX_CMP_REQUEUE:
|
|
- return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
|
|
- case FUTEX_WAKE_OP:
|
|
- return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
|
|
- case FUTEX_LOCK_PI:
|
|
- flags |= FLAGS_CLOCKRT;
|
|
- fallthrough;
|
|
- case FUTEX_LOCK_PI2:
|
|
- return futex_lock_pi(uaddr, flags, timeout, 0);
|
|
- case FUTEX_UNLOCK_PI:
|
|
- return futex_unlock_pi(uaddr, flags);
|
|
- case FUTEX_TRYLOCK_PI:
|
|
- return futex_lock_pi(uaddr, flags, NULL, 1);
|
|
- case FUTEX_WAIT_REQUEUE_PI:
|
|
- val3 = FUTEX_BITSET_MATCH_ANY;
|
|
- return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
|
|
- uaddr2);
|
|
- case FUTEX_CMP_REQUEUE_PI:
|
|
- return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
|
|
- }
|
|
- return -ENOSYS;
|
|
-}
|
|
-
|
|
-static __always_inline bool futex_cmd_has_timeout(u32 cmd)
|
|
-{
|
|
- switch (cmd) {
|
|
- case FUTEX_WAIT:
|
|
- case FUTEX_LOCK_PI:
|
|
- case FUTEX_LOCK_PI2:
|
|
- case FUTEX_WAIT_BITSET:
|
|
- case FUTEX_WAIT_REQUEUE_PI:
|
|
- return true;
|
|
- }
|
|
- return false;
|
|
-}
|
|
-
|
|
-static __always_inline int
|
|
-futex_init_timeout(u32 cmd, u32 op, struct timespec64 *ts, ktime_t *t)
|
|
-{
|
|
- if (!timespec64_valid(ts))
|
|
- return -EINVAL;
|
|
-
|
|
- *t = timespec64_to_ktime(*ts);
|
|
- if (cmd == FUTEX_WAIT)
|
|
- *t = ktime_add_safe(ktime_get(), *t);
|
|
- else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
|
|
- *t = timens_ktime_to_host(CLOCK_MONOTONIC, *t);
|
|
- return 0;
|
|
-}
|
|
-
|
|
-SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
|
|
- const struct __kernel_timespec __user *, utime,
|
|
- u32 __user *, uaddr2, u32, val3)
|
|
-{
|
|
- int ret, cmd = op & FUTEX_CMD_MASK;
|
|
- ktime_t t, *tp = NULL;
|
|
- struct timespec64 ts;
|
|
-
|
|
- if (utime && futex_cmd_has_timeout(cmd)) {
|
|
- if (unlikely(should_fail_futex(!(op & FUTEX_PRIVATE_FLAG))))
|
|
- return -EFAULT;
|
|
- if (get_timespec64(&ts, utime))
|
|
- return -EFAULT;
|
|
- ret = futex_init_timeout(cmd, op, &ts, &t);
|
|
- if (ret)
|
|
- return ret;
|
|
- tp = &t;
|
|
- }
|
|
-
|
|
- return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
|
|
-}
|
|
-
|
|
-#ifdef CONFIG_COMPAT
|
|
-/*
|
|
- * Fetch a robust-list pointer. Bit 0 signals PI futexes:
|
|
- */
|
|
-static inline int
|
|
-compat_fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
|
|
- compat_uptr_t __user *head, unsigned int *pi)
|
|
-{
|
|
- if (get_user(*uentry, head))
|
|
- return -EFAULT;
|
|
-
|
|
- *entry = compat_ptr((*uentry) & ~1);
|
|
- *pi = (unsigned int)(*uentry) & 1;
|
|
-
|
|
- return 0;
|
|
-}
|
|
-
|
|
-static void __user *futex_uaddr(struct robust_list __user *entry,
|
|
- compat_long_t futex_offset)
|
|
-{
|
|
- compat_uptr_t base = ptr_to_compat(entry);
|
|
- void __user *uaddr = compat_ptr(base + futex_offset);
|
|
-
|
|
- return uaddr;
|
|
-}
|
|
-
|
|
-/*
|
|
- * Walk curr->robust_list (very carefully, it's a userspace list!)
|
|
- * and mark any locks found there dead, and notify any waiters.
|
|
- *
|
|
- * We silently return on any sign of list-walking problem.
|
|
- */
|
|
-static void compat_exit_robust_list(struct task_struct *curr)
|
|
-{
|
|
- struct compat_robust_list_head __user *head = curr->compat_robust_list;
|
|
- struct robust_list __user *entry, *next_entry, *pending;
|
|
- unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
|
|
- unsigned int next_pi;
|
|
- compat_uptr_t uentry, next_uentry, upending;
|
|
- compat_long_t futex_offset;
|
|
- int rc;
|
|
-
|
|
- if (!futex_cmpxchg_enabled)
|
|
- return;
|
|
-
|
|
- /*
|
|
- * Fetch the list head (which was registered earlier, via
|
|
- * sys_set_robust_list()):
|
|
- */
|
|
- if (compat_fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
|
|
- return;
|
|
- /*
|
|
- * Fetch the relative futex offset:
|
|
- */
|
|
- if (get_user(futex_offset, &head->futex_offset))
|
|
- return;
|
|
- /*
|
|
- * Fetch any possibly pending lock-add first, and handle it
|
|
- * if it exists:
|
|
- */
|
|
- if (compat_fetch_robust_entry(&upending, &pending,
|
|
- &head->list_op_pending, &pip))
|
|
- return;
|
|
-
|
|
- next_entry = NULL; /* avoid warning with gcc */
|
|
- while (entry != (struct robust_list __user *) &head->list) {
|
|
- /*
|
|
- * Fetch the next entry in the list before calling
|
|
- * handle_futex_death:
|
|
- */
|
|
- rc = compat_fetch_robust_entry(&next_uentry, &next_entry,
|
|
- (compat_uptr_t __user *)&entry->next, &next_pi);
|
|
- /*
|
|
- * A pending lock might already be on the list, so
|
|
- * dont process it twice:
|
|
- */
|
|
- if (entry != pending) {
|
|
- void __user *uaddr = futex_uaddr(entry, futex_offset);
|
|
-
|
|
- if (handle_futex_death(uaddr, curr, pi,
|
|
- HANDLE_DEATH_LIST))
|
|
- return;
|
|
- }
|
|
- if (rc)
|
|
- return;
|
|
- uentry = next_uentry;
|
|
- entry = next_entry;
|
|
- pi = next_pi;
|
|
- /*
|
|
- * Avoid excessively long or circular lists:
|
|
- */
|
|
- if (!--limit)
|
|
- break;
|
|
-
|
|
- cond_resched();
|
|
- }
|
|
- if (pending) {
|
|
- void __user *uaddr = futex_uaddr(pending, futex_offset);
|
|
-
|
|
- handle_futex_death(uaddr, curr, pip, HANDLE_DEATH_PENDING);
|
|
- }
|
|
-}
|
|
-
|
|
-COMPAT_SYSCALL_DEFINE2(set_robust_list,
|
|
- struct compat_robust_list_head __user *, head,
|
|
- compat_size_t, len)
|
|
-{
|
|
- if (!futex_cmpxchg_enabled)
|
|
- return -ENOSYS;
|
|
-
|
|
- if (unlikely(len != sizeof(*head)))
|
|
- return -EINVAL;
|
|
-
|
|
- current->compat_robust_list = head;
|
|
-
|
|
- return 0;
|
|
-}
|
|
-
|
|
-COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
|
|
- compat_uptr_t __user *, head_ptr,
|
|
- compat_size_t __user *, len_ptr)
|
|
-{
|
|
- struct compat_robust_list_head __user *head;
|
|
- unsigned long ret;
|
|
- struct task_struct *p;
|
|
-
|
|
- if (!futex_cmpxchg_enabled)
|
|
- return -ENOSYS;
|
|
-
|
|
- rcu_read_lock();
|
|
-
|
|
- ret = -ESRCH;
|
|
- if (!pid)
|
|
- p = current;
|
|
- else {
|
|
- p = find_task_by_vpid(pid);
|
|
- if (!p)
|
|
- goto err_unlock;
|
|
- }
|
|
-
|
|
- ret = -EPERM;
|
|
- if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
|
|
- goto err_unlock;
|
|
-
|
|
- head = p->compat_robust_list;
|
|
- rcu_read_unlock();
|
|
-
|
|
- if (put_user(sizeof(*head), len_ptr))
|
|
- return -EFAULT;
|
|
- return put_user(ptr_to_compat(head), head_ptr);
|
|
-
|
|
-err_unlock:
|
|
- rcu_read_unlock();
|
|
-
|
|
- return ret;
|
|
-}
|
|
-#endif /* CONFIG_COMPAT */
|
|
-
|
|
-#ifdef CONFIG_COMPAT_32BIT_TIME
|
|
-SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,
|
|
- const struct old_timespec32 __user *, utime, u32 __user *, uaddr2,
|
|
- u32, val3)
|
|
-{
|
|
- int ret, cmd = op & FUTEX_CMD_MASK;
|
|
- ktime_t t, *tp = NULL;
|
|
- struct timespec64 ts;
|
|
-
|
|
- if (utime && futex_cmd_has_timeout(cmd)) {
|
|
- if (get_old_timespec32(&ts, utime))
|
|
- return -EFAULT;
|
|
- ret = futex_init_timeout(cmd, op, &ts, &t);
|
|
- if (ret)
|
|
- return ret;
|
|
- tp = &t;
|
|
- }
|
|
-
|
|
- return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
|
|
-}
|
|
-#endif /* CONFIG_COMPAT_32BIT_TIME */
|
|
-
|
|
-static void __init futex_detect_cmpxchg(void)
|
|
-{
|
|
-#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
|
|
- u32 curval;
|
|
-
|
|
- /*
|
|
- * This will fail and we want it. Some arch implementations do
|
|
- * runtime detection of the futex_atomic_cmpxchg_inatomic()
|
|
- * functionality. We want to know that before we call in any
|
|
- * of the complex code paths. Also we want to prevent
|
|
- * registration of robust lists in that case. NULL is
|
|
- * guaranteed to fault and we get -EFAULT on functional
|
|
- * implementation, the non-functional ones will return
|
|
- * -ENOSYS.
|
|
- */
|
|
- if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
|
|
- futex_cmpxchg_enabled = 1;
|
|
-#endif
|
|
-}
|
|
-
|
|
-static int __init futex_init(void)
|
|
-{
|
|
- unsigned int futex_shift;
|
|
- unsigned long i;
|
|
-
|
|
-#if CONFIG_BASE_SMALL
|
|
- futex_hashsize = 16;
|
|
-#else
|
|
- futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus());
|
|
-#endif
|
|
-
|
|
- futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues),
|
|
- futex_hashsize, 0,
|
|
- futex_hashsize < 256 ? HASH_SMALL : 0,
|
|
- &futex_shift, NULL,
|
|
- futex_hashsize, futex_hashsize);
|
|
- futex_hashsize = 1UL << futex_shift;
|
|
-
|
|
- futex_detect_cmpxchg();
|
|
-
|
|
- for (i = 0; i < futex_hashsize; i++) {
|
|
- atomic_set(&futex_queues[i].waiters, 0);
|
|
- plist_head_init(&futex_queues[i].chain);
|
|
- spin_lock_init(&futex_queues[i].lock);
|
|
- }
|
|
-
|
|
- return 0;
|
|
-}
|
|
-core_initcall(futex_init);
|
|
diff --git a/kernel/futex/Makefile b/kernel/futex/Makefile
|
|
new file mode 100644
|
|
index 000000000..b77188d1f
|
|
--- /dev/null
|
|
+++ b/kernel/futex/Makefile
|
|
@@ -0,0 +1,3 @@
|
|
+# SPDX-License-Identifier: GPL-2.0
|
|
+
|
|
+obj-y += core.o syscalls.o pi.o requeue.o waitwake.o
|
|
diff --git a/kernel/futex/core.c b/kernel/futex/core.c
|
|
new file mode 100644
|
|
index 000000000..25d8a88b3
|
|
--- /dev/null
|
|
+++ b/kernel/futex/core.c
|
|
@@ -0,0 +1,1176 @@
|
|
+// SPDX-License-Identifier: GPL-2.0-or-later
|
|
+/*
|
|
+ * Fast Userspace Mutexes (which I call "Futexes!").
|
|
+ * (C) Rusty Russell, IBM 2002
|
|
+ *
|
|
+ * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
|
|
+ * (C) Copyright 2003 Red Hat Inc, All Rights Reserved
|
|
+ *
|
|
+ * Removed page pinning, fix privately mapped COW pages and other cleanups
|
|
+ * (C) Copyright 2003, 2004 Jamie Lokier
|
|
+ *
|
|
+ * Robust futex support started by Ingo Molnar
|
|
+ * (C) Copyright 2006 Red Hat Inc, All Rights Reserved
|
|
+ * Thanks to Thomas Gleixner for suggestions, analysis and fixes.
|
|
+ *
|
|
+ * PI-futex support started by Ingo Molnar and Thomas Gleixner
|
|
+ * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
|
|
+ * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
|
|
+ *
|
|
+ * PRIVATE futexes by Eric Dumazet
|
|
+ * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
|
|
+ *
|
|
+ * Requeue-PI support by Darren Hart <dvhltc@us.ibm.com>
|
|
+ * Copyright (C) IBM Corporation, 2009
|
|
+ * Thanks to Thomas Gleixner for conceptual design and careful reviews.
|
|
+ *
|
|
+ * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
|
|
+ * enough at me, Linus for the original (flawed) idea, Matthew
|
|
+ * Kirkwood for proof-of-concept implementation.
|
|
+ *
|
|
+ * "The futexes are also cursed."
|
|
+ * "But they come in a choice of three flavours!"
|
|
+ */
|
|
+#include <linux/compat.h>
|
|
+#include <linux/jhash.h>
|
|
+#include <linux/pagemap.h>
|
|
+#include <linux/memblock.h>
|
|
+#include <linux/fault-inject.h>
|
|
+#include <linux/slab.h>
|
|
+
|
|
+#include "futex.h"
|
|
+#include "../locking/rtmutex_common.h"
|
|
+
|
|
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
|
|
+int __read_mostly futex_cmpxchg_enabled;
|
|
+#endif
|
|
+
|
|
+
|
|
+/*
|
|
+ * The base of the bucket array and its size are always used together
|
|
+ * (after initialization only in futex_hash()), so ensure that they
|
|
+ * reside in the same cacheline.
|
|
+ */
|
|
+static struct {
|
|
+ struct futex_hash_bucket *queues;
|
|
+ unsigned long hashsize;
|
|
+} __futex_data __read_mostly __aligned(2*sizeof(long));
|
|
+#define futex_queues (__futex_data.queues)
|
|
+#define futex_hashsize (__futex_data.hashsize)
|
|
+
|
|
+
|
|
+/*
|
|
+ * Fault injections for futexes.
|
|
+ */
|
|
+#ifdef CONFIG_FAIL_FUTEX
|
|
+
|
|
+static struct {
|
|
+ struct fault_attr attr;
|
|
+
|
|
+ bool ignore_private;
|
|
+} fail_futex = {
|
|
+ .attr = FAULT_ATTR_INITIALIZER,
|
|
+ .ignore_private = false,
|
|
+};
|
|
+
|
|
+static int __init setup_fail_futex(char *str)
|
|
+{
|
|
+ return setup_fault_attr(&fail_futex.attr, str);
|
|
+}
|
|
+__setup("fail_futex=", setup_fail_futex);
|
|
+
|
|
+bool should_fail_futex(bool fshared)
|
|
+{
|
|
+ if (fail_futex.ignore_private && !fshared)
|
|
+ return false;
|
|
+
|
|
+ return should_fail(&fail_futex.attr, 1);
|
|
+}
|
|
+
|
|
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
|
|
+
|
|
+static int __init fail_futex_debugfs(void)
|
|
+{
|
|
+ umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
|
|
+ struct dentry *dir;
|
|
+
|
|
+ dir = fault_create_debugfs_attr("fail_futex", NULL,
|
|
+ &fail_futex.attr);
|
|
+ if (IS_ERR(dir))
|
|
+ return PTR_ERR(dir);
|
|
+
|
|
+ debugfs_create_bool("ignore-private", mode, dir,
|
|
+ &fail_futex.ignore_private);
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+late_initcall(fail_futex_debugfs);
|
|
+
|
|
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
|
|
+
|
|
+#endif /* CONFIG_FAIL_FUTEX */
|
|
+
|
|
+/**
|
|
+ * futex_hash - Return the hash bucket in the global hash
|
|
+ * @key: Pointer to the futex key for which the hash is calculated
|
|
+ *
|
|
+ * We hash on the keys returned from get_futex_key (see below) and return the
|
|
+ * corresponding hash bucket in the global hash.
|
|
+ */
|
|
+struct futex_hash_bucket *futex_hash(union futex_key *key)
|
|
+{
|
|
+ u32 hash = jhash2((u32 *)key, offsetof(typeof(*key), both.offset) / 4,
|
|
+ key->both.offset);
|
|
+
|
|
+ return &futex_queues[hash & (futex_hashsize - 1)];
|
|
+}
|
|
+
|
|
+
|
|
+/**
|
|
+ * futex_setup_timer - set up the sleeping hrtimer.
|
|
+ * @time: ptr to the given timeout value
|
|
+ * @timeout: the hrtimer_sleeper structure to be set up
|
|
+ * @flags: futex flags
|
|
+ * @range_ns: optional range in ns
|
|
+ *
|
|
+ * Return: Initialized hrtimer_sleeper structure or NULL if no timeout
|
|
+ * value given
|
|
+ */
|
|
+struct hrtimer_sleeper *
|
|
+futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
|
|
+ int flags, u64 range_ns)
|
|
+{
|
|
+ if (!time)
|
|
+ return NULL;
|
|
+
|
|
+ hrtimer_init_sleeper_on_stack(timeout, (flags & FLAGS_CLOCKRT) ?
|
|
+ CLOCK_REALTIME : CLOCK_MONOTONIC,
|
|
+ HRTIMER_MODE_ABS);
|
|
+ /*
|
|
+ * If range_ns is 0, calling hrtimer_set_expires_range_ns() is
|
|
+ * effectively the same as calling hrtimer_set_expires().
|
|
+ */
|
|
+ hrtimer_set_expires_range_ns(&timeout->timer, *time, range_ns);
|
|
+
|
|
+ return timeout;
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Generate a machine wide unique identifier for this inode.
|
|
+ *
|
|
+ * This relies on u64 not wrapping in the life-time of the machine; which with
|
|
+ * 1ns resolution means almost 585 years.
|
|
+ *
|
|
+ * This further relies on the fact that a well formed program will not unmap
|
|
+ * the file while it has a (shared) futex waiting on it. This mapping will have
|
|
+ * a file reference which pins the mount and inode.
|
|
+ *
|
|
+ * If for some reason an inode gets evicted and read back in again, it will get
|
|
+ * a new sequence number and will _NOT_ match, even though it is the exact same
|
|
+ * file.
|
|
+ *
|
|
+ * It is important that futex_match() will never have a false-positive, esp.
|
|
+ * for PI futexes that can mess up the state. The above argues that false-negatives
|
|
+ * are only possible for malformed programs.
|
|
+ */
|
|
+static u64 get_inode_sequence_number(struct inode *inode)
|
|
+{
|
|
+ static atomic64_t i_seq;
|
|
+ u64 old;
|
|
+
|
|
+ /* Does the inode already have a sequence number? */
|
|
+ old = atomic64_read(&inode->i_sequence);
|
|
+ if (likely(old))
|
|
+ return old;
|
|
+
|
|
+ for (;;) {
|
|
+ u64 new = atomic64_add_return(1, &i_seq);
|
|
+ if (WARN_ON_ONCE(!new))
|
|
+ continue;
|
|
+
|
|
+ old = atomic64_cmpxchg_relaxed(&inode->i_sequence, 0, new);
|
|
+ if (old)
|
|
+ return old;
|
|
+ return new;
|
|
+ }
|
|
+}
|
|
+
|
|
+/**
|
|
+ * get_futex_key() - Get parameters which are the keys for a futex
|
|
+ * @uaddr: virtual address of the futex
|
|
+ * @fshared: false for a PROCESS_PRIVATE futex, true for PROCESS_SHARED
|
|
+ * @key: address where result is stored.
|
|
+ * @rw: mapping needs to be read/write (values: FUTEX_READ,
|
|
+ * FUTEX_WRITE)
|
|
+ *
|
|
+ * Return: a negative error code or 0
|
|
+ *
|
|
+ * The key words are stored in @key on success.
|
|
+ *
|
|
+ * For shared mappings (when @fshared), the key is:
|
|
+ *
|
|
+ * ( inode->i_sequence, page->index, offset_within_page )
|
|
+ *
|
|
+ * [ also see get_inode_sequence_number() ]
|
|
+ *
|
|
+ * For private mappings (or when !@fshared), the key is:
|
|
+ *
|
|
+ * ( current->mm, address, 0 )
|
|
+ *
|
|
+ * This allows (cross process, where applicable) identification of the futex
|
|
+ * without keeping the page pinned for the duration of the FUTEX_WAIT.
|
|
+ *
|
|
+ * lock_page() might sleep, the caller should not hold a spinlock.
|
|
+ */
|
|
+int get_futex_key(u32 __user *uaddr, bool fshared, union futex_key *key,
|
|
+ enum futex_access rw)
|
|
+{
|
|
+ unsigned long address = (unsigned long)uaddr;
|
|
+ struct mm_struct *mm = current->mm;
|
|
+ struct page *page, *tail;
|
|
+ struct address_space *mapping;
|
|
+ int err, ro = 0;
|
|
+
|
|
+ /*
|
|
+ * The futex address must be "naturally" aligned.
|
|
+ */
|
|
+ key->both.offset = address % PAGE_SIZE;
|
|
+ if (unlikely((address % sizeof(u32)) != 0))
|
|
+ return -EINVAL;
|
|
+ address -= key->both.offset;
|
|
+
|
|
+ if (unlikely(!access_ok(uaddr, sizeof(u32))))
|
|
+ return -EFAULT;
|
|
+
|
|
+ if (unlikely(should_fail_futex(fshared)))
|
|
+ return -EFAULT;
|
|
+
|
|
+ /*
|
|
+ * PROCESS_PRIVATE futexes are fast.
|
|
+ * As the mm cannot disappear under us and the 'key' only needs
|
|
+ * virtual address, we dont even have to find the underlying vma.
|
|
+ * Note : We do have to check 'uaddr' is a valid user address,
|
|
+ * but access_ok() should be faster than find_vma()
|
|
+ */
|
|
+ if (!fshared) {
|
|
+ key->private.mm = mm;
|
|
+ key->private.address = address;
|
|
+ return 0;
|
|
+ }
|
|
+
|
|
+again:
|
|
+ /* Ignore any VERIFY_READ mapping (futex common case) */
|
|
+ if (unlikely(should_fail_futex(true)))
|
|
+ return -EFAULT;
|
|
+
|
|
+ err = get_user_pages_fast(address, 1, FOLL_WRITE, &page);
|
|
+ /*
|
|
+ * If write access is not required (eg. FUTEX_WAIT), try
|
|
+ * and get read-only access.
|
|
+ */
|
|
+ if (err == -EFAULT && rw == FUTEX_READ) {
|
|
+ err = get_user_pages_fast(address, 1, 0, &page);
|
|
+ ro = 1;
|
|
+ }
|
|
+ if (err < 0)
|
|
+ return err;
|
|
+ else
|
|
+ err = 0;
|
|
+
|
|
+ /*
|
|
+ * The treatment of mapping from this point on is critical. The page
|
|
+ * lock protects many things but in this context the page lock
|
|
+ * stabilizes mapping, prevents inode freeing in the shared
|
|
+ * file-backed region case and guards against movement to swap cache.
|
|
+ *
|
|
+ * Strictly speaking the page lock is not needed in all cases being
|
|
+ * considered here and page lock forces unnecessarily serialization
|
|
+ * From this point on, mapping will be re-verified if necessary and
|
|
+ * page lock will be acquired only if it is unavoidable
|
|
+ *
|
|
+ * Mapping checks require the head page for any compound page so the
|
|
+ * head page and mapping is looked up now. For anonymous pages, it
|
|
+ * does not matter if the page splits in the future as the key is
|
|
+ * based on the address. For filesystem-backed pages, the tail is
|
|
+ * required as the index of the page determines the key. For
|
|
+ * base pages, there is no tail page and tail == page.
|
|
+ */
|
|
+ tail = page;
|
|
+ page = compound_head(page);
|
|
+ mapping = READ_ONCE(page->mapping);
|
|
+
|
|
+ /*
|
|
+ * If page->mapping is NULL, then it cannot be a PageAnon
|
|
+ * page; but it might be the ZERO_PAGE or in the gate area or
|
|
+ * in a special mapping (all cases which we are happy to fail);
|
|
+ * or it may have been a good file page when get_user_pages_fast
|
|
+ * found it, but truncated or holepunched or subjected to
|
|
+ * invalidate_complete_page2 before we got the page lock (also
|
|
+ * cases which we are happy to fail). And we hold a reference,
|
|
+ * so refcount care in invalidate_complete_page's remove_mapping
|
|
+ * prevents drop_caches from setting mapping to NULL beneath us.
|
|
+ *
|
|
+ * The case we do have to guard against is when memory pressure made
|
|
+ * shmem_writepage move it from filecache to swapcache beneath us:
|
|
+ * an unlikely race, but we do need to retry for page->mapping.
|
|
+ */
|
|
+ if (unlikely(!mapping)) {
|
|
+ int shmem_swizzled;
|
|
+
|
|
+ /*
|
|
+ * Page lock is required to identify which special case above
|
|
+ * applies. If this is really a shmem page then the page lock
|
|
+ * will prevent unexpected transitions.
|
|
+ */
|
|
+ lock_page(page);
|
|
+ shmem_swizzled = PageSwapCache(page) || page->mapping;
|
|
+ unlock_page(page);
|
|
+ put_page(page);
|
|
+
|
|
+ if (shmem_swizzled)
|
|
+ goto again;
|
|
+
|
|
+ return -EFAULT;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * Private mappings are handled in a simple way.
|
|
+ *
|
|
+ * If the futex key is stored on an anonymous page, then the associated
|
|
+ * object is the mm which is implicitly pinned by the calling process.
|
|
+ *
|
|
+ * NOTE: When userspace waits on a MAP_SHARED mapping, even if
|
|
+ * it's a read-only handle, it's expected that futexes attach to
|
|
+ * the object not the particular process.
|
|
+ */
|
|
+ if (PageAnon(page)) {
|
|
+ /*
|
|
+ * A RO anonymous page will never change and thus doesn't make
|
|
+ * sense for futex operations.
|
|
+ */
|
|
+ if (unlikely(should_fail_futex(true)) || ro) {
|
|
+ err = -EFAULT;
|
|
+ goto out;
|
|
+ }
|
|
+
|
|
+ key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
|
|
+ key->private.mm = mm;
|
|
+ key->private.address = address;
|
|
+
|
|
+ } else {
|
|
+ struct inode *inode;
|
|
+
|
|
+ /*
|
|
+ * The associated futex object in this case is the inode and
|
|
+ * the page->mapping must be traversed. Ordinarily this should
|
|
+ * be stabilised under page lock but it's not strictly
|
|
+ * necessary in this case as we just want to pin the inode, not
|
|
+ * update the radix tree or anything like that.
|
|
+ *
|
|
+ * The RCU read lock is taken as the inode is finally freed
|
|
+ * under RCU. If the mapping still matches expectations then the
|
|
+ * mapping->host can be safely accessed as being a valid inode.
|
|
+ */
|
|
+ rcu_read_lock();
|
|
+
|
|
+ if (READ_ONCE(page->mapping) != mapping) {
|
|
+ rcu_read_unlock();
|
|
+ put_page(page);
|
|
+
|
|
+ goto again;
|
|
+ }
|
|
+
|
|
+ inode = READ_ONCE(mapping->host);
|
|
+ if (!inode) {
|
|
+ rcu_read_unlock();
|
|
+ put_page(page);
|
|
+
|
|
+ goto again;
|
|
+ }
|
|
+
|
|
+ key->both.offset |= FUT_OFF_INODE; /* inode-based key */
|
|
+ key->shared.i_seq = get_inode_sequence_number(inode);
|
|
+ key->shared.pgoff = page_to_pgoff(tail);
|
|
+ rcu_read_unlock();
|
|
+ }
|
|
+
|
|
+out:
|
|
+ put_page(page);
|
|
+ return err;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * fault_in_user_writeable() - Fault in user address and verify RW access
|
|
+ * @uaddr: pointer to faulting user space address
|
|
+ *
|
|
+ * Slow path to fixup the fault we just took in the atomic write
|
|
+ * access to @uaddr.
|
|
+ *
|
|
+ * We have no generic implementation of a non-destructive write to the
|
|
+ * user address. We know that we faulted in the atomic pagefault
|
|
+ * disabled section so we can as well avoid the #PF overhead by
|
|
+ * calling get_user_pages() right away.
|
|
+ */
|
|
+int fault_in_user_writeable(u32 __user *uaddr)
|
|
+{
|
|
+ struct mm_struct *mm = current->mm;
|
|
+ int ret;
|
|
+
|
|
+ mmap_read_lock(mm);
|
|
+ ret = fixup_user_fault(mm, (unsigned long)uaddr,
|
|
+ FAULT_FLAG_WRITE, NULL);
|
|
+ mmap_read_unlock(mm);
|
|
+
|
|
+ return ret < 0 ? ret : 0;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_top_waiter() - Return the highest priority waiter on a futex
|
|
+ * @hb: the hash bucket the futex_q's reside in
|
|
+ * @key: the futex key (to distinguish it from other futex futex_q's)
|
|
+ *
|
|
+ * Must be called with the hb lock held.
|
|
+ */
|
|
+struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, union futex_key *key)
|
|
+{
|
|
+ struct futex_q *this;
|
|
+
|
|
+ plist_for_each_entry(this, &hb->chain, list) {
|
|
+ if (futex_match(&this->key, key))
|
|
+ return this;
|
|
+ }
|
|
+ return NULL;
|
|
+}
|
|
+
|
|
+int futex_cmpxchg_value_locked(u32 *curval, u32 __user *uaddr, u32 uval, u32 newval)
|
|
+{
|
|
+ int ret;
|
|
+
|
|
+ pagefault_disable();
|
|
+ ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval);
|
|
+ pagefault_enable();
|
|
+
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+int futex_get_value_locked(u32 *dest, u32 __user *from)
|
|
+{
|
|
+ int ret;
|
|
+
|
|
+ pagefault_disable();
|
|
+ ret = __get_user(*dest, from);
|
|
+ pagefault_enable();
|
|
+
|
|
+ return ret ? -EFAULT : 0;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * wait_for_owner_exiting - Block until the owner has exited
|
|
+ * @ret: owner's current futex lock status
|
|
+ * @exiting: Pointer to the exiting task
|
|
+ *
|
|
+ * Caller must hold a refcount on @exiting.
|
|
+ */
|
|
+void wait_for_owner_exiting(int ret, struct task_struct *exiting)
|
|
+{
|
|
+ if (ret != -EBUSY) {
|
|
+ WARN_ON_ONCE(exiting);
|
|
+ return;
|
|
+ }
|
|
+
|
|
+ if (WARN_ON_ONCE(ret == -EBUSY && !exiting))
|
|
+ return;
|
|
+
|
|
+ mutex_lock(&exiting->futex_exit_mutex);
|
|
+ /*
|
|
+ * No point in doing state checking here. If the waiter got here
|
|
+ * while the task was in exec()->exec_futex_release() then it can
|
|
+ * have any FUTEX_STATE_* value when the waiter has acquired the
|
|
+ * mutex. OK, if running, EXITING or DEAD if it reached exit()
|
|
+ * already. Highly unlikely and not a problem. Just one more round
|
|
+ * through the futex maze.
|
|
+ */
|
|
+ mutex_unlock(&exiting->futex_exit_mutex);
|
|
+
|
|
+ put_task_struct(exiting);
|
|
+}
|
|
+
|
|
+/**
|
|
+ * __futex_unqueue() - Remove the futex_q from its futex_hash_bucket
|
|
+ * @q: The futex_q to unqueue
|
|
+ *
|
|
+ * The q->lock_ptr must not be NULL and must be held by the caller.
|
|
+ */
|
|
+void __futex_unqueue(struct futex_q *q)
|
|
+{
|
|
+ struct futex_hash_bucket *hb;
|
|
+
|
|
+ if (WARN_ON_SMP(!q->lock_ptr) || WARN_ON(plist_node_empty(&q->list)))
|
|
+ return;
|
|
+ lockdep_assert_held(q->lock_ptr);
|
|
+
|
|
+ hb = container_of(q->lock_ptr, struct futex_hash_bucket, lock);
|
|
+ plist_del(&q->list, &hb->chain);
|
|
+ futex_hb_waiters_dec(hb);
|
|
+}
|
|
+
|
|
+/* The key must be already stored in q->key. */
|
|
+struct futex_hash_bucket *futex_q_lock(struct futex_q *q)
|
|
+ __acquires(&hb->lock)
|
|
+{
|
|
+ struct futex_hash_bucket *hb;
|
|
+
|
|
+ hb = futex_hash(&q->key);
|
|
+
|
|
+ /*
|
|
+ * Increment the counter before taking the lock so that
|
|
+ * a potential waker won't miss a to-be-slept task that is
|
|
+ * waiting for the spinlock. This is safe as all futex_q_lock()
|
|
+ * users end up calling futex_queue(). Similarly, for housekeeping,
|
|
+ * decrement the counter at futex_q_unlock() when some error has
|
|
+ * occurred and we don't end up adding the task to the list.
|
|
+ */
|
|
+ futex_hb_waiters_inc(hb); /* implies smp_mb(); (A) */
|
|
+
|
|
+ q->lock_ptr = &hb->lock;
|
|
+
|
|
+ spin_lock(&hb->lock);
|
|
+ return hb;
|
|
+}
|
|
+
|
|
+void futex_q_unlock(struct futex_hash_bucket *hb)
|
|
+ __releases(&hb->lock)
|
|
+{
|
|
+ spin_unlock(&hb->lock);
|
|
+ futex_hb_waiters_dec(hb);
|
|
+}
|
|
+
|
|
+void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb)
|
|
+{
|
|
+ int prio;
|
|
+
|
|
+ /*
|
|
+ * The priority used to register this element is
|
|
+ * - either the real thread-priority for the real-time threads
|
|
+ * (i.e. threads with a priority lower than MAX_RT_PRIO)
|
|
+ * - or MAX_RT_PRIO for non-RT threads.
|
|
+ * Thus, all RT-threads are woken first in priority order, and
|
|
+ * the others are woken last, in FIFO order.
|
|
+ */
|
|
+ prio = min(current->normal_prio, MAX_RT_PRIO);
|
|
+
|
|
+ plist_node_init(&q->list, prio);
|
|
+ plist_add(&q->list, &hb->chain);
|
|
+ q->task = current;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_unqueue() - Remove the futex_q from its futex_hash_bucket
|
|
+ * @q: The futex_q to unqueue
|
|
+ *
|
|
+ * The q->lock_ptr must not be held by the caller. A call to futex_unqueue() must
|
|
+ * be paired with exactly one earlier call to futex_queue().
|
|
+ *
|
|
+ * Return:
|
|
+ * - 1 - if the futex_q was still queued (and we removed unqueued it);
|
|
+ * - 0 - if the futex_q was already removed by the waking thread
|
|
+ */
|
|
+int futex_unqueue(struct futex_q *q)
|
|
+{
|
|
+ spinlock_t *lock_ptr;
|
|
+ int ret = 0;
|
|
+
|
|
+ /* In the common case we don't take the spinlock, which is nice. */
|
|
+retry:
|
|
+ /*
|
|
+ * q->lock_ptr can change between this read and the following spin_lock.
|
|
+ * Use READ_ONCE to forbid the compiler from reloading q->lock_ptr and
|
|
+ * optimizing lock_ptr out of the logic below.
|
|
+ */
|
|
+ lock_ptr = READ_ONCE(q->lock_ptr);
|
|
+ if (lock_ptr != NULL) {
|
|
+ spin_lock(lock_ptr);
|
|
+ /*
|
|
+ * q->lock_ptr can change between reading it and
|
|
+ * spin_lock(), causing us to take the wrong lock. This
|
|
+ * corrects the race condition.
|
|
+ *
|
|
+ * Reasoning goes like this: if we have the wrong lock,
|
|
+ * q->lock_ptr must have changed (maybe several times)
|
|
+ * between reading it and the spin_lock(). It can
|
|
+ * change again after the spin_lock() but only if it was
|
|
+ * already changed before the spin_lock(). It cannot,
|
|
+ * however, change back to the original value. Therefore
|
|
+ * we can detect whether we acquired the correct lock.
|
|
+ */
|
|
+ if (unlikely(lock_ptr != q->lock_ptr)) {
|
|
+ spin_unlock(lock_ptr);
|
|
+ goto retry;
|
|
+ }
|
|
+ __futex_unqueue(q);
|
|
+
|
|
+ BUG_ON(q->pi_state);
|
|
+
|
|
+ spin_unlock(lock_ptr);
|
|
+ ret = 1;
|
|
+ }
|
|
+
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+/*
|
|
+ * PI futexes can not be requeued and must remove themselves from the
|
|
+ * hash bucket. The hash bucket lock (i.e. lock_ptr) is held.
|
|
+ */
|
|
+void futex_unqueue_pi(struct futex_q *q)
|
|
+{
|
|
+ __futex_unqueue(q);
|
|
+
|
|
+ BUG_ON(!q->pi_state);
|
|
+ put_pi_state(q->pi_state);
|
|
+ q->pi_state = NULL;
|
|
+}
|
|
+
|
|
+/* Constants for the pending_op argument of handle_futex_death */
|
|
+#define HANDLE_DEATH_PENDING true
|
|
+#define HANDLE_DEATH_LIST false
|
|
+
|
|
+/*
|
|
+ * Process a futex-list entry, check whether it's owned by the
|
|
+ * dying task, and do notification if so:
|
|
+ */
|
|
+static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr,
|
|
+ bool pi, bool pending_op)
|
|
+{
|
|
+ u32 uval, nval, mval;
|
|
+ int err;
|
|
+
|
|
+ /* Futex address must be 32bit aligned */
|
|
+ if ((((unsigned long)uaddr) % sizeof(*uaddr)) != 0)
|
|
+ return -1;
|
|
+
|
|
+retry:
|
|
+ if (get_user(uval, uaddr))
|
|
+ return -1;
|
|
+
|
|
+ /*
|
|
+ * Special case for regular (non PI) futexes. The unlock path in
|
|
+ * user space has two race scenarios:
|
|
+ *
|
|
+ * 1. The unlock path releases the user space futex value and
|
|
+ * before it can execute the futex() syscall to wake up
|
|
+ * waiters it is killed.
|
|
+ *
|
|
+ * 2. A woken up waiter is killed before it can acquire the
|
|
+ * futex in user space.
|
|
+ *
|
|
+ * In both cases the TID validation below prevents a wakeup of
|
|
+ * potential waiters which can cause these waiters to block
|
|
+ * forever.
|
|
+ *
|
|
+ * In both cases the following conditions are met:
|
|
+ *
|
|
+ * 1) task->robust_list->list_op_pending != NULL
|
|
+ * @pending_op == true
|
|
+ * 2) User space futex value == 0
|
|
+ * 3) Regular futex: @pi == false
|
|
+ *
|
|
+ * If these conditions are met, it is safe to attempt waking up a
|
|
+ * potential waiter without touching the user space futex value and
|
|
+ * trying to set the OWNER_DIED bit. The user space futex value is
|
|
+ * uncontended and the rest of the user space mutex state is
|
|
+ * consistent, so a woken waiter will just take over the
|
|
+ * uncontended futex. Setting the OWNER_DIED bit would create
|
|
+ * inconsistent state and malfunction of the user space owner died
|
|
+ * handling.
|
|
+ */
|
|
+ if (pending_op && !pi && !uval) {
|
|
+ futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
|
|
+ return 0;
|
|
+ }
|
|
+
|
|
+ if ((uval & FUTEX_TID_MASK) != task_pid_vnr(curr))
|
|
+ return 0;
|
|
+
|
|
+ /*
|
|
+ * Ok, this dying thread is truly holding a futex
|
|
+ * of interest. Set the OWNER_DIED bit atomically
|
|
+ * via cmpxchg, and if the value had FUTEX_WAITERS
|
|
+ * set, wake up a waiter (if any). (We have to do a
|
|
+ * futex_wake() even if OWNER_DIED is already set -
|
|
+ * to handle the rare but possible case of recursive
|
|
+ * thread-death.) The rest of the cleanup is done in
|
|
+ * userspace.
|
|
+ */
|
|
+ mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
|
|
+
|
|
+ /*
|
|
+ * We are not holding a lock here, but we want to have
|
|
+ * the pagefault_disable/enable() protection because
|
|
+ * we want to handle the fault gracefully. If the
|
|
+ * access fails we try to fault in the futex with R/W
|
|
+ * verification via get_user_pages. get_user() above
|
|
+ * does not guarantee R/W access. If that fails we
|
|
+ * give up and leave the futex locked.
|
|
+ */
|
|
+ if ((err = futex_cmpxchg_value_locked(&nval, uaddr, uval, mval))) {
|
|
+ switch (err) {
|
|
+ case -EFAULT:
|
|
+ if (fault_in_user_writeable(uaddr))
|
|
+ return -1;
|
|
+ goto retry;
|
|
+
|
|
+ case -EAGAIN:
|
|
+ cond_resched();
|
|
+ goto retry;
|
|
+
|
|
+ default:
|
|
+ WARN_ON_ONCE(1);
|
|
+ return err;
|
|
+ }
|
|
+ }
|
|
+
|
|
+ if (nval != uval)
|
|
+ goto retry;
|
|
+
|
|
+ /*
|
|
+ * Wake robust non-PI futexes here. The wakeup of
|
|
+ * PI futexes happens in exit_pi_state():
|
|
+ */
|
|
+ if (!pi && (uval & FUTEX_WAITERS))
|
|
+ futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Fetch a robust-list pointer. Bit 0 signals PI futexes:
|
|
+ */
|
|
+static inline int fetch_robust_entry(struct robust_list __user **entry,
|
|
+ struct robust_list __user * __user *head,
|
|
+ unsigned int *pi)
|
|
+{
|
|
+ unsigned long uentry;
|
|
+
|
|
+ if (get_user(uentry, (unsigned long __user *)head))
|
|
+ return -EFAULT;
|
|
+
|
|
+ *entry = (void __user *)(uentry & ~1UL);
|
|
+ *pi = uentry & 1;
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Walk curr->robust_list (very carefully, it's a userspace list!)
|
|
+ * and mark any locks found there dead, and notify any waiters.
|
|
+ *
|
|
+ * We silently return on any sign of list-walking problem.
|
|
+ */
|
|
+static void exit_robust_list(struct task_struct *curr)
|
|
+{
|
|
+ struct robust_list_head __user *head = curr->robust_list;
|
|
+ struct robust_list __user *entry, *next_entry, *pending;
|
|
+ unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
|
|
+ unsigned int next_pi;
|
|
+ unsigned long futex_offset;
|
|
+ int rc;
|
|
+
|
|
+ if (!futex_cmpxchg_enabled)
|
|
+ return;
|
|
+
|
|
+ /*
|
|
+ * Fetch the list head (which was registered earlier, via
|
|
+ * sys_set_robust_list()):
|
|
+ */
|
|
+ if (fetch_robust_entry(&entry, &head->list.next, &pi))
|
|
+ return;
|
|
+ /*
|
|
+ * Fetch the relative futex offset:
|
|
+ */
|
|
+ if (get_user(futex_offset, &head->futex_offset))
|
|
+ return;
|
|
+ /*
|
|
+ * Fetch any possibly pending lock-add first, and handle it
|
|
+ * if it exists:
|
|
+ */
|
|
+ if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
|
|
+ return;
|
|
+
|
|
+ next_entry = NULL; /* avoid warning with gcc */
|
|
+ while (entry != &head->list) {
|
|
+ /*
|
|
+ * Fetch the next entry in the list before calling
|
|
+ * handle_futex_death:
|
|
+ */
|
|
+ rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
|
|
+ /*
|
|
+ * A pending lock might already be on the list, so
|
|
+ * don't process it twice:
|
|
+ */
|
|
+ if (entry != pending) {
|
|
+ if (handle_futex_death((void __user *)entry + futex_offset,
|
|
+ curr, pi, HANDLE_DEATH_LIST))
|
|
+ return;
|
|
+ }
|
|
+ if (rc)
|
|
+ return;
|
|
+ entry = next_entry;
|
|
+ pi = next_pi;
|
|
+ /*
|
|
+ * Avoid excessively long or circular lists:
|
|
+ */
|
|
+ if (!--limit)
|
|
+ break;
|
|
+
|
|
+ cond_resched();
|
|
+ }
|
|
+
|
|
+ if (pending) {
|
|
+ handle_futex_death((void __user *)pending + futex_offset,
|
|
+ curr, pip, HANDLE_DEATH_PENDING);
|
|
+ }
|
|
+}
|
|
+
|
|
+#ifdef CONFIG_COMPAT
|
|
+static void __user *futex_uaddr(struct robust_list __user *entry,
|
|
+ compat_long_t futex_offset)
|
|
+{
|
|
+ compat_uptr_t base = ptr_to_compat(entry);
|
|
+ void __user *uaddr = compat_ptr(base + futex_offset);
|
|
+
|
|
+ return uaddr;
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Fetch a robust-list pointer. Bit 0 signals PI futexes:
|
|
+ */
|
|
+static inline int
|
|
+compat_fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
|
|
+ compat_uptr_t __user *head, unsigned int *pi)
|
|
+{
|
|
+ if (get_user(*uentry, head))
|
|
+ return -EFAULT;
|
|
+
|
|
+ *entry = compat_ptr((*uentry) & ~1);
|
|
+ *pi = (unsigned int)(*uentry) & 1;
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Walk curr->robust_list (very carefully, it's a userspace list!)
|
|
+ * and mark any locks found there dead, and notify any waiters.
|
|
+ *
|
|
+ * We silently return on any sign of list-walking problem.
|
|
+ */
|
|
+static void compat_exit_robust_list(struct task_struct *curr)
|
|
+{
|
|
+ struct compat_robust_list_head __user *head = curr->compat_robust_list;
|
|
+ struct robust_list __user *entry, *next_entry, *pending;
|
|
+ unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
|
|
+ unsigned int next_pi;
|
|
+ compat_uptr_t uentry, next_uentry, upending;
|
|
+ compat_long_t futex_offset;
|
|
+ int rc;
|
|
+
|
|
+ if (!futex_cmpxchg_enabled)
|
|
+ return;
|
|
+
|
|
+ /*
|
|
+ * Fetch the list head (which was registered earlier, via
|
|
+ * sys_set_robust_list()):
|
|
+ */
|
|
+ if (compat_fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
|
|
+ return;
|
|
+ /*
|
|
+ * Fetch the relative futex offset:
|
|
+ */
|
|
+ if (get_user(futex_offset, &head->futex_offset))
|
|
+ return;
|
|
+ /*
|
|
+ * Fetch any possibly pending lock-add first, and handle it
|
|
+ * if it exists:
|
|
+ */
|
|
+ if (compat_fetch_robust_entry(&upending, &pending,
|
|
+ &head->list_op_pending, &pip))
|
|
+ return;
|
|
+
|
|
+ next_entry = NULL; /* avoid warning with gcc */
|
|
+ while (entry != (struct robust_list __user *) &head->list) {
|
|
+ /*
|
|
+ * Fetch the next entry in the list before calling
|
|
+ * handle_futex_death:
|
|
+ */
|
|
+ rc = compat_fetch_robust_entry(&next_uentry, &next_entry,
|
|
+ (compat_uptr_t __user *)&entry->next, &next_pi);
|
|
+ /*
|
|
+ * A pending lock might already be on the list, so
|
|
+ * dont process it twice:
|
|
+ */
|
|
+ if (entry != pending) {
|
|
+ void __user *uaddr = futex_uaddr(entry, futex_offset);
|
|
+
|
|
+ if (handle_futex_death(uaddr, curr, pi,
|
|
+ HANDLE_DEATH_LIST))
|
|
+ return;
|
|
+ }
|
|
+ if (rc)
|
|
+ return;
|
|
+ uentry = next_uentry;
|
|
+ entry = next_entry;
|
|
+ pi = next_pi;
|
|
+ /*
|
|
+ * Avoid excessively long or circular lists:
|
|
+ */
|
|
+ if (!--limit)
|
|
+ break;
|
|
+
|
|
+ cond_resched();
|
|
+ }
|
|
+ if (pending) {
|
|
+ void __user *uaddr = futex_uaddr(pending, futex_offset);
|
|
+
|
|
+ handle_futex_death(uaddr, curr, pip, HANDLE_DEATH_PENDING);
|
|
+ }
|
|
+}
|
|
+#endif
|
|
+
|
|
+#ifdef CONFIG_FUTEX_PI
|
|
+
|
|
+/*
|
|
+ * This task is holding PI mutexes at exit time => bad.
|
|
+ * Kernel cleans up PI-state, but userspace is likely hosed.
|
|
+ * (Robust-futex cleanup is separate and might save the day for userspace.)
|
|
+ */
|
|
+static void exit_pi_state_list(struct task_struct *curr)
|
|
+{
|
|
+ struct list_head *next, *head = &curr->pi_state_list;
|
|
+ struct futex_pi_state *pi_state;
|
|
+ struct futex_hash_bucket *hb;
|
|
+ union futex_key key = FUTEX_KEY_INIT;
|
|
+
|
|
+ if (!futex_cmpxchg_enabled)
|
|
+ return;
|
|
+ /*
|
|
+ * We are a ZOMBIE and nobody can enqueue itself on
|
|
+ * pi_state_list anymore, but we have to be careful
|
|
+ * versus waiters unqueueing themselves:
|
|
+ */
|
|
+ raw_spin_lock_irq(&curr->pi_lock);
|
|
+ while (!list_empty(head)) {
|
|
+ next = head->next;
|
|
+ pi_state = list_entry(next, struct futex_pi_state, list);
|
|
+ key = pi_state->key;
|
|
+ hb = futex_hash(&key);
|
|
+
|
|
+ /*
|
|
+ * We can race against put_pi_state() removing itself from the
|
|
+ * list (a waiter going away). put_pi_state() will first
|
|
+ * decrement the reference count and then modify the list, so
|
|
+ * its possible to see the list entry but fail this reference
|
|
+ * acquire.
|
|
+ *
|
|
+ * In that case; drop the locks to let put_pi_state() make
|
|
+ * progress and retry the loop.
|
|
+ */
|
|
+ if (!refcount_inc_not_zero(&pi_state->refcount)) {
|
|
+ raw_spin_unlock_irq(&curr->pi_lock);
|
|
+ cpu_relax();
|
|
+ raw_spin_lock_irq(&curr->pi_lock);
|
|
+ continue;
|
|
+ }
|
|
+ raw_spin_unlock_irq(&curr->pi_lock);
|
|
+
|
|
+ spin_lock(&hb->lock);
|
|
+ raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+ raw_spin_lock(&curr->pi_lock);
|
|
+ /*
|
|
+ * We dropped the pi-lock, so re-check whether this
|
|
+ * task still owns the PI-state:
|
|
+ */
|
|
+ if (head->next != next) {
|
|
+ /* retain curr->pi_lock for the loop invariant */
|
|
+ raw_spin_unlock(&pi_state->pi_mutex.wait_lock);
|
|
+ spin_unlock(&hb->lock);
|
|
+ put_pi_state(pi_state);
|
|
+ continue;
|
|
+ }
|
|
+
|
|
+ WARN_ON(pi_state->owner != curr);
|
|
+ WARN_ON(list_empty(&pi_state->list));
|
|
+ list_del_init(&pi_state->list);
|
|
+ pi_state->owner = NULL;
|
|
+
|
|
+ raw_spin_unlock(&curr->pi_lock);
|
|
+ raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+ spin_unlock(&hb->lock);
|
|
+
|
|
+ rt_mutex_futex_unlock(&pi_state->pi_mutex);
|
|
+ put_pi_state(pi_state);
|
|
+
|
|
+ raw_spin_lock_irq(&curr->pi_lock);
|
|
+ }
|
|
+ raw_spin_unlock_irq(&curr->pi_lock);
|
|
+}
|
|
+#else
|
|
+static inline void exit_pi_state_list(struct task_struct *curr) { }
|
|
+#endif
|
|
+
|
|
+static void futex_cleanup(struct task_struct *tsk)
|
|
+{
|
|
+ if (unlikely(tsk->robust_list)) {
|
|
+ exit_robust_list(tsk);
|
|
+ tsk->robust_list = NULL;
|
|
+ }
|
|
+
|
|
+#ifdef CONFIG_COMPAT
|
|
+ if (unlikely(tsk->compat_robust_list)) {
|
|
+ compat_exit_robust_list(tsk);
|
|
+ tsk->compat_robust_list = NULL;
|
|
+ }
|
|
+#endif
|
|
+
|
|
+ if (unlikely(!list_empty(&tsk->pi_state_list)))
|
|
+ exit_pi_state_list(tsk);
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_exit_recursive - Set the tasks futex state to FUTEX_STATE_DEAD
|
|
+ * @tsk: task to set the state on
|
|
+ *
|
|
+ * Set the futex exit state of the task lockless. The futex waiter code
|
|
+ * observes that state when a task is exiting and loops until the task has
|
|
+ * actually finished the futex cleanup. The worst case for this is that the
|
|
+ * waiter runs through the wait loop until the state becomes visible.
|
|
+ *
|
|
+ * This is called from the recursive fault handling path in do_exit().
|
|
+ *
|
|
+ * This is best effort. Either the futex exit code has run already or
|
|
+ * not. If the OWNER_DIED bit has been set on the futex then the waiter can
|
|
+ * take it over. If not, the problem is pushed back to user space. If the
|
|
+ * futex exit code did not run yet, then an already queued waiter might
|
|
+ * block forever, but there is nothing which can be done about that.
|
|
+ */
|
|
+void futex_exit_recursive(struct task_struct *tsk)
|
|
+{
|
|
+ /* If the state is FUTEX_STATE_EXITING then futex_exit_mutex is held */
|
|
+ if (tsk->futex_state == FUTEX_STATE_EXITING)
|
|
+ mutex_unlock(&tsk->futex_exit_mutex);
|
|
+ tsk->futex_state = FUTEX_STATE_DEAD;
|
|
+}
|
|
+
|
|
+static void futex_cleanup_begin(struct task_struct *tsk)
|
|
+{
|
|
+ /*
|
|
+ * Prevent various race issues against a concurrent incoming waiter
|
|
+ * including live locks by forcing the waiter to block on
|
|
+ * tsk->futex_exit_mutex when it observes FUTEX_STATE_EXITING in
|
|
+ * attach_to_pi_owner().
|
|
+ */
|
|
+ mutex_lock(&tsk->futex_exit_mutex);
|
|
+
|
|
+ /*
|
|
+ * Switch the state to FUTEX_STATE_EXITING under tsk->pi_lock.
|
|
+ *
|
|
+ * This ensures that all subsequent checks of tsk->futex_state in
|
|
+ * attach_to_pi_owner() must observe FUTEX_STATE_EXITING with
|
|
+ * tsk->pi_lock held.
|
|
+ *
|
|
+ * It guarantees also that a pi_state which was queued right before
|
|
+ * the state change under tsk->pi_lock by a concurrent waiter must
|
|
+ * be observed in exit_pi_state_list().
|
|
+ */
|
|
+ raw_spin_lock_irq(&tsk->pi_lock);
|
|
+ tsk->futex_state = FUTEX_STATE_EXITING;
|
|
+ raw_spin_unlock_irq(&tsk->pi_lock);
|
|
+}
|
|
+
|
|
+static void futex_cleanup_end(struct task_struct *tsk, int state)
|
|
+{
|
|
+ /*
|
|
+ * Lockless store. The only side effect is that an observer might
|
|
+ * take another loop until it becomes visible.
|
|
+ */
|
|
+ tsk->futex_state = state;
|
|
+ /*
|
|
+ * Drop the exit protection. This unblocks waiters which observed
|
|
+ * FUTEX_STATE_EXITING to reevaluate the state.
|
|
+ */
|
|
+ mutex_unlock(&tsk->futex_exit_mutex);
|
|
+}
|
|
+
|
|
+void futex_exec_release(struct task_struct *tsk)
|
|
+{
|
|
+ /*
|
|
+ * The state handling is done for consistency, but in the case of
|
|
+ * exec() there is no way to prevent further damage as the PID stays
|
|
+ * the same. But for the unlikely and arguably buggy case that a
|
|
+ * futex is held on exec(), this provides at least as much state
|
|
+ * consistency protection which is possible.
|
|
+ */
|
|
+ futex_cleanup_begin(tsk);
|
|
+ futex_cleanup(tsk);
|
|
+ /*
|
|
+ * Reset the state to FUTEX_STATE_OK. The task is alive and about
|
|
+ * exec a new binary.
|
|
+ */
|
|
+ futex_cleanup_end(tsk, FUTEX_STATE_OK);
|
|
+}
|
|
+
|
|
+void futex_exit_release(struct task_struct *tsk)
|
|
+{
|
|
+ futex_cleanup_begin(tsk);
|
|
+ futex_cleanup(tsk);
|
|
+ futex_cleanup_end(tsk, FUTEX_STATE_DEAD);
|
|
+}
|
|
+
|
|
+static void __init futex_detect_cmpxchg(void)
|
|
+{
|
|
+#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
|
|
+ u32 curval;
|
|
+
|
|
+ /*
|
|
+ * This will fail and we want it. Some arch implementations do
|
|
+ * runtime detection of the futex_atomic_cmpxchg_inatomic()
|
|
+ * functionality. We want to know that before we call in any
|
|
+ * of the complex code paths. Also we want to prevent
|
|
+ * registration of robust lists in that case. NULL is
|
|
+ * guaranteed to fault and we get -EFAULT on functional
|
|
+ * implementation, the non-functional ones will return
|
|
+ * -ENOSYS.
|
|
+ */
|
|
+ if (futex_cmpxchg_value_locked(&curval, NULL, 0, 0) == -EFAULT)
|
|
+ futex_cmpxchg_enabled = 1;
|
|
+#endif
|
|
+}
|
|
+
|
|
+static int __init futex_init(void)
|
|
+{
|
|
+ unsigned int futex_shift;
|
|
+ unsigned long i;
|
|
+
|
|
+#if CONFIG_BASE_SMALL
|
|
+ futex_hashsize = 16;
|
|
+#else
|
|
+ futex_hashsize = roundup_pow_of_two(256 * num_possible_cpus());
|
|
+#endif
|
|
+
|
|
+ futex_queues = alloc_large_system_hash("futex", sizeof(*futex_queues),
|
|
+ futex_hashsize, 0,
|
|
+ futex_hashsize < 256 ? HASH_SMALL : 0,
|
|
+ &futex_shift, NULL,
|
|
+ futex_hashsize, futex_hashsize);
|
|
+ futex_hashsize = 1UL << futex_shift;
|
|
+
|
|
+ futex_detect_cmpxchg();
|
|
+
|
|
+ for (i = 0; i < futex_hashsize; i++) {
|
|
+ atomic_set(&futex_queues[i].waiters, 0);
|
|
+ plist_head_init(&futex_queues[i].chain);
|
|
+ spin_lock_init(&futex_queues[i].lock);
|
|
+ }
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+core_initcall(futex_init);
|
|
diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
|
|
new file mode 100644
|
|
index 000000000..948fcf317
|
|
--- /dev/null
|
|
+++ b/kernel/futex/futex.h
|
|
@@ -0,0 +1,295 @@
|
|
+/* SPDX-License-Identifier: GPL-2.0 */
|
|
+#ifndef _FUTEX_H
|
|
+#define _FUTEX_H
|
|
+
|
|
+#include <linux/futex.h>
|
|
+#include <linux/sched/wake_q.h>
|
|
+
|
|
+#include <asm/futex.h>
|
|
+
|
|
+/*
|
|
+ * Futex flags used to encode options to functions and preserve them across
|
|
+ * restarts.
|
|
+ */
|
|
+#ifdef CONFIG_MMU
|
|
+# define FLAGS_SHARED 0x01
|
|
+#else
|
|
+/*
|
|
+ * NOMMU does not have per process address space. Let the compiler optimize
|
|
+ * code away.
|
|
+ */
|
|
+# define FLAGS_SHARED 0x00
|
|
+#endif
|
|
+#define FLAGS_CLOCKRT 0x02
|
|
+#define FLAGS_HAS_TIMEOUT 0x04
|
|
+
|
|
+#ifdef CONFIG_HAVE_FUTEX_CMPXCHG
|
|
+#define futex_cmpxchg_enabled 1
|
|
+#else
|
|
+extern int __read_mostly futex_cmpxchg_enabled;
|
|
+#endif
|
|
+
|
|
+#ifdef CONFIG_FAIL_FUTEX
|
|
+extern bool should_fail_futex(bool fshared);
|
|
+#else
|
|
+static inline bool should_fail_futex(bool fshared)
|
|
+{
|
|
+ return false;
|
|
+}
|
|
+#endif
|
|
+
|
|
+/*
|
|
+ * Hash buckets are shared by all the futex_keys that hash to the same
|
|
+ * location. Each key may have multiple futex_q structures, one for each task
|
|
+ * waiting on a futex.
|
|
+ */
|
|
+struct futex_hash_bucket {
|
|
+ atomic_t waiters;
|
|
+ spinlock_t lock;
|
|
+ struct plist_head chain;
|
|
+} ____cacheline_aligned_in_smp;
|
|
+
|
|
+/*
|
|
+ * Priority Inheritance state:
|
|
+ */
|
|
+struct futex_pi_state {
|
|
+ /*
|
|
+ * list of 'owned' pi_state instances - these have to be
|
|
+ * cleaned up in do_exit() if the task exits prematurely:
|
|
+ */
|
|
+ struct list_head list;
|
|
+
|
|
+ /*
|
|
+ * The PI object:
|
|
+ */
|
|
+ struct rt_mutex_base pi_mutex;
|
|
+
|
|
+ struct task_struct *owner;
|
|
+ refcount_t refcount;
|
|
+
|
|
+ union futex_key key;
|
|
+} __randomize_layout;
|
|
+
|
|
+/**
|
|
+ * struct futex_q - The hashed futex queue entry, one per waiting task
|
|
+ * @list: priority-sorted list of tasks waiting on this futex
|
|
+ * @task: the task waiting on the futex
|
|
+ * @lock_ptr: the hash bucket lock
|
|
+ * @key: the key the futex is hashed on
|
|
+ * @pi_state: optional priority inheritance state
|
|
+ * @rt_waiter: rt_waiter storage for use with requeue_pi
|
|
+ * @requeue_pi_key: the requeue_pi target futex key
|
|
+ * @bitset: bitset for the optional bitmasked wakeup
|
|
+ * @requeue_state: State field for futex_requeue_pi()
|
|
+ * @requeue_wait: RCU wait for futex_requeue_pi() (RT only)
|
|
+ *
|
|
+ * We use this hashed waitqueue, instead of a normal wait_queue_entry_t, so
|
|
+ * we can wake only the relevant ones (hashed queues may be shared).
|
|
+ *
|
|
+ * A futex_q has a woken state, just like tasks have TASK_RUNNING.
|
|
+ * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
|
|
+ * The order of wakeup is always to make the first condition true, then
|
|
+ * the second.
|
|
+ *
|
|
+ * PI futexes are typically woken before they are removed from the hash list via
|
|
+ * the rt_mutex code. See futex_unqueue_pi().
|
|
+ */
|
|
+struct futex_q {
|
|
+ struct plist_node list;
|
|
+
|
|
+ struct task_struct *task;
|
|
+ spinlock_t *lock_ptr;
|
|
+ union futex_key key;
|
|
+ struct futex_pi_state *pi_state;
|
|
+ struct rt_mutex_waiter *rt_waiter;
|
|
+ union futex_key *requeue_pi_key;
|
|
+ u32 bitset;
|
|
+ atomic_t requeue_state;
|
|
+#ifdef CONFIG_PREEMPT_RT
|
|
+ struct rcuwait requeue_wait;
|
|
+#endif
|
|
+} __randomize_layout;
|
|
+
|
|
+extern const struct futex_q futex_q_init;
|
|
+
|
|
+enum futex_access {
|
|
+ FUTEX_READ,
|
|
+ FUTEX_WRITE
|
|
+};
|
|
+
|
|
+extern int get_futex_key(u32 __user *uaddr, bool fshared, union futex_key *key,
|
|
+ enum futex_access rw);
|
|
+
|
|
+extern struct hrtimer_sleeper *
|
|
+futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
|
|
+ int flags, u64 range_ns);
|
|
+
|
|
+extern struct futex_hash_bucket *futex_hash(union futex_key *key);
|
|
+
|
|
+/**
|
|
+ * futex_match - Check whether two futex keys are equal
|
|
+ * @key1: Pointer to key1
|
|
+ * @key2: Pointer to key2
|
|
+ *
|
|
+ * Return 1 if two futex_keys are equal, 0 otherwise.
|
|
+ */
|
|
+static inline int futex_match(union futex_key *key1, union futex_key *key2)
|
|
+{
|
|
+ return (key1 && key2
|
|
+ && key1->both.word == key2->both.word
|
|
+ && key1->both.ptr == key2->both.ptr
|
|
+ && key1->both.offset == key2->both.offset);
|
|
+}
|
|
+
|
|
+extern int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
|
|
+ struct futex_q *q, struct futex_hash_bucket **hb);
|
|
+extern void futex_wait_queue(struct futex_hash_bucket *hb, struct futex_q *q,
|
|
+ struct hrtimer_sleeper *timeout);
|
|
+extern void futex_wake_mark(struct wake_q_head *wake_q, struct futex_q *q);
|
|
+
|
|
+extern int fault_in_user_writeable(u32 __user *uaddr);
|
|
+extern int futex_cmpxchg_value_locked(u32 *curval, u32 __user *uaddr, u32 uval, u32 newval);
|
|
+extern int futex_get_value_locked(u32 *dest, u32 __user *from);
|
|
+extern struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb, union futex_key *key);
|
|
+
|
|
+extern void __futex_unqueue(struct futex_q *q);
|
|
+extern void __futex_queue(struct futex_q *q, struct futex_hash_bucket *hb);
|
|
+extern int futex_unqueue(struct futex_q *q);
|
|
+
|
|
+/**
|
|
+ * futex_queue() - Enqueue the futex_q on the futex_hash_bucket
|
|
+ * @q: The futex_q to enqueue
|
|
+ * @hb: The destination hash bucket
|
|
+ *
|
|
+ * The hb->lock must be held by the caller, and is released here. A call to
|
|
+ * futex_queue() is typically paired with exactly one call to futex_unqueue(). The
|
|
+ * exceptions involve the PI related operations, which may use futex_unqueue_pi()
|
|
+ * or nothing if the unqueue is done as part of the wake process and the unqueue
|
|
+ * state is implicit in the state of woken task (see futex_wait_requeue_pi() for
|
|
+ * an example).
|
|
+ */
|
|
+static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb)
|
|
+ __releases(&hb->lock)
|
|
+{
|
|
+ __futex_queue(q, hb);
|
|
+ spin_unlock(&hb->lock);
|
|
+}
|
|
+
|
|
+extern void futex_unqueue_pi(struct futex_q *q);
|
|
+
|
|
+extern void wait_for_owner_exiting(int ret, struct task_struct *exiting);
|
|
+
|
|
+/*
|
|
+ * Reflects a new waiter being added to the waitqueue.
|
|
+ */
|
|
+static inline void futex_hb_waiters_inc(struct futex_hash_bucket *hb)
|
|
+{
|
|
+#ifdef CONFIG_SMP
|
|
+ atomic_inc(&hb->waiters);
|
|
+ /*
|
|
+ * Full barrier (A), see the ordering comment above.
|
|
+ */
|
|
+ smp_mb__after_atomic();
|
|
+#endif
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Reflects a waiter being removed from the waitqueue by wakeup
|
|
+ * paths.
|
|
+ */
|
|
+static inline void futex_hb_waiters_dec(struct futex_hash_bucket *hb)
|
|
+{
|
|
+#ifdef CONFIG_SMP
|
|
+ atomic_dec(&hb->waiters);
|
|
+#endif
|
|
+}
|
|
+
|
|
+static inline int futex_hb_waiters_pending(struct futex_hash_bucket *hb)
|
|
+{
|
|
+#ifdef CONFIG_SMP
|
|
+ /*
|
|
+ * Full barrier (B), see the ordering comment above.
|
|
+ */
|
|
+ smp_mb();
|
|
+ return atomic_read(&hb->waiters);
|
|
+#else
|
|
+ return 1;
|
|
+#endif
|
|
+}
|
|
+
|
|
+extern struct futex_hash_bucket *futex_q_lock(struct futex_q *q);
|
|
+extern void futex_q_unlock(struct futex_hash_bucket *hb);
|
|
+
|
|
+
|
|
+extern int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
|
|
+ union futex_key *key,
|
|
+ struct futex_pi_state **ps,
|
|
+ struct task_struct *task,
|
|
+ struct task_struct **exiting,
|
|
+ int set_waiters);
|
|
+
|
|
+extern int refill_pi_state_cache(void);
|
|
+extern void get_pi_state(struct futex_pi_state *pi_state);
|
|
+extern void put_pi_state(struct futex_pi_state *pi_state);
|
|
+extern int fixup_pi_owner(u32 __user *uaddr, struct futex_q *q, int locked);
|
|
+
|
|
+/*
|
|
+ * Express the locking dependencies for lockdep:
|
|
+ */
|
|
+static inline void
|
|
+double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
|
|
+{
|
|
+ if (hb1 > hb2)
|
|
+ swap(hb1, hb2);
|
|
+
|
|
+ spin_lock(&hb1->lock);
|
|
+ if (hb1 != hb2)
|
|
+ spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
|
|
+}
|
|
+
|
|
+static inline void
|
|
+double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
|
|
+{
|
|
+ spin_unlock(&hb1->lock);
|
|
+ if (hb1 != hb2)
|
|
+ spin_unlock(&hb2->lock);
|
|
+}
|
|
+
|
|
+/* syscalls */
|
|
+
|
|
+extern int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, u32
|
|
+ val, ktime_t *abs_time, u32 bitset, u32 __user
|
|
+ *uaddr2);
|
|
+
|
|
+extern int futex_requeue(u32 __user *uaddr1, unsigned int flags,
|
|
+ u32 __user *uaddr2, int nr_wake, int nr_requeue,
|
|
+ u32 *cmpval, int requeue_pi);
|
|
+
|
|
+extern int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val,
|
|
+ ktime_t *abs_time, u32 bitset);
|
|
+
|
|
+/**
|
|
+ * struct futex_vector - Auxiliary struct for futex_waitv()
|
|
+ * @w: Userspace provided data
|
|
+ * @q: Kernel side data
|
|
+ *
|
|
+ * Struct used to build an array with all data need for futex_waitv()
|
|
+ */
|
|
+struct futex_vector {
|
|
+ struct futex_waitv w;
|
|
+ struct futex_q q;
|
|
+};
|
|
+
|
|
+extern int futex_wait_multiple(struct futex_vector *vs, unsigned int count,
|
|
+ struct hrtimer_sleeper *to);
|
|
+
|
|
+extern int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset);
|
|
+
|
|
+extern int futex_wake_op(u32 __user *uaddr1, unsigned int flags,
|
|
+ u32 __user *uaddr2, int nr_wake, int nr_wake2, int op);
|
|
+
|
|
+extern int futex_unlock_pi(u32 __user *uaddr, unsigned int flags);
|
|
+
|
|
+extern int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int trylock);
|
|
+
|
|
+#endif /* _FUTEX_H */
|
|
diff --git a/kernel/futex/pi.c b/kernel/futex/pi.c
|
|
new file mode 100644
|
|
index 000000000..183b28c32
|
|
--- /dev/null
|
|
+++ b/kernel/futex/pi.c
|
|
@@ -0,0 +1,1233 @@
|
|
+// SPDX-License-Identifier: GPL-2.0-or-later
|
|
+
|
|
+#include <linux/slab.h>
|
|
+#include <linux/sched/task.h>
|
|
+
|
|
+#include "futex.h"
|
|
+#include "../locking/rtmutex_common.h"
|
|
+
|
|
+/*
|
|
+ * PI code:
|
|
+ */
|
|
+int refill_pi_state_cache(void)
|
|
+{
|
|
+ struct futex_pi_state *pi_state;
|
|
+
|
|
+ if (likely(current->pi_state_cache))
|
|
+ return 0;
|
|
+
|
|
+ pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
|
|
+
|
|
+ if (!pi_state)
|
|
+ return -ENOMEM;
|
|
+
|
|
+ INIT_LIST_HEAD(&pi_state->list);
|
|
+ /* pi_mutex gets initialized later */
|
|
+ pi_state->owner = NULL;
|
|
+ refcount_set(&pi_state->refcount, 1);
|
|
+ pi_state->key = FUTEX_KEY_INIT;
|
|
+
|
|
+ current->pi_state_cache = pi_state;
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+static struct futex_pi_state *alloc_pi_state(void)
|
|
+{
|
|
+ struct futex_pi_state *pi_state = current->pi_state_cache;
|
|
+
|
|
+ WARN_ON(!pi_state);
|
|
+ current->pi_state_cache = NULL;
|
|
+
|
|
+ return pi_state;
|
|
+}
|
|
+
|
|
+static void pi_state_update_owner(struct futex_pi_state *pi_state,
|
|
+ struct task_struct *new_owner)
|
|
+{
|
|
+ struct task_struct *old_owner = pi_state->owner;
|
|
+
|
|
+ lockdep_assert_held(&pi_state->pi_mutex.wait_lock);
|
|
+
|
|
+ if (old_owner) {
|
|
+ raw_spin_lock(&old_owner->pi_lock);
|
|
+ WARN_ON(list_empty(&pi_state->list));
|
|
+ list_del_init(&pi_state->list);
|
|
+ raw_spin_unlock(&old_owner->pi_lock);
|
|
+ }
|
|
+
|
|
+ if (new_owner) {
|
|
+ raw_spin_lock(&new_owner->pi_lock);
|
|
+ WARN_ON(!list_empty(&pi_state->list));
|
|
+ list_add(&pi_state->list, &new_owner->pi_state_list);
|
|
+ pi_state->owner = new_owner;
|
|
+ raw_spin_unlock(&new_owner->pi_lock);
|
|
+ }
|
|
+}
|
|
+
|
|
+void get_pi_state(struct futex_pi_state *pi_state)
|
|
+{
|
|
+ WARN_ON_ONCE(!refcount_inc_not_zero(&pi_state->refcount));
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Drops a reference to the pi_state object and frees or caches it
|
|
+ * when the last reference is gone.
|
|
+ */
|
|
+void put_pi_state(struct futex_pi_state *pi_state)
|
|
+{
|
|
+ if (!pi_state)
|
|
+ return;
|
|
+
|
|
+ if (!refcount_dec_and_test(&pi_state->refcount))
|
|
+ return;
|
|
+
|
|
+ /*
|
|
+ * If pi_state->owner is NULL, the owner is most probably dying
|
|
+ * and has cleaned up the pi_state already
|
|
+ */
|
|
+ if (pi_state->owner) {
|
|
+ unsigned long flags;
|
|
+
|
|
+ raw_spin_lock_irqsave(&pi_state->pi_mutex.wait_lock, flags);
|
|
+ pi_state_update_owner(pi_state, NULL);
|
|
+ rt_mutex_proxy_unlock(&pi_state->pi_mutex);
|
|
+ raw_spin_unlock_irqrestore(&pi_state->pi_mutex.wait_lock, flags);
|
|
+ }
|
|
+
|
|
+ if (current->pi_state_cache) {
|
|
+ kfree(pi_state);
|
|
+ } else {
|
|
+ /*
|
|
+ * pi_state->list is already empty.
|
|
+ * clear pi_state->owner.
|
|
+ * refcount is at 0 - put it back to 1.
|
|
+ */
|
|
+ pi_state->owner = NULL;
|
|
+ refcount_set(&pi_state->refcount, 1);
|
|
+ current->pi_state_cache = pi_state;
|
|
+ }
|
|
+}
|
|
+
|
|
+/*
|
|
+ * We need to check the following states:
|
|
+ *
|
|
+ * Waiter | pi_state | pi->owner | uTID | uODIED | ?
|
|
+ *
|
|
+ * [1] NULL | --- | --- | 0 | 0/1 | Valid
|
|
+ * [2] NULL | --- | --- | >0 | 0/1 | Valid
|
|
+ *
|
|
+ * [3] Found | NULL | -- | Any | 0/1 | Invalid
|
|
+ *
|
|
+ * [4] Found | Found | NULL | 0 | 1 | Valid
|
|
+ * [5] Found | Found | NULL | >0 | 1 | Invalid
|
|
+ *
|
|
+ * [6] Found | Found | task | 0 | 1 | Valid
|
|
+ *
|
|
+ * [7] Found | Found | NULL | Any | 0 | Invalid
|
|
+ *
|
|
+ * [8] Found | Found | task | ==taskTID | 0/1 | Valid
|
|
+ * [9] Found | Found | task | 0 | 0 | Invalid
|
|
+ * [10] Found | Found | task | !=taskTID | 0/1 | Invalid
|
|
+ *
|
|
+ * [1] Indicates that the kernel can acquire the futex atomically. We
|
|
+ * came here due to a stale FUTEX_WAITERS/FUTEX_OWNER_DIED bit.
|
|
+ *
|
|
+ * [2] Valid, if TID does not belong to a kernel thread. If no matching
|
|
+ * thread is found then it indicates that the owner TID has died.
|
|
+ *
|
|
+ * [3] Invalid. The waiter is queued on a non PI futex
|
|
+ *
|
|
+ * [4] Valid state after exit_robust_list(), which sets the user space
|
|
+ * value to FUTEX_WAITERS | FUTEX_OWNER_DIED.
|
|
+ *
|
|
+ * [5] The user space value got manipulated between exit_robust_list()
|
|
+ * and exit_pi_state_list()
|
|
+ *
|
|
+ * [6] Valid state after exit_pi_state_list() which sets the new owner in
|
|
+ * the pi_state but cannot access the user space value.
|
|
+ *
|
|
+ * [7] pi_state->owner can only be NULL when the OWNER_DIED bit is set.
|
|
+ *
|
|
+ * [8] Owner and user space value match
|
|
+ *
|
|
+ * [9] There is no transient state which sets the user space TID to 0
|
|
+ * except exit_robust_list(), but this is indicated by the
|
|
+ * FUTEX_OWNER_DIED bit. See [4]
|
|
+ *
|
|
+ * [10] There is no transient state which leaves owner and user space
|
|
+ * TID out of sync. Except one error case where the kernel is denied
|
|
+ * write access to the user address, see fixup_pi_state_owner().
|
|
+ *
|
|
+ *
|
|
+ * Serialization and lifetime rules:
|
|
+ *
|
|
+ * hb->lock:
|
|
+ *
|
|
+ * hb -> futex_q, relation
|
|
+ * futex_q -> pi_state, relation
|
|
+ *
|
|
+ * (cannot be raw because hb can contain arbitrary amount
|
|
+ * of futex_q's)
|
|
+ *
|
|
+ * pi_mutex->wait_lock:
|
|
+ *
|
|
+ * {uval, pi_state}
|
|
+ *
|
|
+ * (and pi_mutex 'obviously')
|
|
+ *
|
|
+ * p->pi_lock:
|
|
+ *
|
|
+ * p->pi_state_list -> pi_state->list, relation
|
|
+ * pi_mutex->owner -> pi_state->owner, relation
|
|
+ *
|
|
+ * pi_state->refcount:
|
|
+ *
|
|
+ * pi_state lifetime
|
|
+ *
|
|
+ *
|
|
+ * Lock order:
|
|
+ *
|
|
+ * hb->lock
|
|
+ * pi_mutex->wait_lock
|
|
+ * p->pi_lock
|
|
+ *
|
|
+ */
|
|
+
|
|
+/*
|
|
+ * Validate that the existing waiter has a pi_state and sanity check
|
|
+ * the pi_state against the user space value. If correct, attach to
|
|
+ * it.
|
|
+ */
|
|
+static int attach_to_pi_state(u32 __user *uaddr, u32 uval,
|
|
+ struct futex_pi_state *pi_state,
|
|
+ struct futex_pi_state **ps)
|
|
+{
|
|
+ pid_t pid = uval & FUTEX_TID_MASK;
|
|
+ u32 uval2;
|
|
+ int ret;
|
|
+
|
|
+ /*
|
|
+ * Userspace might have messed up non-PI and PI futexes [3]
|
|
+ */
|
|
+ if (unlikely(!pi_state))
|
|
+ return -EINVAL;
|
|
+
|
|
+ /*
|
|
+ * We get here with hb->lock held, and having found a
|
|
+ * futex_top_waiter(). This means that futex_lock_pi() of said futex_q
|
|
+ * has dropped the hb->lock in between futex_queue() and futex_unqueue_pi(),
|
|
+ * which in turn means that futex_lock_pi() still has a reference on
|
|
+ * our pi_state.
|
|
+ *
|
|
+ * The waiter holding a reference on @pi_state also protects against
|
|
+ * the unlocked put_pi_state() in futex_unlock_pi(), futex_lock_pi()
|
|
+ * and futex_wait_requeue_pi() as it cannot go to 0 and consequently
|
|
+ * free pi_state before we can take a reference ourselves.
|
|
+ */
|
|
+ WARN_ON(!refcount_read(&pi_state->refcount));
|
|
+
|
|
+ /*
|
|
+ * Now that we have a pi_state, we can acquire wait_lock
|
|
+ * and do the state validation.
|
|
+ */
|
|
+ raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+
|
|
+ /*
|
|
+ * Since {uval, pi_state} is serialized by wait_lock, and our current
|
|
+ * uval was read without holding it, it can have changed. Verify it
|
|
+ * still is what we expect it to be, otherwise retry the entire
|
|
+ * operation.
|
|
+ */
|
|
+ if (futex_get_value_locked(&uval2, uaddr))
|
|
+ goto out_efault;
|
|
+
|
|
+ if (uval != uval2)
|
|
+ goto out_eagain;
|
|
+
|
|
+ /*
|
|
+ * Handle the owner died case:
|
|
+ */
|
|
+ if (uval & FUTEX_OWNER_DIED) {
|
|
+ /*
|
|
+ * exit_pi_state_list sets owner to NULL and wakes the
|
|
+ * topmost waiter. The task which acquires the
|
|
+ * pi_state->rt_mutex will fixup owner.
|
|
+ */
|
|
+ if (!pi_state->owner) {
|
|
+ /*
|
|
+ * No pi state owner, but the user space TID
|
|
+ * is not 0. Inconsistent state. [5]
|
|
+ */
|
|
+ if (pid)
|
|
+ goto out_einval;
|
|
+ /*
|
|
+ * Take a ref on the state and return success. [4]
|
|
+ */
|
|
+ goto out_attach;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * If TID is 0, then either the dying owner has not
|
|
+ * yet executed exit_pi_state_list() or some waiter
|
|
+ * acquired the rtmutex in the pi state, but did not
|
|
+ * yet fixup the TID in user space.
|
|
+ *
|
|
+ * Take a ref on the state and return success. [6]
|
|
+ */
|
|
+ if (!pid)
|
|
+ goto out_attach;
|
|
+ } else {
|
|
+ /*
|
|
+ * If the owner died bit is not set, then the pi_state
|
|
+ * must have an owner. [7]
|
|
+ */
|
|
+ if (!pi_state->owner)
|
|
+ goto out_einval;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * Bail out if user space manipulated the futex value. If pi
|
|
+ * state exists then the owner TID must be the same as the
|
|
+ * user space TID. [9/10]
|
|
+ */
|
|
+ if (pid != task_pid_vnr(pi_state->owner))
|
|
+ goto out_einval;
|
|
+
|
|
+out_attach:
|
|
+ get_pi_state(pi_state);
|
|
+ raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+ *ps = pi_state;
|
|
+ return 0;
|
|
+
|
|
+out_einval:
|
|
+ ret = -EINVAL;
|
|
+ goto out_error;
|
|
+
|
|
+out_eagain:
|
|
+ ret = -EAGAIN;
|
|
+ goto out_error;
|
|
+
|
|
+out_efault:
|
|
+ ret = -EFAULT;
|
|
+ goto out_error;
|
|
+
|
|
+out_error:
|
|
+ raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+static int handle_exit_race(u32 __user *uaddr, u32 uval,
|
|
+ struct task_struct *tsk)
|
|
+{
|
|
+ u32 uval2;
|
|
+
|
|
+ /*
|
|
+ * If the futex exit state is not yet FUTEX_STATE_DEAD, tell the
|
|
+ * caller that the alleged owner is busy.
|
|
+ */
|
|
+ if (tsk && tsk->futex_state != FUTEX_STATE_DEAD)
|
|
+ return -EBUSY;
|
|
+
|
|
+ /*
|
|
+ * Reread the user space value to handle the following situation:
|
|
+ *
|
|
+ * CPU0 CPU1
|
|
+ *
|
|
+ * sys_exit() sys_futex()
|
|
+ * do_exit() futex_lock_pi()
|
|
+ * futex_lock_pi_atomic()
|
|
+ * exit_signals(tsk) No waiters:
|
|
+ * tsk->flags |= PF_EXITING; *uaddr == 0x00000PID
|
|
+ * mm_release(tsk) Set waiter bit
|
|
+ * exit_robust_list(tsk) { *uaddr = 0x80000PID;
|
|
+ * Set owner died attach_to_pi_owner() {
|
|
+ * *uaddr = 0xC0000000; tsk = get_task(PID);
|
|
+ * } if (!tsk->flags & PF_EXITING) {
|
|
+ * ... attach();
|
|
+ * tsk->futex_state = } else {
|
|
+ * FUTEX_STATE_DEAD; if (tsk->futex_state !=
|
|
+ * FUTEX_STATE_DEAD)
|
|
+ * return -EAGAIN;
|
|
+ * return -ESRCH; <--- FAIL
|
|
+ * }
|
|
+ *
|
|
+ * Returning ESRCH unconditionally is wrong here because the
|
|
+ * user space value has been changed by the exiting task.
|
|
+ *
|
|
+ * The same logic applies to the case where the exiting task is
|
|
+ * already gone.
|
|
+ */
|
|
+ if (futex_get_value_locked(&uval2, uaddr))
|
|
+ return -EFAULT;
|
|
+
|
|
+ /* If the user space value has changed, try again. */
|
|
+ if (uval2 != uval)
|
|
+ return -EAGAIN;
|
|
+
|
|
+ /*
|
|
+ * The exiting task did not have a robust list, the robust list was
|
|
+ * corrupted or the user space value in *uaddr is simply bogus.
|
|
+ * Give up and tell user space.
|
|
+ */
|
|
+ return -ESRCH;
|
|
+}
|
|
+
|
|
+static void __attach_to_pi_owner(struct task_struct *p, union futex_key *key,
|
|
+ struct futex_pi_state **ps)
|
|
+{
|
|
+ /*
|
|
+ * No existing pi state. First waiter. [2]
|
|
+ *
|
|
+ * This creates pi_state, we have hb->lock held, this means nothing can
|
|
+ * observe this state, wait_lock is irrelevant.
|
|
+ */
|
|
+ struct futex_pi_state *pi_state = alloc_pi_state();
|
|
+
|
|
+ /*
|
|
+ * Initialize the pi_mutex in locked state and make @p
|
|
+ * the owner of it:
|
|
+ */
|
|
+ rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
|
|
+
|
|
+ /* Store the key for possible exit cleanups: */
|
|
+ pi_state->key = *key;
|
|
+
|
|
+ WARN_ON(!list_empty(&pi_state->list));
|
|
+ list_add(&pi_state->list, &p->pi_state_list);
|
|
+ /*
|
|
+ * Assignment without holding pi_state->pi_mutex.wait_lock is safe
|
|
+ * because there is no concurrency as the object is not published yet.
|
|
+ */
|
|
+ pi_state->owner = p;
|
|
+
|
|
+ *ps = pi_state;
|
|
+}
|
|
+/*
|
|
+ * Lookup the task for the TID provided from user space and attach to
|
|
+ * it after doing proper sanity checks.
|
|
+ */
|
|
+static int attach_to_pi_owner(u32 __user *uaddr, u32 uval, union futex_key *key,
|
|
+ struct futex_pi_state **ps,
|
|
+ struct task_struct **exiting)
|
|
+{
|
|
+ pid_t pid = uval & FUTEX_TID_MASK;
|
|
+ struct task_struct *p;
|
|
+
|
|
+ /*
|
|
+ * We are the first waiter - try to look up the real owner and attach
|
|
+ * the new pi_state to it, but bail out when TID = 0 [1]
|
|
+ *
|
|
+ * The !pid check is paranoid. None of the call sites should end up
|
|
+ * with pid == 0, but better safe than sorry. Let the caller retry
|
|
+ */
|
|
+ if (!pid)
|
|
+ return -EAGAIN;
|
|
+ p = find_get_task_by_vpid(pid);
|
|
+ if (!p)
|
|
+ return handle_exit_race(uaddr, uval, NULL);
|
|
+
|
|
+ if (unlikely(p->flags & PF_KTHREAD)) {
|
|
+ put_task_struct(p);
|
|
+ return -EPERM;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * We need to look at the task state to figure out, whether the
|
|
+ * task is exiting. To protect against the change of the task state
|
|
+ * in futex_exit_release(), we do this protected by p->pi_lock:
|
|
+ */
|
|
+ raw_spin_lock_irq(&p->pi_lock);
|
|
+ if (unlikely(p->futex_state != FUTEX_STATE_OK)) {
|
|
+ /*
|
|
+ * The task is on the way out. When the futex state is
|
|
+ * FUTEX_STATE_DEAD, we know that the task has finished
|
|
+ * the cleanup:
|
|
+ */
|
|
+ int ret = handle_exit_race(uaddr, uval, p);
|
|
+
|
|
+ raw_spin_unlock_irq(&p->pi_lock);
|
|
+ /*
|
|
+ * If the owner task is between FUTEX_STATE_EXITING and
|
|
+ * FUTEX_STATE_DEAD then store the task pointer and keep
|
|
+ * the reference on the task struct. The calling code will
|
|
+ * drop all locks, wait for the task to reach
|
|
+ * FUTEX_STATE_DEAD and then drop the refcount. This is
|
|
+ * required to prevent a live lock when the current task
|
|
+ * preempted the exiting task between the two states.
|
|
+ */
|
|
+ if (ret == -EBUSY)
|
|
+ *exiting = p;
|
|
+ else
|
|
+ put_task_struct(p);
|
|
+ return ret;
|
|
+ }
|
|
+
|
|
+ __attach_to_pi_owner(p, key, ps);
|
|
+ raw_spin_unlock_irq(&p->pi_lock);
|
|
+
|
|
+ put_task_struct(p);
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval)
|
|
+{
|
|
+ int err;
|
|
+ u32 curval;
|
|
+
|
|
+ if (unlikely(should_fail_futex(true)))
|
|
+ return -EFAULT;
|
|
+
|
|
+ err = futex_cmpxchg_value_locked(&curval, uaddr, uval, newval);
|
|
+ if (unlikely(err))
|
|
+ return err;
|
|
+
|
|
+ /* If user space value changed, let the caller retry */
|
|
+ return curval != uval ? -EAGAIN : 0;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex
|
|
+ * @uaddr: the pi futex user address
|
|
+ * @hb: the pi futex hash bucket
|
|
+ * @key: the futex key associated with uaddr and hb
|
|
+ * @ps: the pi_state pointer where we store the result of the
|
|
+ * lookup
|
|
+ * @task: the task to perform the atomic lock work for. This will
|
|
+ * be "current" except in the case of requeue pi.
|
|
+ * @exiting: Pointer to store the task pointer of the owner task
|
|
+ * which is in the middle of exiting
|
|
+ * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
|
|
+ *
|
|
+ * Return:
|
|
+ * - 0 - ready to wait;
|
|
+ * - 1 - acquired the lock;
|
|
+ * - <0 - error
|
|
+ *
|
|
+ * The hb->lock must be held by the caller.
|
|
+ *
|
|
+ * @exiting is only set when the return value is -EBUSY. If so, this holds
|
|
+ * a refcount on the exiting task on return and the caller needs to drop it
|
|
+ * after waiting for the exit to complete.
|
|
+ */
|
|
+int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
|
|
+ union futex_key *key,
|
|
+ struct futex_pi_state **ps,
|
|
+ struct task_struct *task,
|
|
+ struct task_struct **exiting,
|
|
+ int set_waiters)
|
|
+{
|
|
+ u32 uval, newval, vpid = task_pid_vnr(task);
|
|
+ struct futex_q *top_waiter;
|
|
+ int ret;
|
|
+
|
|
+ /*
|
|
+ * Read the user space value first so we can validate a few
|
|
+ * things before proceeding further.
|
|
+ */
|
|
+ if (futex_get_value_locked(&uval, uaddr))
|
|
+ return -EFAULT;
|
|
+
|
|
+ if (unlikely(should_fail_futex(true)))
|
|
+ return -EFAULT;
|
|
+
|
|
+ /*
|
|
+ * Detect deadlocks.
|
|
+ */
|
|
+ if ((unlikely((uval & FUTEX_TID_MASK) == vpid)))
|
|
+ return -EDEADLK;
|
|
+
|
|
+ if ((unlikely(should_fail_futex(true))))
|
|
+ return -EDEADLK;
|
|
+
|
|
+ /*
|
|
+ * Lookup existing state first. If it exists, try to attach to
|
|
+ * its pi_state.
|
|
+ */
|
|
+ top_waiter = futex_top_waiter(hb, key);
|
|
+ if (top_waiter)
|
|
+ return attach_to_pi_state(uaddr, uval, top_waiter->pi_state, ps);
|
|
+
|
|
+ /*
|
|
+ * No waiter and user TID is 0. We are here because the
|
|
+ * waiters or the owner died bit is set or called from
|
|
+ * requeue_cmp_pi or for whatever reason something took the
|
|
+ * syscall.
|
|
+ */
|
|
+ if (!(uval & FUTEX_TID_MASK)) {
|
|
+ /*
|
|
+ * We take over the futex. No other waiters and the user space
|
|
+ * TID is 0. We preserve the owner died bit.
|
|
+ */
|
|
+ newval = uval & FUTEX_OWNER_DIED;
|
|
+ newval |= vpid;
|
|
+
|
|
+ /* The futex requeue_pi code can enforce the waiters bit */
|
|
+ if (set_waiters)
|
|
+ newval |= FUTEX_WAITERS;
|
|
+
|
|
+ ret = lock_pi_update_atomic(uaddr, uval, newval);
|
|
+ if (ret)
|
|
+ return ret;
|
|
+
|
|
+ /*
|
|
+ * If the waiter bit was requested the caller also needs PI
|
|
+ * state attached to the new owner of the user space futex.
|
|
+ *
|
|
+ * @task is guaranteed to be alive and it cannot be exiting
|
|
+ * because it is either sleeping or waiting in
|
|
+ * futex_requeue_pi_wakeup_sync().
|
|
+ *
|
|
+ * No need to do the full attach_to_pi_owner() exercise
|
|
+ * because @task is known and valid.
|
|
+ */
|
|
+ if (set_waiters) {
|
|
+ raw_spin_lock_irq(&task->pi_lock);
|
|
+ __attach_to_pi_owner(task, key, ps);
|
|
+ raw_spin_unlock_irq(&task->pi_lock);
|
|
+ }
|
|
+ return 1;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * First waiter. Set the waiters bit before attaching ourself to
|
|
+ * the owner. If owner tries to unlock, it will be forced into
|
|
+ * the kernel and blocked on hb->lock.
|
|
+ */
|
|
+ newval = uval | FUTEX_WAITERS;
|
|
+ ret = lock_pi_update_atomic(uaddr, uval, newval);
|
|
+ if (ret)
|
|
+ return ret;
|
|
+ /*
|
|
+ * If the update of the user space value succeeded, we try to
|
|
+ * attach to the owner. If that fails, no harm done, we only
|
|
+ * set the FUTEX_WAITERS bit in the user space variable.
|
|
+ */
|
|
+ return attach_to_pi_owner(uaddr, newval, key, ps, exiting);
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Caller must hold a reference on @pi_state.
|
|
+ */
|
|
+static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_state)
|
|
+{
|
|
+ struct rt_mutex_waiter *top_waiter;
|
|
+ struct task_struct *new_owner;
|
|
+ bool postunlock = false;
|
|
+ DEFINE_RT_WAKE_Q(wqh);
|
|
+ u32 curval, newval;
|
|
+ int ret = 0;
|
|
+
|
|
+ top_waiter = rt_mutex_top_waiter(&pi_state->pi_mutex);
|
|
+ if (WARN_ON_ONCE(!top_waiter)) {
|
|
+ /*
|
|
+ * As per the comment in futex_unlock_pi() this should not happen.
|
|
+ *
|
|
+ * When this happens, give up our locks and try again, giving
|
|
+ * the futex_lock_pi() instance time to complete, either by
|
|
+ * waiting on the rtmutex or removing itself from the futex
|
|
+ * queue.
|
|
+ */
|
|
+ ret = -EAGAIN;
|
|
+ goto out_unlock;
|
|
+ }
|
|
+
|
|
+ new_owner = top_waiter->task;
|
|
+
|
|
+ /*
|
|
+ * We pass it to the next owner. The WAITERS bit is always kept
|
|
+ * enabled while there is PI state around. We cleanup the owner
|
|
+ * died bit, because we are the owner.
|
|
+ */
|
|
+ newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
|
|
+
|
|
+ if (unlikely(should_fail_futex(true))) {
|
|
+ ret = -EFAULT;
|
|
+ goto out_unlock;
|
|
+ }
|
|
+
|
|
+ ret = futex_cmpxchg_value_locked(&curval, uaddr, uval, newval);
|
|
+ if (!ret && (curval != uval)) {
|
|
+ /*
|
|
+ * If a unconditional UNLOCK_PI operation (user space did not
|
|
+ * try the TID->0 transition) raced with a waiter setting the
|
|
+ * FUTEX_WAITERS flag between get_user() and locking the hash
|
|
+ * bucket lock, retry the operation.
|
|
+ */
|
|
+ if ((FUTEX_TID_MASK & curval) == uval)
|
|
+ ret = -EAGAIN;
|
|
+ else
|
|
+ ret = -EINVAL;
|
|
+ }
|
|
+
|
|
+ if (!ret) {
|
|
+ /*
|
|
+ * This is a point of no return; once we modified the uval
|
|
+ * there is no going back and subsequent operations must
|
|
+ * not fail.
|
|
+ */
|
|
+ pi_state_update_owner(pi_state, new_owner);
|
|
+ postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wqh);
|
|
+ }
|
|
+
|
|
+out_unlock:
|
|
+ raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+
|
|
+ if (postunlock)
|
|
+ rt_mutex_postunlock(&wqh);
|
|
+
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
|
|
+ struct task_struct *argowner)
|
|
+{
|
|
+ struct futex_pi_state *pi_state = q->pi_state;
|
|
+ struct task_struct *oldowner, *newowner;
|
|
+ u32 uval, curval, newval, newtid;
|
|
+ int err = 0;
|
|
+
|
|
+ oldowner = pi_state->owner;
|
|
+
|
|
+ /*
|
|
+ * We are here because either:
|
|
+ *
|
|
+ * - we stole the lock and pi_state->owner needs updating to reflect
|
|
+ * that (@argowner == current),
|
|
+ *
|
|
+ * or:
|
|
+ *
|
|
+ * - someone stole our lock and we need to fix things to point to the
|
|
+ * new owner (@argowner == NULL).
|
|
+ *
|
|
+ * Either way, we have to replace the TID in the user space variable.
|
|
+ * This must be atomic as we have to preserve the owner died bit here.
|
|
+ *
|
|
+ * Note: We write the user space value _before_ changing the pi_state
|
|
+ * because we can fault here. Imagine swapped out pages or a fork
|
|
+ * that marked all the anonymous memory readonly for cow.
|
|
+ *
|
|
+ * Modifying pi_state _before_ the user space value would leave the
|
|
+ * pi_state in an inconsistent state when we fault here, because we
|
|
+ * need to drop the locks to handle the fault. This might be observed
|
|
+ * in the PID checks when attaching to PI state .
|
|
+ */
|
|
+retry:
|
|
+ if (!argowner) {
|
|
+ if (oldowner != current) {
|
|
+ /*
|
|
+ * We raced against a concurrent self; things are
|
|
+ * already fixed up. Nothing to do.
|
|
+ */
|
|
+ return 0;
|
|
+ }
|
|
+
|
|
+ if (__rt_mutex_futex_trylock(&pi_state->pi_mutex)) {
|
|
+ /* We got the lock. pi_state is correct. Tell caller. */
|
|
+ return 1;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * The trylock just failed, so either there is an owner or
|
|
+ * there is a higher priority waiter than this one.
|
|
+ */
|
|
+ newowner = rt_mutex_owner(&pi_state->pi_mutex);
|
|
+ /*
|
|
+ * If the higher priority waiter has not yet taken over the
|
|
+ * rtmutex then newowner is NULL. We can't return here with
|
|
+ * that state because it's inconsistent vs. the user space
|
|
+ * state. So drop the locks and try again. It's a valid
|
|
+ * situation and not any different from the other retry
|
|
+ * conditions.
|
|
+ */
|
|
+ if (unlikely(!newowner)) {
|
|
+ err = -EAGAIN;
|
|
+ goto handle_err;
|
|
+ }
|
|
+ } else {
|
|
+ WARN_ON_ONCE(argowner != current);
|
|
+ if (oldowner == current) {
|
|
+ /*
|
|
+ * We raced against a concurrent self; things are
|
|
+ * already fixed up. Nothing to do.
|
|
+ */
|
|
+ return 1;
|
|
+ }
|
|
+ newowner = argowner;
|
|
+ }
|
|
+
|
|
+ newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
|
|
+ /* Owner died? */
|
|
+ if (!pi_state->owner)
|
|
+ newtid |= FUTEX_OWNER_DIED;
|
|
+
|
|
+ err = futex_get_value_locked(&uval, uaddr);
|
|
+ if (err)
|
|
+ goto handle_err;
|
|
+
|
|
+ for (;;) {
|
|
+ newval = (uval & FUTEX_OWNER_DIED) | newtid;
|
|
+
|
|
+ err = futex_cmpxchg_value_locked(&curval, uaddr, uval, newval);
|
|
+ if (err)
|
|
+ goto handle_err;
|
|
+
|
|
+ if (curval == uval)
|
|
+ break;
|
|
+ uval = curval;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * We fixed up user space. Now we need to fix the pi_state
|
|
+ * itself.
|
|
+ */
|
|
+ pi_state_update_owner(pi_state, newowner);
|
|
+
|
|
+ return argowner == current;
|
|
+
|
|
+ /*
|
|
+ * In order to reschedule or handle a page fault, we need to drop the
|
|
+ * locks here. In the case of a fault, this gives the other task
|
|
+ * (either the highest priority waiter itself or the task which stole
|
|
+ * the rtmutex) the chance to try the fixup of the pi_state. So once we
|
|
+ * are back from handling the fault we need to check the pi_state after
|
|
+ * reacquiring the locks and before trying to do another fixup. When
|
|
+ * the fixup has been done already we simply return.
|
|
+ *
|
|
+ * Note: we hold both hb->lock and pi_mutex->wait_lock. We can safely
|
|
+ * drop hb->lock since the caller owns the hb -> futex_q relation.
|
|
+ * Dropping the pi_mutex->wait_lock requires the state revalidate.
|
|
+ */
|
|
+handle_err:
|
|
+ raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+ spin_unlock(q->lock_ptr);
|
|
+
|
|
+ switch (err) {
|
|
+ case -EFAULT:
|
|
+ err = fault_in_user_writeable(uaddr);
|
|
+ break;
|
|
+
|
|
+ case -EAGAIN:
|
|
+ cond_resched();
|
|
+ err = 0;
|
|
+ break;
|
|
+
|
|
+ default:
|
|
+ WARN_ON_ONCE(1);
|
|
+ break;
|
|
+ }
|
|
+
|
|
+ spin_lock(q->lock_ptr);
|
|
+ raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+
|
|
+ /*
|
|
+ * Check if someone else fixed it for us:
|
|
+ */
|
|
+ if (pi_state->owner != oldowner)
|
|
+ return argowner == current;
|
|
+
|
|
+ /* Retry if err was -EAGAIN or the fault in succeeded */
|
|
+ if (!err)
|
|
+ goto retry;
|
|
+
|
|
+ /*
|
|
+ * fault_in_user_writeable() failed so user state is immutable. At
|
|
+ * best we can make the kernel state consistent but user state will
|
|
+ * be most likely hosed and any subsequent unlock operation will be
|
|
+ * rejected due to PI futex rule [10].
|
|
+ *
|
|
+ * Ensure that the rtmutex owner is also the pi_state owner despite
|
|
+ * the user space value claiming something different. There is no
|
|
+ * point in unlocking the rtmutex if current is the owner as it
|
|
+ * would need to wait until the next waiter has taken the rtmutex
|
|
+ * to guarantee consistent state. Keep it simple. Userspace asked
|
|
+ * for this wreckaged state.
|
|
+ *
|
|
+ * The rtmutex has an owner - either current or some other
|
|
+ * task. See the EAGAIN loop above.
|
|
+ */
|
|
+ pi_state_update_owner(pi_state, rt_mutex_owner(&pi_state->pi_mutex));
|
|
+
|
|
+ return err;
|
|
+}
|
|
+
|
|
+static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
|
|
+ struct task_struct *argowner)
|
|
+{
|
|
+ struct futex_pi_state *pi_state = q->pi_state;
|
|
+ int ret;
|
|
+
|
|
+ lockdep_assert_held(q->lock_ptr);
|
|
+
|
|
+ raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+ ret = __fixup_pi_state_owner(uaddr, q, argowner);
|
|
+ raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * fixup_pi_owner() - Post lock pi_state and corner case management
|
|
+ * @uaddr: user address of the futex
|
|
+ * @q: futex_q (contains pi_state and access to the rt_mutex)
|
|
+ * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0)
|
|
+ *
|
|
+ * After attempting to lock an rt_mutex, this function is called to cleanup
|
|
+ * the pi_state owner as well as handle race conditions that may allow us to
|
|
+ * acquire the lock. Must be called with the hb lock held.
|
|
+ *
|
|
+ * Return:
|
|
+ * - 1 - success, lock taken;
|
|
+ * - 0 - success, lock not taken;
|
|
+ * - <0 - on error (-EFAULT)
|
|
+ */
|
|
+int fixup_pi_owner(u32 __user *uaddr, struct futex_q *q, int locked)
|
|
+{
|
|
+ if (locked) {
|
|
+ /*
|
|
+ * Got the lock. We might not be the anticipated owner if we
|
|
+ * did a lock-steal - fix up the PI-state in that case:
|
|
+ *
|
|
+ * Speculative pi_state->owner read (we don't hold wait_lock);
|
|
+ * since we own the lock pi_state->owner == current is the
|
|
+ * stable state, anything else needs more attention.
|
|
+ */
|
|
+ if (q->pi_state->owner != current)
|
|
+ return fixup_pi_state_owner(uaddr, q, current);
|
|
+ return 1;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * If we didn't get the lock; check if anybody stole it from us. In
|
|
+ * that case, we need to fix up the uval to point to them instead of
|
|
+ * us, otherwise bad things happen. [10]
|
|
+ *
|
|
+ * Another speculative read; pi_state->owner == current is unstable
|
|
+ * but needs our attention.
|
|
+ */
|
|
+ if (q->pi_state->owner == current)
|
|
+ return fixup_pi_state_owner(uaddr, q, NULL);
|
|
+
|
|
+ /*
|
|
+ * Paranoia check. If we did not take the lock, then we should not be
|
|
+ * the owner of the rt_mutex. Warn and establish consistent state.
|
|
+ */
|
|
+ if (WARN_ON_ONCE(rt_mutex_owner(&q->pi_state->pi_mutex) == current))
|
|
+ return fixup_pi_state_owner(uaddr, q, current);
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Userspace tried a 0 -> TID atomic transition of the futex value
|
|
+ * and failed. The kernel side here does the whole locking operation:
|
|
+ * if there are waiters then it will block as a consequence of relying
|
|
+ * on rt-mutexes, it does PI, etc. (Due to races the kernel might see
|
|
+ * a 0 value of the futex too.).
|
|
+ *
|
|
+ * Also serves as futex trylock_pi()'ing, and due semantics.
|
|
+ */
|
|
+int futex_lock_pi(u32 __user *uaddr, unsigned int flags, ktime_t *time, int trylock)
|
|
+{
|
|
+ struct hrtimer_sleeper timeout, *to;
|
|
+ struct task_struct *exiting = NULL;
|
|
+ struct rt_mutex_waiter rt_waiter;
|
|
+ struct futex_hash_bucket *hb;
|
|
+ struct futex_q q = futex_q_init;
|
|
+ int res, ret;
|
|
+
|
|
+ if (!IS_ENABLED(CONFIG_FUTEX_PI))
|
|
+ return -ENOSYS;
|
|
+
|
|
+ if (refill_pi_state_cache())
|
|
+ return -ENOMEM;
|
|
+
|
|
+ to = futex_setup_timer(time, &timeout, flags, 0);
|
|
+
|
|
+retry:
|
|
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key, FUTEX_WRITE);
|
|
+ if (unlikely(ret != 0))
|
|
+ goto out;
|
|
+
|
|
+retry_private:
|
|
+ hb = futex_q_lock(&q);
|
|
+
|
|
+ ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current,
|
|
+ &exiting, 0);
|
|
+ if (unlikely(ret)) {
|
|
+ /*
|
|
+ * Atomic work succeeded and we got the lock,
|
|
+ * or failed. Either way, we do _not_ block.
|
|
+ */
|
|
+ switch (ret) {
|
|
+ case 1:
|
|
+ /* We got the lock. */
|
|
+ ret = 0;
|
|
+ goto out_unlock_put_key;
|
|
+ case -EFAULT:
|
|
+ goto uaddr_faulted;
|
|
+ case -EBUSY:
|
|
+ case -EAGAIN:
|
|
+ /*
|
|
+ * Two reasons for this:
|
|
+ * - EBUSY: Task is exiting and we just wait for the
|
|
+ * exit to complete.
|
|
+ * - EAGAIN: The user space value changed.
|
|
+ */
|
|
+ futex_q_unlock(hb);
|
|
+ /*
|
|
+ * Handle the case where the owner is in the middle of
|
|
+ * exiting. Wait for the exit to complete otherwise
|
|
+ * this task might loop forever, aka. live lock.
|
|
+ */
|
|
+ wait_for_owner_exiting(ret, exiting);
|
|
+ cond_resched();
|
|
+ goto retry;
|
|
+ default:
|
|
+ goto out_unlock_put_key;
|
|
+ }
|
|
+ }
|
|
+
|
|
+ WARN_ON(!q.pi_state);
|
|
+
|
|
+ /*
|
|
+ * Only actually queue now that the atomic ops are done:
|
|
+ */
|
|
+ __futex_queue(&q, hb);
|
|
+
|
|
+ if (trylock) {
|
|
+ ret = rt_mutex_futex_trylock(&q.pi_state->pi_mutex);
|
|
+ /* Fixup the trylock return value: */
|
|
+ ret = ret ? 0 : -EWOULDBLOCK;
|
|
+ goto no_block;
|
|
+ }
|
|
+
|
|
+ rt_mutex_init_waiter(&rt_waiter);
|
|
+
|
|
+ /*
|
|
+ * On PREEMPT_RT_FULL, when hb->lock becomes an rt_mutex, we must not
|
|
+ * hold it while doing rt_mutex_start_proxy(), because then it will
|
|
+ * include hb->lock in the blocking chain, even through we'll not in
|
|
+ * fact hold it while blocking. This will lead it to report -EDEADLK
|
|
+ * and BUG when futex_unlock_pi() interleaves with this.
|
|
+ *
|
|
+ * Therefore acquire wait_lock while holding hb->lock, but drop the
|
|
+ * latter before calling __rt_mutex_start_proxy_lock(). This
|
|
+ * interleaves with futex_unlock_pi() -- which does a similar lock
|
|
+ * handoff -- such that the latter can observe the futex_q::pi_state
|
|
+ * before __rt_mutex_start_proxy_lock() is done.
|
|
+ */
|
|
+ raw_spin_lock_irq(&q.pi_state->pi_mutex.wait_lock);
|
|
+ spin_unlock(q.lock_ptr);
|
|
+ /*
|
|
+ * __rt_mutex_start_proxy_lock() unconditionally enqueues the @rt_waiter
|
|
+ * such that futex_unlock_pi() is guaranteed to observe the waiter when
|
|
+ * it sees the futex_q::pi_state.
|
|
+ */
|
|
+ ret = __rt_mutex_start_proxy_lock(&q.pi_state->pi_mutex, &rt_waiter, current);
|
|
+ raw_spin_unlock_irq(&q.pi_state->pi_mutex.wait_lock);
|
|
+
|
|
+ if (ret) {
|
|
+ if (ret == 1)
|
|
+ ret = 0;
|
|
+ goto cleanup;
|
|
+ }
|
|
+
|
|
+ if (unlikely(to))
|
|
+ hrtimer_sleeper_start_expires(to, HRTIMER_MODE_ABS);
|
|
+
|
|
+ ret = rt_mutex_wait_proxy_lock(&q.pi_state->pi_mutex, to, &rt_waiter);
|
|
+
|
|
+cleanup:
|
|
+ spin_lock(q.lock_ptr);
|
|
+ /*
|
|
+ * If we failed to acquire the lock (deadlock/signal/timeout), we must
|
|
+ * first acquire the hb->lock before removing the lock from the
|
|
+ * rt_mutex waitqueue, such that we can keep the hb and rt_mutex wait
|
|
+ * lists consistent.
|
|
+ *
|
|
+ * In particular; it is important that futex_unlock_pi() can not
|
|
+ * observe this inconsistency.
|
|
+ */
|
|
+ if (ret && !rt_mutex_cleanup_proxy_lock(&q.pi_state->pi_mutex, &rt_waiter))
|
|
+ ret = 0;
|
|
+
|
|
+no_block:
|
|
+ /*
|
|
+ * Fixup the pi_state owner and possibly acquire the lock if we
|
|
+ * haven't already.
|
|
+ */
|
|
+ res = fixup_pi_owner(uaddr, &q, !ret);
|
|
+ /*
|
|
+ * If fixup_pi_owner() returned an error, propagate that. If it acquired
|
|
+ * the lock, clear our -ETIMEDOUT or -EINTR.
|
|
+ */
|
|
+ if (res)
|
|
+ ret = (res < 0) ? res : 0;
|
|
+
|
|
+ futex_unqueue_pi(&q);
|
|
+ spin_unlock(q.lock_ptr);
|
|
+ goto out;
|
|
+
|
|
+out_unlock_put_key:
|
|
+ futex_q_unlock(hb);
|
|
+
|
|
+out:
|
|
+ if (to) {
|
|
+ hrtimer_cancel(&to->timer);
|
|
+ destroy_hrtimer_on_stack(&to->timer);
|
|
+ }
|
|
+ return ret != -EINTR ? ret : -ERESTARTNOINTR;
|
|
+
|
|
+uaddr_faulted:
|
|
+ futex_q_unlock(hb);
|
|
+
|
|
+ ret = fault_in_user_writeable(uaddr);
|
|
+ if (ret)
|
|
+ goto out;
|
|
+
|
|
+ if (!(flags & FLAGS_SHARED))
|
|
+ goto retry_private;
|
|
+
|
|
+ goto retry;
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Userspace attempted a TID -> 0 atomic transition, and failed.
|
|
+ * This is the in-kernel slowpath: we look up the PI state (if any),
|
|
+ * and do the rt-mutex unlock.
|
|
+ */
|
|
+int futex_unlock_pi(u32 __user *uaddr, unsigned int flags)
|
|
+{
|
|
+ u32 curval, uval, vpid = task_pid_vnr(current);
|
|
+ union futex_key key = FUTEX_KEY_INIT;
|
|
+ struct futex_hash_bucket *hb;
|
|
+ struct futex_q *top_waiter;
|
|
+ int ret;
|
|
+
|
|
+ if (!IS_ENABLED(CONFIG_FUTEX_PI))
|
|
+ return -ENOSYS;
|
|
+
|
|
+retry:
|
|
+ if (get_user(uval, uaddr))
|
|
+ return -EFAULT;
|
|
+ /*
|
|
+ * We release only a lock we actually own:
|
|
+ */
|
|
+ if ((uval & FUTEX_TID_MASK) != vpid)
|
|
+ return -EPERM;
|
|
+
|
|
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, FUTEX_WRITE);
|
|
+ if (ret)
|
|
+ return ret;
|
|
+
|
|
+ hb = futex_hash(&key);
|
|
+ spin_lock(&hb->lock);
|
|
+
|
|
+ /*
|
|
+ * Check waiters first. We do not trust user space values at
|
|
+ * all and we at least want to know if user space fiddled
|
|
+ * with the futex value instead of blindly unlocking.
|
|
+ */
|
|
+ top_waiter = futex_top_waiter(hb, &key);
|
|
+ if (top_waiter) {
|
|
+ struct futex_pi_state *pi_state = top_waiter->pi_state;
|
|
+
|
|
+ ret = -EINVAL;
|
|
+ if (!pi_state)
|
|
+ goto out_unlock;
|
|
+
|
|
+ /*
|
|
+ * If current does not own the pi_state then the futex is
|
|
+ * inconsistent and user space fiddled with the futex value.
|
|
+ */
|
|
+ if (pi_state->owner != current)
|
|
+ goto out_unlock;
|
|
+
|
|
+ get_pi_state(pi_state);
|
|
+ /*
|
|
+ * By taking wait_lock while still holding hb->lock, we ensure
|
|
+ * there is no point where we hold neither; and therefore
|
|
+ * wake_futex_p() must observe a state consistent with what we
|
|
+ * observed.
|
|
+ *
|
|
+ * In particular; this forces __rt_mutex_start_proxy() to
|
|
+ * complete such that we're guaranteed to observe the
|
|
+ * rt_waiter. Also see the WARN in wake_futex_pi().
|
|
+ */
|
|
+ raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+ spin_unlock(&hb->lock);
|
|
+
|
|
+ /* drops pi_state->pi_mutex.wait_lock */
|
|
+ ret = wake_futex_pi(uaddr, uval, pi_state);
|
|
+
|
|
+ put_pi_state(pi_state);
|
|
+
|
|
+ /*
|
|
+ * Success, we're done! No tricky corner cases.
|
|
+ */
|
|
+ if (!ret)
|
|
+ return ret;
|
|
+ /*
|
|
+ * The atomic access to the futex value generated a
|
|
+ * pagefault, so retry the user-access and the wakeup:
|
|
+ */
|
|
+ if (ret == -EFAULT)
|
|
+ goto pi_faulted;
|
|
+ /*
|
|
+ * A unconditional UNLOCK_PI op raced against a waiter
|
|
+ * setting the FUTEX_WAITERS bit. Try again.
|
|
+ */
|
|
+ if (ret == -EAGAIN)
|
|
+ goto pi_retry;
|
|
+ /*
|
|
+ * wake_futex_pi has detected invalid state. Tell user
|
|
+ * space.
|
|
+ */
|
|
+ return ret;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * We have no kernel internal state, i.e. no waiters in the
|
|
+ * kernel. Waiters which are about to queue themselves are stuck
|
|
+ * on hb->lock. So we can safely ignore them. We do neither
|
|
+ * preserve the WAITERS bit not the OWNER_DIED one. We are the
|
|
+ * owner.
|
|
+ */
|
|
+ if ((ret = futex_cmpxchg_value_locked(&curval, uaddr, uval, 0))) {
|
|
+ spin_unlock(&hb->lock);
|
|
+ switch (ret) {
|
|
+ case -EFAULT:
|
|
+ goto pi_faulted;
|
|
+
|
|
+ case -EAGAIN:
|
|
+ goto pi_retry;
|
|
+
|
|
+ default:
|
|
+ WARN_ON_ONCE(1);
|
|
+ return ret;
|
|
+ }
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * If uval has changed, let user space handle it.
|
|
+ */
|
|
+ ret = (curval == uval) ? 0 : -EAGAIN;
|
|
+
|
|
+out_unlock:
|
|
+ spin_unlock(&hb->lock);
|
|
+ return ret;
|
|
+
|
|
+pi_retry:
|
|
+ cond_resched();
|
|
+ goto retry;
|
|
+
|
|
+pi_faulted:
|
|
+
|
|
+ ret = fault_in_user_writeable(uaddr);
|
|
+ if (!ret)
|
|
+ goto retry;
|
|
+
|
|
+ return ret;
|
|
+}
|
|
+
|
|
diff --git a/kernel/futex/requeue.c b/kernel/futex/requeue.c
|
|
new file mode 100644
|
|
index 000000000..cba8b1a6a
|
|
--- /dev/null
|
|
+++ b/kernel/futex/requeue.c
|
|
@@ -0,0 +1,897 @@
|
|
+// SPDX-License-Identifier: GPL-2.0-or-later
|
|
+
|
|
+#include <linux/sched/signal.h>
|
|
+
|
|
+#include "futex.h"
|
|
+#include "../locking/rtmutex_common.h"
|
|
+
|
|
+/*
|
|
+ * On PREEMPT_RT, the hash bucket lock is a 'sleeping' spinlock with an
|
|
+ * underlying rtmutex. The task which is about to be requeued could have
|
|
+ * just woken up (timeout, signal). After the wake up the task has to
|
|
+ * acquire hash bucket lock, which is held by the requeue code. As a task
|
|
+ * can only be blocked on _ONE_ rtmutex at a time, the proxy lock blocking
|
|
+ * and the hash bucket lock blocking would collide and corrupt state.
|
|
+ *
|
|
+ * On !PREEMPT_RT this is not a problem and everything could be serialized
|
|
+ * on hash bucket lock, but aside of having the benefit of common code,
|
|
+ * this allows to avoid doing the requeue when the task is already on the
|
|
+ * way out and taking the hash bucket lock of the original uaddr1 when the
|
|
+ * requeue has been completed.
|
|
+ *
|
|
+ * The following state transitions are valid:
|
|
+ *
|
|
+ * On the waiter side:
|
|
+ * Q_REQUEUE_PI_NONE -> Q_REQUEUE_PI_IGNORE
|
|
+ * Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_WAIT
|
|
+ *
|
|
+ * On the requeue side:
|
|
+ * Q_REQUEUE_PI_NONE -> Q_REQUEUE_PI_INPROGRESS
|
|
+ * Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_DONE/LOCKED
|
|
+ * Q_REQUEUE_PI_IN_PROGRESS -> Q_REQUEUE_PI_NONE (requeue failed)
|
|
+ * Q_REQUEUE_PI_WAIT -> Q_REQUEUE_PI_DONE/LOCKED
|
|
+ * Q_REQUEUE_PI_WAIT -> Q_REQUEUE_PI_IGNORE (requeue failed)
|
|
+ *
|
|
+ * The requeue side ignores a waiter with state Q_REQUEUE_PI_IGNORE as this
|
|
+ * signals that the waiter is already on the way out. It also means that
|
|
+ * the waiter is still on the 'wait' futex, i.e. uaddr1.
|
|
+ *
|
|
+ * The waiter side signals early wakeup to the requeue side either through
|
|
+ * setting state to Q_REQUEUE_PI_IGNORE or to Q_REQUEUE_PI_WAIT depending
|
|
+ * on the current state. In case of Q_REQUEUE_PI_IGNORE it can immediately
|
|
+ * proceed to take the hash bucket lock of uaddr1. If it set state to WAIT,
|
|
+ * which means the wakeup is interleaving with a requeue in progress it has
|
|
+ * to wait for the requeue side to change the state. Either to DONE/LOCKED
|
|
+ * or to IGNORE. DONE/LOCKED means the waiter q is now on the uaddr2 futex
|
|
+ * and either blocked (DONE) or has acquired it (LOCKED). IGNORE is set by
|
|
+ * the requeue side when the requeue attempt failed via deadlock detection
|
|
+ * and therefore the waiter q is still on the uaddr1 futex.
|
|
+ */
|
|
+enum {
|
|
+ Q_REQUEUE_PI_NONE = 0,
|
|
+ Q_REQUEUE_PI_IGNORE,
|
|
+ Q_REQUEUE_PI_IN_PROGRESS,
|
|
+ Q_REQUEUE_PI_WAIT,
|
|
+ Q_REQUEUE_PI_DONE,
|
|
+ Q_REQUEUE_PI_LOCKED,
|
|
+};
|
|
+
|
|
+const struct futex_q futex_q_init = {
|
|
+ /* list gets initialized in futex_queue()*/
|
|
+ .key = FUTEX_KEY_INIT,
|
|
+ .bitset = FUTEX_BITSET_MATCH_ANY,
|
|
+ .requeue_state = ATOMIC_INIT(Q_REQUEUE_PI_NONE),
|
|
+};
|
|
+
|
|
+/**
|
|
+ * requeue_futex() - Requeue a futex_q from one hb to another
|
|
+ * @q: the futex_q to requeue
|
|
+ * @hb1: the source hash_bucket
|
|
+ * @hb2: the target hash_bucket
|
|
+ * @key2: the new key for the requeued futex_q
|
|
+ */
|
|
+static inline
|
|
+void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1,
|
|
+ struct futex_hash_bucket *hb2, union futex_key *key2)
|
|
+{
|
|
+
|
|
+ /*
|
|
+ * If key1 and key2 hash to the same bucket, no need to
|
|
+ * requeue.
|
|
+ */
|
|
+ if (likely(&hb1->chain != &hb2->chain)) {
|
|
+ plist_del(&q->list, &hb1->chain);
|
|
+ futex_hb_waiters_dec(hb1);
|
|
+ futex_hb_waiters_inc(hb2);
|
|
+ plist_add(&q->list, &hb2->chain);
|
|
+ q->lock_ptr = &hb2->lock;
|
|
+ }
|
|
+ q->key = *key2;
|
|
+}
|
|
+
|
|
+static inline bool futex_requeue_pi_prepare(struct futex_q *q,
|
|
+ struct futex_pi_state *pi_state)
|
|
+{
|
|
+ int old, new;
|
|
+
|
|
+ /*
|
|
+ * Set state to Q_REQUEUE_PI_IN_PROGRESS unless an early wakeup has
|
|
+ * already set Q_REQUEUE_PI_IGNORE to signal that requeue should
|
|
+ * ignore the waiter.
|
|
+ */
|
|
+ old = atomic_read_acquire(&q->requeue_state);
|
|
+ do {
|
|
+ if (old == Q_REQUEUE_PI_IGNORE)
|
|
+ return false;
|
|
+
|
|
+ /*
|
|
+ * futex_proxy_trylock_atomic() might have set it to
|
|
+ * IN_PROGRESS and a interleaved early wake to WAIT.
|
|
+ *
|
|
+ * It was considered to have an extra state for that
|
|
+ * trylock, but that would just add more conditionals
|
|
+ * all over the place for a dubious value.
|
|
+ */
|
|
+ if (old != Q_REQUEUE_PI_NONE)
|
|
+ break;
|
|
+
|
|
+ new = Q_REQUEUE_PI_IN_PROGRESS;
|
|
+ } while (!atomic_try_cmpxchg(&q->requeue_state, &old, new));
|
|
+
|
|
+ q->pi_state = pi_state;
|
|
+ return true;
|
|
+}
|
|
+
|
|
+static inline void futex_requeue_pi_complete(struct futex_q *q, int locked)
|
|
+{
|
|
+ int old, new;
|
|
+
|
|
+ old = atomic_read_acquire(&q->requeue_state);
|
|
+ do {
|
|
+ if (old == Q_REQUEUE_PI_IGNORE)
|
|
+ return;
|
|
+
|
|
+ if (locked >= 0) {
|
|
+ /* Requeue succeeded. Set DONE or LOCKED */
|
|
+ WARN_ON_ONCE(old != Q_REQUEUE_PI_IN_PROGRESS &&
|
|
+ old != Q_REQUEUE_PI_WAIT);
|
|
+ new = Q_REQUEUE_PI_DONE + locked;
|
|
+ } else if (old == Q_REQUEUE_PI_IN_PROGRESS) {
|
|
+ /* Deadlock, no early wakeup interleave */
|
|
+ new = Q_REQUEUE_PI_NONE;
|
|
+ } else {
|
|
+ /* Deadlock, early wakeup interleave. */
|
|
+ WARN_ON_ONCE(old != Q_REQUEUE_PI_WAIT);
|
|
+ new = Q_REQUEUE_PI_IGNORE;
|
|
+ }
|
|
+ } while (!atomic_try_cmpxchg(&q->requeue_state, &old, new));
|
|
+
|
|
+#ifdef CONFIG_PREEMPT_RT
|
|
+ /* If the waiter interleaved with the requeue let it know */
|
|
+ if (unlikely(old == Q_REQUEUE_PI_WAIT))
|
|
+ rcuwait_wake_up(&q->requeue_wait);
|
|
+#endif
|
|
+}
|
|
+
|
|
+static inline int futex_requeue_pi_wakeup_sync(struct futex_q *q)
|
|
+{
|
|
+ int old, new;
|
|
+
|
|
+ old = atomic_read_acquire(&q->requeue_state);
|
|
+ do {
|
|
+ /* Is requeue done already? */
|
|
+ if (old >= Q_REQUEUE_PI_DONE)
|
|
+ return old;
|
|
+
|
|
+ /*
|
|
+ * If not done, then tell the requeue code to either ignore
|
|
+ * the waiter or to wake it up once the requeue is done.
|
|
+ */
|
|
+ new = Q_REQUEUE_PI_WAIT;
|
|
+ if (old == Q_REQUEUE_PI_NONE)
|
|
+ new = Q_REQUEUE_PI_IGNORE;
|
|
+ } while (!atomic_try_cmpxchg(&q->requeue_state, &old, new));
|
|
+
|
|
+ /* If the requeue was in progress, wait for it to complete */
|
|
+ if (old == Q_REQUEUE_PI_IN_PROGRESS) {
|
|
+#ifdef CONFIG_PREEMPT_RT
|
|
+ rcuwait_wait_event(&q->requeue_wait,
|
|
+ atomic_read(&q->requeue_state) != Q_REQUEUE_PI_WAIT,
|
|
+ TASK_UNINTERRUPTIBLE);
|
|
+#else
|
|
+ (void)atomic_cond_read_relaxed(&q->requeue_state, VAL != Q_REQUEUE_PI_WAIT);
|
|
+#endif
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * Requeue is now either prohibited or complete. Reread state
|
|
+ * because during the wait above it might have changed. Nothing
|
|
+ * will modify q->requeue_state after this point.
|
|
+ */
|
|
+ return atomic_read(&q->requeue_state);
|
|
+}
|
|
+
|
|
+/**
|
|
+ * requeue_pi_wake_futex() - Wake a task that acquired the lock during requeue
|
|
+ * @q: the futex_q
|
|
+ * @key: the key of the requeue target futex
|
|
+ * @hb: the hash_bucket of the requeue target futex
|
|
+ *
|
|
+ * During futex_requeue, with requeue_pi=1, it is possible to acquire the
|
|
+ * target futex if it is uncontended or via a lock steal.
|
|
+ *
|
|
+ * 1) Set @q::key to the requeue target futex key so the waiter can detect
|
|
+ * the wakeup on the right futex.
|
|
+ *
|
|
+ * 2) Dequeue @q from the hash bucket.
|
|
+ *
|
|
+ * 3) Set @q::rt_waiter to NULL so the woken up task can detect atomic lock
|
|
+ * acquisition.
|
|
+ *
|
|
+ * 4) Set the q->lock_ptr to the requeue target hb->lock for the case that
|
|
+ * the waiter has to fixup the pi state.
|
|
+ *
|
|
+ * 5) Complete the requeue state so the waiter can make progress. After
|
|
+ * this point the waiter task can return from the syscall immediately in
|
|
+ * case that the pi state does not have to be fixed up.
|
|
+ *
|
|
+ * 6) Wake the waiter task.
|
|
+ *
|
|
+ * Must be called with both q->lock_ptr and hb->lock held.
|
|
+ */
|
|
+static inline
|
|
+void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key,
|
|
+ struct futex_hash_bucket *hb)
|
|
+{
|
|
+ q->key = *key;
|
|
+
|
|
+ __futex_unqueue(q);
|
|
+
|
|
+ WARN_ON(!q->rt_waiter);
|
|
+ q->rt_waiter = NULL;
|
|
+
|
|
+ q->lock_ptr = &hb->lock;
|
|
+
|
|
+ /* Signal locked state to the waiter */
|
|
+ futex_requeue_pi_complete(q, 1);
|
|
+ wake_up_state(q->task, TASK_NORMAL);
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_proxy_trylock_atomic() - Attempt an atomic lock for the top waiter
|
|
+ * @pifutex: the user address of the to futex
|
|
+ * @hb1: the from futex hash bucket, must be locked by the caller
|
|
+ * @hb2: the to futex hash bucket, must be locked by the caller
|
|
+ * @key1: the from futex key
|
|
+ * @key2: the to futex key
|
|
+ * @ps: address to store the pi_state pointer
|
|
+ * @exiting: Pointer to store the task pointer of the owner task
|
|
+ * which is in the middle of exiting
|
|
+ * @set_waiters: force setting the FUTEX_WAITERS bit (1) or not (0)
|
|
+ *
|
|
+ * Try and get the lock on behalf of the top waiter if we can do it atomically.
|
|
+ * Wake the top waiter if we succeed. If the caller specified set_waiters,
|
|
+ * then direct futex_lock_pi_atomic() to force setting the FUTEX_WAITERS bit.
|
|
+ * hb1 and hb2 must be held by the caller.
|
|
+ *
|
|
+ * @exiting is only set when the return value is -EBUSY. If so, this holds
|
|
+ * a refcount on the exiting task on return and the caller needs to drop it
|
|
+ * after waiting for the exit to complete.
|
|
+ *
|
|
+ * Return:
|
|
+ * - 0 - failed to acquire the lock atomically;
|
|
+ * - >0 - acquired the lock, return value is vpid of the top_waiter
|
|
+ * - <0 - error
|
|
+ */
|
|
+static int
|
|
+futex_proxy_trylock_atomic(u32 __user *pifutex, struct futex_hash_bucket *hb1,
|
|
+ struct futex_hash_bucket *hb2, union futex_key *key1,
|
|
+ union futex_key *key2, struct futex_pi_state **ps,
|
|
+ struct task_struct **exiting, int set_waiters)
|
|
+{
|
|
+ struct futex_q *top_waiter = NULL;
|
|
+ u32 curval;
|
|
+ int ret;
|
|
+
|
|
+ if (futex_get_value_locked(&curval, pifutex))
|
|
+ return -EFAULT;
|
|
+
|
|
+ if (unlikely(should_fail_futex(true)))
|
|
+ return -EFAULT;
|
|
+
|
|
+ /*
|
|
+ * Find the top_waiter and determine if there are additional waiters.
|
|
+ * If the caller intends to requeue more than 1 waiter to pifutex,
|
|
+ * force futex_lock_pi_atomic() to set the FUTEX_WAITERS bit now,
|
|
+ * as we have means to handle the possible fault. If not, don't set
|
|
+ * the bit unnecessarily as it will force the subsequent unlock to enter
|
|
+ * the kernel.
|
|
+ */
|
|
+ top_waiter = futex_top_waiter(hb1, key1);
|
|
+
|
|
+ /* There are no waiters, nothing for us to do. */
|
|
+ if (!top_waiter)
|
|
+ return 0;
|
|
+
|
|
+ /*
|
|
+ * Ensure that this is a waiter sitting in futex_wait_requeue_pi()
|
|
+ * and waiting on the 'waitqueue' futex which is always !PI.
|
|
+ */
|
|
+ if (!top_waiter->rt_waiter || top_waiter->pi_state)
|
|
+ return -EINVAL;
|
|
+
|
|
+ /* Ensure we requeue to the expected futex. */
|
|
+ if (!futex_match(top_waiter->requeue_pi_key, key2))
|
|
+ return -EINVAL;
|
|
+
|
|
+ /* Ensure that this does not race against an early wakeup */
|
|
+ if (!futex_requeue_pi_prepare(top_waiter, NULL))
|
|
+ return -EAGAIN;
|
|
+
|
|
+ /*
|
|
+ * Try to take the lock for top_waiter and set the FUTEX_WAITERS bit
|
|
+ * in the contended case or if @set_waiters is true.
|
|
+ *
|
|
+ * In the contended case PI state is attached to the lock owner. If
|
|
+ * the user space lock can be acquired then PI state is attached to
|
|
+ * the new owner (@top_waiter->task) when @set_waiters is true.
|
|
+ */
|
|
+ ret = futex_lock_pi_atomic(pifutex, hb2, key2, ps, top_waiter->task,
|
|
+ exiting, set_waiters);
|
|
+ if (ret == 1) {
|
|
+ /*
|
|
+ * Lock was acquired in user space and PI state was
|
|
+ * attached to @top_waiter->task. That means state is fully
|
|
+ * consistent and the waiter can return to user space
|
|
+ * immediately after the wakeup.
|
|
+ */
|
|
+ requeue_pi_wake_futex(top_waiter, key2, hb2);
|
|
+ } else if (ret < 0) {
|
|
+ /* Rewind top_waiter::requeue_state */
|
|
+ futex_requeue_pi_complete(top_waiter, ret);
|
|
+ } else {
|
|
+ /*
|
|
+ * futex_lock_pi_atomic() did not acquire the user space
|
|
+ * futex, but managed to establish the proxy lock and pi
|
|
+ * state. top_waiter::requeue_state cannot be fixed up here
|
|
+ * because the waiter is not enqueued on the rtmutex
|
|
+ * yet. This is handled at the callsite depending on the
|
|
+ * result of rt_mutex_start_proxy_lock() which is
|
|
+ * guaranteed to be reached with this function returning 0.
|
|
+ */
|
|
+ }
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_requeue() - Requeue waiters from uaddr1 to uaddr2
|
|
+ * @uaddr1: source futex user address
|
|
+ * @flags: futex flags (FLAGS_SHARED, etc.)
|
|
+ * @uaddr2: target futex user address
|
|
+ * @nr_wake: number of waiters to wake (must be 1 for requeue_pi)
|
|
+ * @nr_requeue: number of waiters to requeue (0-INT_MAX)
|
|
+ * @cmpval: @uaddr1 expected value (or %NULL)
|
|
+ * @requeue_pi: if we are attempting to requeue from a non-pi futex to a
|
|
+ * pi futex (pi to pi requeue is not supported)
|
|
+ *
|
|
+ * Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire
|
|
+ * uaddr2 atomically on behalf of the top waiter.
|
|
+ *
|
|
+ * Return:
|
|
+ * - >=0 - on success, the number of tasks requeued or woken;
|
|
+ * - <0 - on error
|
|
+ */
|
|
+int futex_requeue(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2,
|
|
+ int nr_wake, int nr_requeue, u32 *cmpval, int requeue_pi)
|
|
+{
|
|
+ union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
|
|
+ int task_count = 0, ret;
|
|
+ struct futex_pi_state *pi_state = NULL;
|
|
+ struct futex_hash_bucket *hb1, *hb2;
|
|
+ struct futex_q *this, *next;
|
|
+ DEFINE_WAKE_Q(wake_q);
|
|
+
|
|
+ if (nr_wake < 0 || nr_requeue < 0)
|
|
+ return -EINVAL;
|
|
+
|
|
+ /*
|
|
+ * When PI not supported: return -ENOSYS if requeue_pi is true,
|
|
+ * consequently the compiler knows requeue_pi is always false past
|
|
+ * this point which will optimize away all the conditional code
|
|
+ * further down.
|
|
+ */
|
|
+ if (!IS_ENABLED(CONFIG_FUTEX_PI) && requeue_pi)
|
|
+ return -ENOSYS;
|
|
+
|
|
+ if (requeue_pi) {
|
|
+ /*
|
|
+ * Requeue PI only works on two distinct uaddrs. This
|
|
+ * check is only valid for private futexes. See below.
|
|
+ */
|
|
+ if (uaddr1 == uaddr2)
|
|
+ return -EINVAL;
|
|
+
|
|
+ /*
|
|
+ * futex_requeue() allows the caller to define the number
|
|
+ * of waiters to wake up via the @nr_wake argument. With
|
|
+ * REQUEUE_PI, waking up more than one waiter is creating
|
|
+ * more problems than it solves. Waking up a waiter makes
|
|
+ * only sense if the PI futex @uaddr2 is uncontended as
|
|
+ * this allows the requeue code to acquire the futex
|
|
+ * @uaddr2 before waking the waiter. The waiter can then
|
|
+ * return to user space without further action. A secondary
|
|
+ * wakeup would just make the futex_wait_requeue_pi()
|
|
+ * handling more complex, because that code would have to
|
|
+ * look up pi_state and do more or less all the handling
|
|
+ * which the requeue code has to do for the to be requeued
|
|
+ * waiters. So restrict the number of waiters to wake to
|
|
+ * one, and only wake it up when the PI futex is
|
|
+ * uncontended. Otherwise requeue it and let the unlock of
|
|
+ * the PI futex handle the wakeup.
|
|
+ *
|
|
+ * All REQUEUE_PI users, e.g. pthread_cond_signal() and
|
|
+ * pthread_cond_broadcast() must use nr_wake=1.
|
|
+ */
|
|
+ if (nr_wake != 1)
|
|
+ return -EINVAL;
|
|
+
|
|
+ /*
|
|
+ * requeue_pi requires a pi_state, try to allocate it now
|
|
+ * without any locks in case it fails.
|
|
+ */
|
|
+ if (refill_pi_state_cache())
|
|
+ return -ENOMEM;
|
|
+ }
|
|
+
|
|
+retry:
|
|
+ ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, FUTEX_READ);
|
|
+ if (unlikely(ret != 0))
|
|
+ return ret;
|
|
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2,
|
|
+ requeue_pi ? FUTEX_WRITE : FUTEX_READ);
|
|
+ if (unlikely(ret != 0))
|
|
+ return ret;
|
|
+
|
|
+ /*
|
|
+ * The check above which compares uaddrs is not sufficient for
|
|
+ * shared futexes. We need to compare the keys:
|
|
+ */
|
|
+ if (requeue_pi && futex_match(&key1, &key2))
|
|
+ return -EINVAL;
|
|
+
|
|
+ hb1 = futex_hash(&key1);
|
|
+ hb2 = futex_hash(&key2);
|
|
+
|
|
+retry_private:
|
|
+ futex_hb_waiters_inc(hb2);
|
|
+ double_lock_hb(hb1, hb2);
|
|
+
|
|
+ if (likely(cmpval != NULL)) {
|
|
+ u32 curval;
|
|
+
|
|
+ ret = futex_get_value_locked(&curval, uaddr1);
|
|
+
|
|
+ if (unlikely(ret)) {
|
|
+ double_unlock_hb(hb1, hb2);
|
|
+ futex_hb_waiters_dec(hb2);
|
|
+
|
|
+ ret = get_user(curval, uaddr1);
|
|
+ if (ret)
|
|
+ return ret;
|
|
+
|
|
+ if (!(flags & FLAGS_SHARED))
|
|
+ goto retry_private;
|
|
+
|
|
+ goto retry;
|
|
+ }
|
|
+ if (curval != *cmpval) {
|
|
+ ret = -EAGAIN;
|
|
+ goto out_unlock;
|
|
+ }
|
|
+ }
|
|
+
|
|
+ if (requeue_pi) {
|
|
+ struct task_struct *exiting = NULL;
|
|
+
|
|
+ /*
|
|
+ * Attempt to acquire uaddr2 and wake the top waiter. If we
|
|
+ * intend to requeue waiters, force setting the FUTEX_WAITERS
|
|
+ * bit. We force this here where we are able to easily handle
|
|
+ * faults rather in the requeue loop below.
|
|
+ *
|
|
+ * Updates topwaiter::requeue_state if a top waiter exists.
|
|
+ */
|
|
+ ret = futex_proxy_trylock_atomic(uaddr2, hb1, hb2, &key1,
|
|
+ &key2, &pi_state,
|
|
+ &exiting, nr_requeue);
|
|
+
|
|
+ /*
|
|
+ * At this point the top_waiter has either taken uaddr2 or
|
|
+ * is waiting on it. In both cases pi_state has been
|
|
+ * established and an initial refcount on it. In case of an
|
|
+ * error there's nothing.
|
|
+ *
|
|
+ * The top waiter's requeue_state is up to date:
|
|
+ *
|
|
+ * - If the lock was acquired atomically (ret == 1), then
|
|
+ * the state is Q_REQUEUE_PI_LOCKED.
|
|
+ *
|
|
+ * The top waiter has been dequeued and woken up and can
|
|
+ * return to user space immediately. The kernel/user
|
|
+ * space state is consistent. In case that there must be
|
|
+ * more waiters requeued the WAITERS bit in the user
|
|
+ * space futex is set so the top waiter task has to go
|
|
+ * into the syscall slowpath to unlock the futex. This
|
|
+ * will block until this requeue operation has been
|
|
+ * completed and the hash bucket locks have been
|
|
+ * dropped.
|
|
+ *
|
|
+ * - If the trylock failed with an error (ret < 0) then
|
|
+ * the state is either Q_REQUEUE_PI_NONE, i.e. "nothing
|
|
+ * happened", or Q_REQUEUE_PI_IGNORE when there was an
|
|
+ * interleaved early wakeup.
|
|
+ *
|
|
+ * - If the trylock did not succeed (ret == 0) then the
|
|
+ * state is either Q_REQUEUE_PI_IN_PROGRESS or
|
|
+ * Q_REQUEUE_PI_WAIT if an early wakeup interleaved.
|
|
+ * This will be cleaned up in the loop below, which
|
|
+ * cannot fail because futex_proxy_trylock_atomic() did
|
|
+ * the same sanity checks for requeue_pi as the loop
|
|
+ * below does.
|
|
+ */
|
|
+ switch (ret) {
|
|
+ case 0:
|
|
+ /* We hold a reference on the pi state. */
|
|
+ break;
|
|
+
|
|
+ case 1:
|
|
+ /*
|
|
+ * futex_proxy_trylock_atomic() acquired the user space
|
|
+ * futex. Adjust task_count.
|
|
+ */
|
|
+ task_count++;
|
|
+ ret = 0;
|
|
+ break;
|
|
+
|
|
+ /*
|
|
+ * If the above failed, then pi_state is NULL and
|
|
+ * waiter::requeue_state is correct.
|
|
+ */
|
|
+ case -EFAULT:
|
|
+ double_unlock_hb(hb1, hb2);
|
|
+ futex_hb_waiters_dec(hb2);
|
|
+ ret = fault_in_user_writeable(uaddr2);
|
|
+ if (!ret)
|
|
+ goto retry;
|
|
+ return ret;
|
|
+ case -EBUSY:
|
|
+ case -EAGAIN:
|
|
+ /*
|
|
+ * Two reasons for this:
|
|
+ * - EBUSY: Owner is exiting and we just wait for the
|
|
+ * exit to complete.
|
|
+ * - EAGAIN: The user space value changed.
|
|
+ */
|
|
+ double_unlock_hb(hb1, hb2);
|
|
+ futex_hb_waiters_dec(hb2);
|
|
+ /*
|
|
+ * Handle the case where the owner is in the middle of
|
|
+ * exiting. Wait for the exit to complete otherwise
|
|
+ * this task might loop forever, aka. live lock.
|
|
+ */
|
|
+ wait_for_owner_exiting(ret, exiting);
|
|
+ cond_resched();
|
|
+ goto retry;
|
|
+ default:
|
|
+ goto out_unlock;
|
|
+ }
|
|
+ }
|
|
+
|
|
+ plist_for_each_entry_safe(this, next, &hb1->chain, list) {
|
|
+ if (task_count - nr_wake >= nr_requeue)
|
|
+ break;
|
|
+
|
|
+ if (!futex_match(&this->key, &key1))
|
|
+ continue;
|
|
+
|
|
+ /*
|
|
+ * FUTEX_WAIT_REQUEUE_PI and FUTEX_CMP_REQUEUE_PI should always
|
|
+ * be paired with each other and no other futex ops.
|
|
+ *
|
|
+ * We should never be requeueing a futex_q with a pi_state,
|
|
+ * which is awaiting a futex_unlock_pi().
|
|
+ */
|
|
+ if ((requeue_pi && !this->rt_waiter) ||
|
|
+ (!requeue_pi && this->rt_waiter) ||
|
|
+ this->pi_state) {
|
|
+ ret = -EINVAL;
|
|
+ break;
|
|
+ }
|
|
+
|
|
+ /* Plain futexes just wake or requeue and are done */
|
|
+ if (!requeue_pi) {
|
|
+ if (++task_count <= nr_wake)
|
|
+ futex_wake_mark(&wake_q, this);
|
|
+ else
|
|
+ requeue_futex(this, hb1, hb2, &key2);
|
|
+ continue;
|
|
+ }
|
|
+
|
|
+ /* Ensure we requeue to the expected futex for requeue_pi. */
|
|
+ if (!futex_match(this->requeue_pi_key, &key2)) {
|
|
+ ret = -EINVAL;
|
|
+ break;
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * Requeue nr_requeue waiters and possibly one more in the case
|
|
+ * of requeue_pi if we couldn't acquire the lock atomically.
|
|
+ *
|
|
+ * Prepare the waiter to take the rt_mutex. Take a refcount
|
|
+ * on the pi_state and store the pointer in the futex_q
|
|
+ * object of the waiter.
|
|
+ */
|
|
+ get_pi_state(pi_state);
|
|
+
|
|
+ /* Don't requeue when the waiter is already on the way out. */
|
|
+ if (!futex_requeue_pi_prepare(this, pi_state)) {
|
|
+ /*
|
|
+ * Early woken waiter signaled that it is on the
|
|
+ * way out. Drop the pi_state reference and try the
|
|
+ * next waiter. @this->pi_state is still NULL.
|
|
+ */
|
|
+ put_pi_state(pi_state);
|
|
+ continue;
|
|
+ }
|
|
+
|
|
+ ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex,
|
|
+ this->rt_waiter,
|
|
+ this->task);
|
|
+
|
|
+ if (ret == 1) {
|
|
+ /*
|
|
+ * We got the lock. We do neither drop the refcount
|
|
+ * on pi_state nor clear this->pi_state because the
|
|
+ * waiter needs the pi_state for cleaning up the
|
|
+ * user space value. It will drop the refcount
|
|
+ * after doing so. this::requeue_state is updated
|
|
+ * in the wakeup as well.
|
|
+ */
|
|
+ requeue_pi_wake_futex(this, &key2, hb2);
|
|
+ task_count++;
|
|
+ } else if (!ret) {
|
|
+ /* Waiter is queued, move it to hb2 */
|
|
+ requeue_futex(this, hb1, hb2, &key2);
|
|
+ futex_requeue_pi_complete(this, 0);
|
|
+ task_count++;
|
|
+ } else {
|
|
+ /*
|
|
+ * rt_mutex_start_proxy_lock() detected a potential
|
|
+ * deadlock when we tried to queue that waiter.
|
|
+ * Drop the pi_state reference which we took above
|
|
+ * and remove the pointer to the state from the
|
|
+ * waiters futex_q object.
|
|
+ */
|
|
+ this->pi_state = NULL;
|
|
+ put_pi_state(pi_state);
|
|
+ futex_requeue_pi_complete(this, ret);
|
|
+ /*
|
|
+ * We stop queueing more waiters and let user space
|
|
+ * deal with the mess.
|
|
+ */
|
|
+ break;
|
|
+ }
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * We took an extra initial reference to the pi_state in
|
|
+ * futex_proxy_trylock_atomic(). We need to drop it here again.
|
|
+ */
|
|
+ put_pi_state(pi_state);
|
|
+
|
|
+out_unlock:
|
|
+ double_unlock_hb(hb1, hb2);
|
|
+ wake_up_q(&wake_q);
|
|
+ futex_hb_waiters_dec(hb2);
|
|
+ return ret ? ret : task_count;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * handle_early_requeue_pi_wakeup() - Handle early wakeup on the initial futex
|
|
+ * @hb: the hash_bucket futex_q was original enqueued on
|
|
+ * @q: the futex_q woken while waiting to be requeued
|
|
+ * @timeout: the timeout associated with the wait (NULL if none)
|
|
+ *
|
|
+ * Determine the cause for the early wakeup.
|
|
+ *
|
|
+ * Return:
|
|
+ * -EWOULDBLOCK or -ETIMEDOUT or -ERESTARTNOINTR
|
|
+ */
|
|
+static inline
|
|
+int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
|
|
+ struct futex_q *q,
|
|
+ struct hrtimer_sleeper *timeout)
|
|
+{
|
|
+ int ret;
|
|
+
|
|
+ /*
|
|
+ * With the hb lock held, we avoid races while we process the wakeup.
|
|
+ * We only need to hold hb (and not hb2) to ensure atomicity as the
|
|
+ * wakeup code can't change q.key from uaddr to uaddr2 if we hold hb.
|
|
+ * It can't be requeued from uaddr2 to something else since we don't
|
|
+ * support a PI aware source futex for requeue.
|
|
+ */
|
|
+ WARN_ON_ONCE(&hb->lock != q->lock_ptr);
|
|
+
|
|
+ /*
|
|
+ * We were woken prior to requeue by a timeout or a signal.
|
|
+ * Unqueue the futex_q and determine which it was.
|
|
+ */
|
|
+ plist_del(&q->list, &hb->chain);
|
|
+ futex_hb_waiters_dec(hb);
|
|
+
|
|
+ /* Handle spurious wakeups gracefully */
|
|
+ ret = -EWOULDBLOCK;
|
|
+ if (timeout && !timeout->task)
|
|
+ ret = -ETIMEDOUT;
|
|
+ else if (signal_pending(current))
|
|
+ ret = -ERESTARTNOINTR;
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_wait_requeue_pi() - Wait on uaddr and take uaddr2
|
|
+ * @uaddr: the futex we initially wait on (non-pi)
|
|
+ * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, etc.), they must be
|
|
+ * the same type, no requeueing from private to shared, etc.
|
|
+ * @val: the expected value of uaddr
|
|
+ * @abs_time: absolute timeout
|
|
+ * @bitset: 32 bit wakeup bitset set by userspace, defaults to all
|
|
+ * @uaddr2: the pi futex we will take prior to returning to user-space
|
|
+ *
|
|
+ * The caller will wait on uaddr and will be requeued by futex_requeue() to
|
|
+ * uaddr2 which must be PI aware and unique from uaddr. Normal wakeup will wake
|
|
+ * on uaddr2 and complete the acquisition of the rt_mutex prior to returning to
|
|
+ * userspace. This ensures the rt_mutex maintains an owner when it has waiters;
|
|
+ * without one, the pi logic would not know which task to boost/deboost, if
|
|
+ * there was a need to.
|
|
+ *
|
|
+ * We call schedule in futex_wait_queue() when we enqueue and return there
|
|
+ * via the following--
|
|
+ * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue()
|
|
+ * 2) wakeup on uaddr2 after a requeue
|
|
+ * 3) signal
|
|
+ * 4) timeout
|
|
+ *
|
|
+ * If 3, cleanup and return -ERESTARTNOINTR.
|
|
+ *
|
|
+ * If 2, we may then block on trying to take the rt_mutex and return via:
|
|
+ * 5) successful lock
|
|
+ * 6) signal
|
|
+ * 7) timeout
|
|
+ * 8) other lock acquisition failure
|
|
+ *
|
|
+ * If 6, return -EWOULDBLOCK (restarting the syscall would do the same).
|
|
+ *
|
|
+ * If 4 or 7, we cleanup and return with -ETIMEDOUT.
|
|
+ *
|
|
+ * Return:
|
|
+ * - 0 - On success;
|
|
+ * - <0 - On error
|
|
+ */
|
|
+int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
|
|
+ u32 val, ktime_t *abs_time, u32 bitset,
|
|
+ u32 __user *uaddr2)
|
|
+{
|
|
+ struct hrtimer_sleeper timeout, *to;
|
|
+ struct rt_mutex_waiter rt_waiter;
|
|
+ struct futex_hash_bucket *hb;
|
|
+ union futex_key key2 = FUTEX_KEY_INIT;
|
|
+ struct futex_q q = futex_q_init;
|
|
+ struct rt_mutex_base *pi_mutex;
|
|
+ int res, ret;
|
|
+
|
|
+ if (!IS_ENABLED(CONFIG_FUTEX_PI))
|
|
+ return -ENOSYS;
|
|
+
|
|
+ if (uaddr == uaddr2)
|
|
+ return -EINVAL;
|
|
+
|
|
+ if (!bitset)
|
|
+ return -EINVAL;
|
|
+
|
|
+ to = futex_setup_timer(abs_time, &timeout, flags,
|
|
+ current->timer_slack_ns);
|
|
+
|
|
+ /*
|
|
+ * The waiter is allocated on our stack, manipulated by the requeue
|
|
+ * code while we sleep on uaddr.
|
|
+ */
|
|
+ rt_mutex_init_waiter(&rt_waiter);
|
|
+
|
|
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, FUTEX_WRITE);
|
|
+ if (unlikely(ret != 0))
|
|
+ goto out;
|
|
+
|
|
+ q.bitset = bitset;
|
|
+ q.rt_waiter = &rt_waiter;
|
|
+ q.requeue_pi_key = &key2;
|
|
+
|
|
+ /*
|
|
+ * Prepare to wait on uaddr. On success, it holds hb->lock and q
|
|
+ * is initialized.
|
|
+ */
|
|
+ ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
|
|
+ if (ret)
|
|
+ goto out;
|
|
+
|
|
+ /*
|
|
+ * The check above which compares uaddrs is not sufficient for
|
|
+ * shared futexes. We need to compare the keys:
|
|
+ */
|
|
+ if (futex_match(&q.key, &key2)) {
|
|
+ futex_q_unlock(hb);
|
|
+ ret = -EINVAL;
|
|
+ goto out;
|
|
+ }
|
|
+
|
|
+ /* Queue the futex_q, drop the hb lock, wait for wakeup. */
|
|
+ futex_wait_queue(hb, &q, to);
|
|
+
|
|
+ switch (futex_requeue_pi_wakeup_sync(&q)) {
|
|
+ case Q_REQUEUE_PI_IGNORE:
|
|
+ /* The waiter is still on uaddr1 */
|
|
+ spin_lock(&hb->lock);
|
|
+ ret = handle_early_requeue_pi_wakeup(hb, &q, to);
|
|
+ spin_unlock(&hb->lock);
|
|
+ break;
|
|
+
|
|
+ case Q_REQUEUE_PI_LOCKED:
|
|
+ /* The requeue acquired the lock */
|
|
+ if (q.pi_state && (q.pi_state->owner != current)) {
|
|
+ spin_lock(q.lock_ptr);
|
|
+ ret = fixup_pi_owner(uaddr2, &q, true);
|
|
+ /*
|
|
+ * Drop the reference to the pi state which the
|
|
+ * requeue_pi() code acquired for us.
|
|
+ */
|
|
+ put_pi_state(q.pi_state);
|
|
+ spin_unlock(q.lock_ptr);
|
|
+ /*
|
|
+ * Adjust the return value. It's either -EFAULT or
|
|
+ * success (1) but the caller expects 0 for success.
|
|
+ */
|
|
+ ret = ret < 0 ? ret : 0;
|
|
+ }
|
|
+ break;
|
|
+
|
|
+ case Q_REQUEUE_PI_DONE:
|
|
+ /* Requeue completed. Current is 'pi_blocked_on' the rtmutex */
|
|
+ pi_mutex = &q.pi_state->pi_mutex;
|
|
+ ret = rt_mutex_wait_proxy_lock(pi_mutex, to, &rt_waiter);
|
|
+
|
|
+ /* Current is not longer pi_blocked_on */
|
|
+ spin_lock(q.lock_ptr);
|
|
+ if (ret && !rt_mutex_cleanup_proxy_lock(pi_mutex, &rt_waiter))
|
|
+ ret = 0;
|
|
+
|
|
+ debug_rt_mutex_free_waiter(&rt_waiter);
|
|
+ /*
|
|
+ * Fixup the pi_state owner and possibly acquire the lock if we
|
|
+ * haven't already.
|
|
+ */
|
|
+ res = fixup_pi_owner(uaddr2, &q, !ret);
|
|
+ /*
|
|
+ * If fixup_pi_owner() returned an error, propagate that. If it
|
|
+ * acquired the lock, clear -ETIMEDOUT or -EINTR.
|
|
+ */
|
|
+ if (res)
|
|
+ ret = (res < 0) ? res : 0;
|
|
+
|
|
+ futex_unqueue_pi(&q);
|
|
+ spin_unlock(q.lock_ptr);
|
|
+
|
|
+ if (ret == -EINTR) {
|
|
+ /*
|
|
+ * We've already been requeued, but cannot restart
|
|
+ * by calling futex_lock_pi() directly. We could
|
|
+ * restart this syscall, but it would detect that
|
|
+ * the user space "val" changed and return
|
|
+ * -EWOULDBLOCK. Save the overhead of the restart
|
|
+ * and return -EWOULDBLOCK directly.
|
|
+ */
|
|
+ ret = -EWOULDBLOCK;
|
|
+ }
|
|
+ break;
|
|
+ default:
|
|
+ BUG();
|
|
+ }
|
|
+
|
|
+out:
|
|
+ if (to) {
|
|
+ hrtimer_cancel(&to->timer);
|
|
+ destroy_hrtimer_on_stack(&to->timer);
|
|
+ }
|
|
+ return ret;
|
|
+}
|
|
+
|
|
diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c
|
|
new file mode 100644
|
|
index 000000000..368e9c17f
|
|
--- /dev/null
|
|
+++ b/kernel/futex/syscalls.c
|
|
@@ -0,0 +1,396 @@
|
|
+// SPDX-License-Identifier: GPL-2.0-or-later
|
|
+
|
|
+#include <linux/compat.h>
|
|
+#include <linux/syscalls.h>
|
|
+#include <linux/time_namespace.h>
|
|
+
|
|
+#include "futex.h"
|
|
+
|
|
+/*
|
|
+ * Support for robust futexes: the kernel cleans up held futexes at
|
|
+ * thread exit time.
|
|
+ *
|
|
+ * Implementation: user-space maintains a per-thread list of locks it
|
|
+ * is holding. Upon do_exit(), the kernel carefully walks this list,
|
|
+ * and marks all locks that are owned by this thread with the
|
|
+ * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
|
|
+ * always manipulated with the lock held, so the list is private and
|
|
+ * per-thread. Userspace also maintains a per-thread 'list_op_pending'
|
|
+ * field, to allow the kernel to clean up if the thread dies after
|
|
+ * acquiring the lock, but just before it could have added itself to
|
|
+ * the list. There can only be one such pending lock.
|
|
+ */
|
|
+
|
|
+/**
|
|
+ * sys_set_robust_list() - Set the robust-futex list head of a task
|
|
+ * @head: pointer to the list-head
|
|
+ * @len: length of the list-head, as userspace expects
|
|
+ */
|
|
+SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
|
|
+ size_t, len)
|
|
+{
|
|
+ if (!futex_cmpxchg_enabled)
|
|
+ return -ENOSYS;
|
|
+ /*
|
|
+ * The kernel knows only one size for now:
|
|
+ */
|
|
+ if (unlikely(len != sizeof(*head)))
|
|
+ return -EINVAL;
|
|
+
|
|
+ current->robust_list = head;
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * sys_get_robust_list() - Get the robust-futex list head of a task
|
|
+ * @pid: pid of the process [zero for current task]
|
|
+ * @head_ptr: pointer to a list-head pointer, the kernel fills it in
|
|
+ * @len_ptr: pointer to a length field, the kernel fills in the header size
|
|
+ */
|
|
+SYSCALL_DEFINE3(get_robust_list, int, pid,
|
|
+ struct robust_list_head __user * __user *, head_ptr,
|
|
+ size_t __user *, len_ptr)
|
|
+{
|
|
+ struct robust_list_head __user *head;
|
|
+ unsigned long ret;
|
|
+ struct task_struct *p;
|
|
+
|
|
+ if (!futex_cmpxchg_enabled)
|
|
+ return -ENOSYS;
|
|
+
|
|
+ rcu_read_lock();
|
|
+
|
|
+ ret = -ESRCH;
|
|
+ if (!pid)
|
|
+ p = current;
|
|
+ else {
|
|
+ p = find_task_by_vpid(pid);
|
|
+ if (!p)
|
|
+ goto err_unlock;
|
|
+ }
|
|
+
|
|
+ ret = -EPERM;
|
|
+ if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
|
|
+ goto err_unlock;
|
|
+
|
|
+ head = p->robust_list;
|
|
+ rcu_read_unlock();
|
|
+
|
|
+ if (put_user(sizeof(*head), len_ptr))
|
|
+ return -EFAULT;
|
|
+ return put_user(head, head_ptr);
|
|
+
|
|
+err_unlock:
|
|
+ rcu_read_unlock();
|
|
+
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
|
|
+ u32 __user *uaddr2, u32 val2, u32 val3)
|
|
+{
|
|
+ int cmd = op & FUTEX_CMD_MASK;
|
|
+ unsigned int flags = 0;
|
|
+
|
|
+ if (!(op & FUTEX_PRIVATE_FLAG))
|
|
+ flags |= FLAGS_SHARED;
|
|
+
|
|
+ if (op & FUTEX_CLOCK_REALTIME) {
|
|
+ flags |= FLAGS_CLOCKRT;
|
|
+ if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI &&
|
|
+ cmd != FUTEX_LOCK_PI2)
|
|
+ return -ENOSYS;
|
|
+ }
|
|
+
|
|
+ switch (cmd) {
|
|
+ case FUTEX_LOCK_PI:
|
|
+ case FUTEX_LOCK_PI2:
|
|
+ case FUTEX_UNLOCK_PI:
|
|
+ case FUTEX_TRYLOCK_PI:
|
|
+ case FUTEX_WAIT_REQUEUE_PI:
|
|
+ case FUTEX_CMP_REQUEUE_PI:
|
|
+ if (!futex_cmpxchg_enabled)
|
|
+ return -ENOSYS;
|
|
+ }
|
|
+
|
|
+ switch (cmd) {
|
|
+ case FUTEX_WAIT:
|
|
+ val3 = FUTEX_BITSET_MATCH_ANY;
|
|
+ fallthrough;
|
|
+ case FUTEX_WAIT_BITSET:
|
|
+ return futex_wait(uaddr, flags, val, timeout, val3);
|
|
+ case FUTEX_WAKE:
|
|
+ val3 = FUTEX_BITSET_MATCH_ANY;
|
|
+ fallthrough;
|
|
+ case FUTEX_WAKE_BITSET:
|
|
+ return futex_wake(uaddr, flags, val, val3);
|
|
+ case FUTEX_REQUEUE:
|
|
+ return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
|
|
+ case FUTEX_CMP_REQUEUE:
|
|
+ return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
|
|
+ case FUTEX_WAKE_OP:
|
|
+ return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
|
|
+ case FUTEX_LOCK_PI:
|
|
+ flags |= FLAGS_CLOCKRT;
|
|
+ fallthrough;
|
|
+ case FUTEX_LOCK_PI2:
|
|
+ return futex_lock_pi(uaddr, flags, timeout, 0);
|
|
+ case FUTEX_UNLOCK_PI:
|
|
+ return futex_unlock_pi(uaddr, flags);
|
|
+ case FUTEX_TRYLOCK_PI:
|
|
+ return futex_lock_pi(uaddr, flags, NULL, 1);
|
|
+ case FUTEX_WAIT_REQUEUE_PI:
|
|
+ val3 = FUTEX_BITSET_MATCH_ANY;
|
|
+ return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
|
|
+ uaddr2);
|
|
+ case FUTEX_CMP_REQUEUE_PI:
|
|
+ return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
|
|
+ }
|
|
+ return -ENOSYS;
|
|
+}
|
|
+
|
|
+static __always_inline bool futex_cmd_has_timeout(u32 cmd)
|
|
+{
|
|
+ switch (cmd) {
|
|
+ case FUTEX_WAIT:
|
|
+ case FUTEX_LOCK_PI:
|
|
+ case FUTEX_LOCK_PI2:
|
|
+ case FUTEX_WAIT_BITSET:
|
|
+ case FUTEX_WAIT_REQUEUE_PI:
|
|
+ return true;
|
|
+ }
|
|
+ return false;
|
|
+}
|
|
+
|
|
+static __always_inline int
|
|
+futex_init_timeout(u32 cmd, u32 op, struct timespec64 *ts, ktime_t *t)
|
|
+{
|
|
+ if (!timespec64_valid(ts))
|
|
+ return -EINVAL;
|
|
+
|
|
+ *t = timespec64_to_ktime(*ts);
|
|
+ if (cmd == FUTEX_WAIT)
|
|
+ *t = ktime_add_safe(ktime_get(), *t);
|
|
+ else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
|
|
+ *t = timens_ktime_to_host(CLOCK_MONOTONIC, *t);
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
|
|
+ const struct __kernel_timespec __user *, utime,
|
|
+ u32 __user *, uaddr2, u32, val3)
|
|
+{
|
|
+ int ret, cmd = op & FUTEX_CMD_MASK;
|
|
+ ktime_t t, *tp = NULL;
|
|
+ struct timespec64 ts;
|
|
+
|
|
+ if (utime && futex_cmd_has_timeout(cmd)) {
|
|
+ if (unlikely(should_fail_futex(!(op & FUTEX_PRIVATE_FLAG))))
|
|
+ return -EFAULT;
|
|
+ if (get_timespec64(&ts, utime))
|
|
+ return -EFAULT;
|
|
+ ret = futex_init_timeout(cmd, op, &ts, &t);
|
|
+ if (ret)
|
|
+ return ret;
|
|
+ tp = &t;
|
|
+ }
|
|
+
|
|
+ return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
|
|
+}
|
|
+
|
|
+/* Mask of available flags for each futex in futex_waitv list */
|
|
+#define FUTEXV_WAITER_MASK (FUTEX_32 | FUTEX_PRIVATE_FLAG)
|
|
+
|
|
+/**
|
|
+ * futex_parse_waitv - Parse a waitv array from userspace
|
|
+ * @futexv: Kernel side list of waiters to be filled
|
|
+ * @uwaitv: Userspace list to be parsed
|
|
+ * @nr_futexes: Length of futexv
|
|
+ *
|
|
+ * Return: Error code on failure, 0 on success
|
|
+ */
|
|
+static int futex_parse_waitv(struct futex_vector *futexv,
|
|
+ struct futex_waitv __user *uwaitv,
|
|
+ unsigned int nr_futexes)
|
|
+{
|
|
+ struct futex_waitv aux;
|
|
+ unsigned int i;
|
|
+
|
|
+ for (i = 0; i < nr_futexes; i++) {
|
|
+ if (copy_from_user(&aux, &uwaitv[i], sizeof(aux)))
|
|
+ return -EFAULT;
|
|
+
|
|
+ if ((aux.flags & ~FUTEXV_WAITER_MASK) || aux.__reserved)
|
|
+ return -EINVAL;
|
|
+
|
|
+ if (!(aux.flags & FUTEX_32))
|
|
+ return -EINVAL;
|
|
+
|
|
+ futexv[i].w.flags = aux.flags;
|
|
+ futexv[i].w.val = aux.val;
|
|
+ futexv[i].w.uaddr = aux.uaddr;
|
|
+ futexv[i].q = futex_q_init;
|
|
+ }
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * sys_futex_waitv - Wait on a list of futexes
|
|
+ * @waiters: List of futexes to wait on
|
|
+ * @nr_futexes: Length of futexv
|
|
+ * @flags: Flag for timeout (monotonic/realtime)
|
|
+ * @timeout: Optional absolute timeout.
|
|
+ * @clockid: Clock to be used for the timeout, realtime or monotonic.
|
|
+ *
|
|
+ * Given an array of `struct futex_waitv`, wait on each uaddr. The thread wakes
|
|
+ * if a futex_wake() is performed at any uaddr. The syscall returns immediately
|
|
+ * if any waiter has *uaddr != val. *timeout is an optional timeout value for the
|
|
+ * operation. Each waiter has individual flags. The `flags` argument for the
|
|
+ * syscall should be used solely for specifying the timeout as realtime, if
|
|
+ * needed. Flags for private futexes, sizes, etc. should be used on the
|
|
+ * individual flags of each waiter.
|
|
+ *
|
|
+ * Returns the array index of one of the awaken futexes. There's no given
|
|
+ * information of how many were awakened, or any particular attribute of it (if
|
|
+ * it's the first awakened, if it is of the smaller index...).
|
|
+ */
|
|
+
|
|
+SYSCALL_DEFINE5(futex_waitv, struct futex_waitv __user *, waiters,
|
|
+ unsigned int, nr_futexes, unsigned int, flags,
|
|
+ struct __kernel_timespec __user *, timeout, clockid_t, clockid)
|
|
+{
|
|
+ struct hrtimer_sleeper to;
|
|
+ struct futex_vector *futexv;
|
|
+ struct timespec64 ts;
|
|
+ ktime_t time;
|
|
+ int ret;
|
|
+
|
|
+ /* This syscall supports no flags for now */
|
|
+ if (flags)
|
|
+ return -EINVAL;
|
|
+
|
|
+ if (!nr_futexes || nr_futexes > FUTEX_WAITV_MAX || !waiters)
|
|
+ return -EINVAL;
|
|
+
|
|
+ if (timeout) {
|
|
+ int flag_clkid = 0, flag_init = 0;
|
|
+
|
|
+ if (clockid == CLOCK_REALTIME) {
|
|
+ flag_clkid = FLAGS_CLOCKRT;
|
|
+ flag_init = FUTEX_CLOCK_REALTIME;
|
|
+ }
|
|
+
|
|
+ if (clockid != CLOCK_REALTIME && clockid != CLOCK_MONOTONIC)
|
|
+ return -EINVAL;
|
|
+
|
|
+ if (get_timespec64(&ts, timeout))
|
|
+ return -EFAULT;
|
|
+
|
|
+ /*
|
|
+ * Since there's no opcode for futex_waitv, use
|
|
+ * FUTEX_WAIT_BITSET that uses absolute timeout as well
|
|
+ */
|
|
+ ret = futex_init_timeout(FUTEX_WAIT_BITSET, flag_init, &ts, &time);
|
|
+ if (ret)
|
|
+ return ret;
|
|
+
|
|
+ futex_setup_timer(&time, &to, flag_clkid, 0);
|
|
+ }
|
|
+
|
|
+ futexv = kcalloc(nr_futexes, sizeof(*futexv), GFP_KERNEL);
|
|
+ if (!futexv)
|
|
+ return -ENOMEM;
|
|
+
|
|
+ ret = futex_parse_waitv(futexv, waiters, nr_futexes);
|
|
+ if (!ret)
|
|
+ ret = futex_wait_multiple(futexv, nr_futexes, timeout ? &to : NULL);
|
|
+
|
|
+ if (timeout) {
|
|
+ hrtimer_cancel(&to.timer);
|
|
+ destroy_hrtimer_on_stack(&to.timer);
|
|
+ }
|
|
+
|
|
+ kfree(futexv);
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+#ifdef CONFIG_COMPAT
|
|
+COMPAT_SYSCALL_DEFINE2(set_robust_list,
|
|
+ struct compat_robust_list_head __user *, head,
|
|
+ compat_size_t, len)
|
|
+{
|
|
+ if (!futex_cmpxchg_enabled)
|
|
+ return -ENOSYS;
|
|
+
|
|
+ if (unlikely(len != sizeof(*head)))
|
|
+ return -EINVAL;
|
|
+
|
|
+ current->compat_robust_list = head;
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
|
|
+ compat_uptr_t __user *, head_ptr,
|
|
+ compat_size_t __user *, len_ptr)
|
|
+{
|
|
+ struct compat_robust_list_head __user *head;
|
|
+ unsigned long ret;
|
|
+ struct task_struct *p;
|
|
+
|
|
+ if (!futex_cmpxchg_enabled)
|
|
+ return -ENOSYS;
|
|
+
|
|
+ rcu_read_lock();
|
|
+
|
|
+ ret = -ESRCH;
|
|
+ if (!pid)
|
|
+ p = current;
|
|
+ else {
|
|
+ p = find_task_by_vpid(pid);
|
|
+ if (!p)
|
|
+ goto err_unlock;
|
|
+ }
|
|
+
|
|
+ ret = -EPERM;
|
|
+ if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
|
|
+ goto err_unlock;
|
|
+
|
|
+ head = p->compat_robust_list;
|
|
+ rcu_read_unlock();
|
|
+
|
|
+ if (put_user(sizeof(*head), len_ptr))
|
|
+ return -EFAULT;
|
|
+ return put_user(ptr_to_compat(head), head_ptr);
|
|
+
|
|
+err_unlock:
|
|
+ rcu_read_unlock();
|
|
+
|
|
+ return ret;
|
|
+}
|
|
+#endif /* CONFIG_COMPAT */
|
|
+
|
|
+#ifdef CONFIG_COMPAT_32BIT_TIME
|
|
+SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,
|
|
+ const struct old_timespec32 __user *, utime, u32 __user *, uaddr2,
|
|
+ u32, val3)
|
|
+{
|
|
+ int ret, cmd = op & FUTEX_CMD_MASK;
|
|
+ ktime_t t, *tp = NULL;
|
|
+ struct timespec64 ts;
|
|
+
|
|
+ if (utime && futex_cmd_has_timeout(cmd)) {
|
|
+ if (get_old_timespec32(&ts, utime))
|
|
+ return -EFAULT;
|
|
+ ret = futex_init_timeout(cmd, op, &ts, &t);
|
|
+ if (ret)
|
|
+ return ret;
|
|
+ tp = &t;
|
|
+ }
|
|
+
|
|
+ return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
|
|
+}
|
|
+#endif /* CONFIG_COMPAT_32BIT_TIME */
|
|
+
|
|
diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
|
|
new file mode 100644
|
|
index 000000000..b45597aab
|
|
--- /dev/null
|
|
+++ b/kernel/futex/waitwake.c
|
|
@@ -0,0 +1,708 @@
|
|
+// SPDX-License-Identifier: GPL-2.0-or-later
|
|
+
|
|
+#include <linux/sched/task.h>
|
|
+#include <linux/sched/signal.h>
|
|
+#include <linux/freezer.h>
|
|
+
|
|
+#include "futex.h"
|
|
+
|
|
+/*
|
|
+ * READ this before attempting to hack on futexes!
|
|
+ *
|
|
+ * Basic futex operation and ordering guarantees
|
|
+ * =============================================
|
|
+ *
|
|
+ * The waiter reads the futex value in user space and calls
|
|
+ * futex_wait(). This function computes the hash bucket and acquires
|
|
+ * the hash bucket lock. After that it reads the futex user space value
|
|
+ * again and verifies that the data has not changed. If it has not changed
|
|
+ * it enqueues itself into the hash bucket, releases the hash bucket lock
|
|
+ * and schedules.
|
|
+ *
|
|
+ * The waker side modifies the user space value of the futex and calls
|
|
+ * futex_wake(). This function computes the hash bucket and acquires the
|
|
+ * hash bucket lock. Then it looks for waiters on that futex in the hash
|
|
+ * bucket and wakes them.
|
|
+ *
|
|
+ * In futex wake up scenarios where no tasks are blocked on a futex, taking
|
|
+ * the hb spinlock can be avoided and simply return. In order for this
|
|
+ * optimization to work, ordering guarantees must exist so that the waiter
|
|
+ * being added to the list is acknowledged when the list is concurrently being
|
|
+ * checked by the waker, avoiding scenarios like the following:
|
|
+ *
|
|
+ * CPU 0 CPU 1
|
|
+ * val = *futex;
|
|
+ * sys_futex(WAIT, futex, val);
|
|
+ * futex_wait(futex, val);
|
|
+ * uval = *futex;
|
|
+ * *futex = newval;
|
|
+ * sys_futex(WAKE, futex);
|
|
+ * futex_wake(futex);
|
|
+ * if (queue_empty())
|
|
+ * return;
|
|
+ * if (uval == val)
|
|
+ * lock(hash_bucket(futex));
|
|
+ * queue();
|
|
+ * unlock(hash_bucket(futex));
|
|
+ * schedule();
|
|
+ *
|
|
+ * This would cause the waiter on CPU 0 to wait forever because it
|
|
+ * missed the transition of the user space value from val to newval
|
|
+ * and the waker did not find the waiter in the hash bucket queue.
|
|
+ *
|
|
+ * The correct serialization ensures that a waiter either observes
|
|
+ * the changed user space value before blocking or is woken by a
|
|
+ * concurrent waker:
|
|
+ *
|
|
+ * CPU 0 CPU 1
|
|
+ * val = *futex;
|
|
+ * sys_futex(WAIT, futex, val);
|
|
+ * futex_wait(futex, val);
|
|
+ *
|
|
+ * waiters++; (a)
|
|
+ * smp_mb(); (A) <-- paired with -.
|
|
+ * |
|
|
+ * lock(hash_bucket(futex)); |
|
|
+ * |
|
|
+ * uval = *futex; |
|
|
+ * | *futex = newval;
|
|
+ * | sys_futex(WAKE, futex);
|
|
+ * | futex_wake(futex);
|
|
+ * |
|
|
+ * `--------> smp_mb(); (B)
|
|
+ * if (uval == val)
|
|
+ * queue();
|
|
+ * unlock(hash_bucket(futex));
|
|
+ * schedule(); if (waiters)
|
|
+ * lock(hash_bucket(futex));
|
|
+ * else wake_waiters(futex);
|
|
+ * waiters--; (b) unlock(hash_bucket(futex));
|
|
+ *
|
|
+ * Where (A) orders the waiters increment and the futex value read through
|
|
+ * atomic operations (see futex_hb_waiters_inc) and where (B) orders the write
|
|
+ * to futex and the waiters read (see futex_hb_waiters_pending()).
|
|
+ *
|
|
+ * This yields the following case (where X:=waiters, Y:=futex):
|
|
+ *
|
|
+ * X = Y = 0
|
|
+ *
|
|
+ * w[X]=1 w[Y]=1
|
|
+ * MB MB
|
|
+ * r[Y]=y r[X]=x
|
|
+ *
|
|
+ * Which guarantees that x==0 && y==0 is impossible; which translates back into
|
|
+ * the guarantee that we cannot both miss the futex variable change and the
|
|
+ * enqueue.
|
|
+ *
|
|
+ * Note that a new waiter is accounted for in (a) even when it is possible that
|
|
+ * the wait call can return error, in which case we backtrack from it in (b).
|
|
+ * Refer to the comment in futex_q_lock().
|
|
+ *
|
|
+ * Similarly, in order to account for waiters being requeued on another
|
|
+ * address we always increment the waiters for the destination bucket before
|
|
+ * acquiring the lock. It then decrements them again after releasing it -
|
|
+ * the code that actually moves the futex(es) between hash buckets (requeue_futex)
|
|
+ * will do the additional required waiter count housekeeping. This is done for
|
|
+ * double_lock_hb() and double_unlock_hb(), respectively.
|
|
+ */
|
|
+
|
|
+/*
|
|
+ * The hash bucket lock must be held when this is called.
|
|
+ * Afterwards, the futex_q must not be accessed. Callers
|
|
+ * must ensure to later call wake_up_q() for the actual
|
|
+ * wakeups to occur.
|
|
+ */
|
|
+void futex_wake_mark(struct wake_q_head *wake_q, struct futex_q *q)
|
|
+{
|
|
+ struct task_struct *p = q->task;
|
|
+
|
|
+ if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n"))
|
|
+ return;
|
|
+
|
|
+ get_task_struct(p);
|
|
+ __futex_unqueue(q);
|
|
+ /*
|
|
+ * The waiting task can free the futex_q as soon as q->lock_ptr = NULL
|
|
+ * is written, without taking any locks. This is possible in the event
|
|
+ * of a spurious wakeup, for example. A memory barrier is required here
|
|
+ * to prevent the following store to lock_ptr from getting ahead of the
|
|
+ * plist_del in __futex_unqueue().
|
|
+ */
|
|
+ smp_store_release(&q->lock_ptr, NULL);
|
|
+
|
|
+ /*
|
|
+ * Queue the task for later wakeup for after we've released
|
|
+ * the hb->lock.
|
|
+ */
|
|
+ wake_q_add_safe(wake_q, p);
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Wake up waiters matching bitset queued on this futex (uaddr).
|
|
+ */
|
|
+int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
|
|
+{
|
|
+ struct futex_hash_bucket *hb;
|
|
+ struct futex_q *this, *next;
|
|
+ union futex_key key = FUTEX_KEY_INIT;
|
|
+ int ret;
|
|
+ DEFINE_WAKE_Q(wake_q);
|
|
+
|
|
+ if (!bitset)
|
|
+ return -EINVAL;
|
|
+
|
|
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, FUTEX_READ);
|
|
+ if (unlikely(ret != 0))
|
|
+ return ret;
|
|
+
|
|
+ hb = futex_hash(&key);
|
|
+
|
|
+ /* Make sure we really have tasks to wakeup */
|
|
+ if (!futex_hb_waiters_pending(hb))
|
|
+ return ret;
|
|
+
|
|
+ spin_lock(&hb->lock);
|
|
+
|
|
+ plist_for_each_entry_safe(this, next, &hb->chain, list) {
|
|
+ if (futex_match (&this->key, &key)) {
|
|
+ if (this->pi_state || this->rt_waiter) {
|
|
+ ret = -EINVAL;
|
|
+ break;
|
|
+ }
|
|
+
|
|
+ /* Check if one of the bits is set in both bitsets */
|
|
+ if (!(this->bitset & bitset))
|
|
+ continue;
|
|
+
|
|
+ futex_wake_mark(&wake_q, this);
|
|
+ if (++ret >= nr_wake)
|
|
+ break;
|
|
+ }
|
|
+ }
|
|
+
|
|
+ spin_unlock(&hb->lock);
|
|
+ wake_up_q(&wake_q);
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+static int futex_atomic_op_inuser(unsigned int encoded_op, u32 __user *uaddr)
|
|
+{
|
|
+ unsigned int op = (encoded_op & 0x70000000) >> 28;
|
|
+ unsigned int cmp = (encoded_op & 0x0f000000) >> 24;
|
|
+ int oparg = sign_extend32((encoded_op & 0x00fff000) >> 12, 11);
|
|
+ int cmparg = sign_extend32(encoded_op & 0x00000fff, 11);
|
|
+ int oldval, ret;
|
|
+
|
|
+ if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28)) {
|
|
+ if (oparg < 0 || oparg > 31) {
|
|
+ char comm[sizeof(current->comm)];
|
|
+ /*
|
|
+ * kill this print and return -EINVAL when userspace
|
|
+ * is sane again
|
|
+ */
|
|
+ pr_info_ratelimited("futex_wake_op: %s tries to shift op by %d; fix this program\n",
|
|
+ get_task_comm(comm, current), oparg);
|
|
+ oparg &= 31;
|
|
+ }
|
|
+ oparg = 1 << oparg;
|
|
+ }
|
|
+
|
|
+ pagefault_disable();
|
|
+ ret = arch_futex_atomic_op_inuser(op, oparg, &oldval, uaddr);
|
|
+ pagefault_enable();
|
|
+ if (ret)
|
|
+ return ret;
|
|
+
|
|
+ switch (cmp) {
|
|
+ case FUTEX_OP_CMP_EQ:
|
|
+ return oldval == cmparg;
|
|
+ case FUTEX_OP_CMP_NE:
|
|
+ return oldval != cmparg;
|
|
+ case FUTEX_OP_CMP_LT:
|
|
+ return oldval < cmparg;
|
|
+ case FUTEX_OP_CMP_GE:
|
|
+ return oldval >= cmparg;
|
|
+ case FUTEX_OP_CMP_LE:
|
|
+ return oldval <= cmparg;
|
|
+ case FUTEX_OP_CMP_GT:
|
|
+ return oldval > cmparg;
|
|
+ default:
|
|
+ return -ENOSYS;
|
|
+ }
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Wake up all waiters hashed on the physical page that is mapped
|
|
+ * to this virtual address:
|
|
+ */
|
|
+int futex_wake_op(u32 __user *uaddr1, unsigned int flags, u32 __user *uaddr2,
|
|
+ int nr_wake, int nr_wake2, int op)
|
|
+{
|
|
+ union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
|
|
+ struct futex_hash_bucket *hb1, *hb2;
|
|
+ struct futex_q *this, *next;
|
|
+ int ret, op_ret;
|
|
+ DEFINE_WAKE_Q(wake_q);
|
|
+
|
|
+retry:
|
|
+ ret = get_futex_key(uaddr1, flags & FLAGS_SHARED, &key1, FUTEX_READ);
|
|
+ if (unlikely(ret != 0))
|
|
+ return ret;
|
|
+ ret = get_futex_key(uaddr2, flags & FLAGS_SHARED, &key2, FUTEX_WRITE);
|
|
+ if (unlikely(ret != 0))
|
|
+ return ret;
|
|
+
|
|
+ hb1 = futex_hash(&key1);
|
|
+ hb2 = futex_hash(&key2);
|
|
+
|
|
+retry_private:
|
|
+ double_lock_hb(hb1, hb2);
|
|
+ op_ret = futex_atomic_op_inuser(op, uaddr2);
|
|
+ if (unlikely(op_ret < 0)) {
|
|
+ double_unlock_hb(hb1, hb2);
|
|
+
|
|
+ if (!IS_ENABLED(CONFIG_MMU) ||
|
|
+ unlikely(op_ret != -EFAULT && op_ret != -EAGAIN)) {
|
|
+ /*
|
|
+ * we don't get EFAULT from MMU faults if we don't have
|
|
+ * an MMU, but we might get them from range checking
|
|
+ */
|
|
+ ret = op_ret;
|
|
+ return ret;
|
|
+ }
|
|
+
|
|
+ if (op_ret == -EFAULT) {
|
|
+ ret = fault_in_user_writeable(uaddr2);
|
|
+ if (ret)
|
|
+ return ret;
|
|
+ }
|
|
+
|
|
+ cond_resched();
|
|
+ if (!(flags & FLAGS_SHARED))
|
|
+ goto retry_private;
|
|
+ goto retry;
|
|
+ }
|
|
+
|
|
+ plist_for_each_entry_safe(this, next, &hb1->chain, list) {
|
|
+ if (futex_match (&this->key, &key1)) {
|
|
+ if (this->pi_state || this->rt_waiter) {
|
|
+ ret = -EINVAL;
|
|
+ goto out_unlock;
|
|
+ }
|
|
+ futex_wake_mark(&wake_q, this);
|
|
+ if (++ret >= nr_wake)
|
|
+ break;
|
|
+ }
|
|
+ }
|
|
+
|
|
+ if (op_ret > 0) {
|
|
+ op_ret = 0;
|
|
+ plist_for_each_entry_safe(this, next, &hb2->chain, list) {
|
|
+ if (futex_match (&this->key, &key2)) {
|
|
+ if (this->pi_state || this->rt_waiter) {
|
|
+ ret = -EINVAL;
|
|
+ goto out_unlock;
|
|
+ }
|
|
+ futex_wake_mark(&wake_q, this);
|
|
+ if (++op_ret >= nr_wake2)
|
|
+ break;
|
|
+ }
|
|
+ }
|
|
+ ret += op_ret;
|
|
+ }
|
|
+
|
|
+out_unlock:
|
|
+ double_unlock_hb(hb1, hb2);
|
|
+ wake_up_q(&wake_q);
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+static long futex_wait_restart(struct restart_block *restart);
|
|
+
|
|
+/**
|
|
+ * futex_wait_queue() - futex_queue() and wait for wakeup, timeout, or signal
|
|
+ * @hb: the futex hash bucket, must be locked by the caller
|
|
+ * @q: the futex_q to queue up on
|
|
+ * @timeout: the prepared hrtimer_sleeper, or null for no timeout
|
|
+ */
|
|
+void futex_wait_queue(struct futex_hash_bucket *hb, struct futex_q *q,
|
|
+ struct hrtimer_sleeper *timeout)
|
|
+{
|
|
+ /*
|
|
+ * The task state is guaranteed to be set before another task can
|
|
+ * wake it. set_current_state() is implemented using smp_store_mb() and
|
|
+ * futex_queue() calls spin_unlock() upon completion, both serializing
|
|
+ * access to the hash list and forcing another memory barrier.
|
|
+ */
|
|
+ set_current_state(TASK_INTERRUPTIBLE);
|
|
+ futex_queue(q, hb);
|
|
+
|
|
+ /* Arm the timer */
|
|
+ if (timeout)
|
|
+ hrtimer_sleeper_start_expires(timeout, HRTIMER_MODE_ABS);
|
|
+
|
|
+ /*
|
|
+ * If we have been removed from the hash list, then another task
|
|
+ * has tried to wake us, and we can skip the call to schedule().
|
|
+ */
|
|
+ if (likely(!plist_node_empty(&q->list))) {
|
|
+ /*
|
|
+ * If the timer has already expired, current will already be
|
|
+ * flagged for rescheduling. Only call schedule if there
|
|
+ * is no timeout, or if it has yet to expire.
|
|
+ */
|
|
+ if (!timeout || timeout->task)
|
|
+ freezable_schedule();
|
|
+ }
|
|
+ __set_current_state(TASK_RUNNING);
|
|
+}
|
|
+
|
|
+/**
|
|
+ * unqueue_multiple - Remove various futexes from their hash bucket
|
|
+ * @v: The list of futexes to unqueue
|
|
+ * @count: Number of futexes in the list
|
|
+ *
|
|
+ * Helper to unqueue a list of futexes. This can't fail.
|
|
+ *
|
|
+ * Return:
|
|
+ * - >=0 - Index of the last futex that was awoken;
|
|
+ * - -1 - No futex was awoken
|
|
+ */
|
|
+static int unqueue_multiple(struct futex_vector *v, int count)
|
|
+{
|
|
+ int ret = -1, i;
|
|
+
|
|
+ for (i = 0; i < count; i++) {
|
|
+ if (!futex_unqueue(&v[i].q))
|
|
+ ret = i;
|
|
+ }
|
|
+
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_wait_multiple_setup - Prepare to wait and enqueue multiple futexes
|
|
+ * @vs: The futex list to wait on
|
|
+ * @count: The size of the list
|
|
+ * @awaken: Index of the last awoken futex, if any. Used to notify the
|
|
+ * caller that it can return this index to userspace (return parameter)
|
|
+ *
|
|
+ * Prepare multiple futexes in a single step and enqueue them. This may fail if
|
|
+ * the futex list is invalid or if any futex was already awoken. On success the
|
|
+ * task is ready to interruptible sleep.
|
|
+ *
|
|
+ * Return:
|
|
+ * - 1 - One of the futexes was awaken by another thread
|
|
+ * - 0 - Success
|
|
+ * - <0 - -EFAULT, -EWOULDBLOCK or -EINVAL
|
|
+ */
|
|
+static int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *awaken)
|
|
+{
|
|
+ struct futex_hash_bucket *hb;
|
|
+ bool retry = false;
|
|
+ int ret, i;
|
|
+ u32 uval;
|
|
+
|
|
+ /*
|
|
+ * Enqueuing multiple futexes is tricky, because we need to enqueue
|
|
+ * each futex in the list before dealing with the next one to avoid
|
|
+ * deadlocking on the hash bucket. But, before enqueuing, we need to
|
|
+ * make sure that current->state is TASK_INTERRUPTIBLE, so we don't
|
|
+ * absorb any awake events, which cannot be done before the
|
|
+ * get_futex_key of the next key, because it calls get_user_pages,
|
|
+ * which can sleep. Thus, we fetch the list of futexes keys in two
|
|
+ * steps, by first pinning all the memory keys in the futex key, and
|
|
+ * only then we read each key and queue the corresponding futex.
|
|
+ *
|
|
+ * Private futexes doesn't need to recalculate hash in retry, so skip
|
|
+ * get_futex_key() when retrying.
|
|
+ */
|
|
+retry:
|
|
+ for (i = 0; i < count; i++) {
|
|
+ if ((vs[i].w.flags & FUTEX_PRIVATE_FLAG) && retry)
|
|
+ continue;
|
|
+
|
|
+ ret = get_futex_key(u64_to_user_ptr(vs[i].w.uaddr),
|
|
+ !(vs[i].w.flags & FUTEX_PRIVATE_FLAG),
|
|
+ &vs[i].q.key, FUTEX_READ);
|
|
+
|
|
+ if (unlikely(ret))
|
|
+ return ret;
|
|
+ }
|
|
+
|
|
+ set_current_state(TASK_INTERRUPTIBLE);
|
|
+
|
|
+ for (i = 0; i < count; i++) {
|
|
+ u32 __user *uaddr = (u32 __user *)(unsigned long)vs[i].w.uaddr;
|
|
+ struct futex_q *q = &vs[i].q;
|
|
+ u32 val = (u32)vs[i].w.val;
|
|
+
|
|
+ hb = futex_q_lock(q);
|
|
+ ret = futex_get_value_locked(&uval, uaddr);
|
|
+
|
|
+ if (!ret && uval == val) {
|
|
+ /*
|
|
+ * The bucket lock can't be held while dealing with the
|
|
+ * next futex. Queue each futex at this moment so hb can
|
|
+ * be unlocked.
|
|
+ */
|
|
+ futex_queue(q, hb);
|
|
+ continue;
|
|
+ }
|
|
+
|
|
+ futex_q_unlock(hb);
|
|
+ __set_current_state(TASK_RUNNING);
|
|
+
|
|
+ /*
|
|
+ * Even if something went wrong, if we find out that a futex
|
|
+ * was awaken, we don't return error and return this index to
|
|
+ * userspace
|
|
+ */
|
|
+ *awaken = unqueue_multiple(vs, i);
|
|
+ if (*awaken >= 0)
|
|
+ return 1;
|
|
+
|
|
+ if (ret) {
|
|
+ /*
|
|
+ * If we need to handle a page fault, we need to do so
|
|
+ * without any lock and any enqueued futex (otherwise
|
|
+ * we could lose some wakeup). So we do it here, after
|
|
+ * undoing all the work done so far. In success, we
|
|
+ * retry all the work.
|
|
+ */
|
|
+ if (get_user(uval, uaddr))
|
|
+ return -EFAULT;
|
|
+
|
|
+ retry = true;
|
|
+ goto retry;
|
|
+ }
|
|
+
|
|
+ if (uval != val)
|
|
+ return -EWOULDBLOCK;
|
|
+ }
|
|
+
|
|
+ return 0;
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_sleep_multiple - Check sleeping conditions and sleep
|
|
+ * @vs: List of futexes to wait for
|
|
+ * @count: Length of vs
|
|
+ * @to: Timeout
|
|
+ *
|
|
+ * Sleep if and only if the timeout hasn't expired and no futex on the list has
|
|
+ * been awaken.
|
|
+ */
|
|
+static void futex_sleep_multiple(struct futex_vector *vs, unsigned int count,
|
|
+ struct hrtimer_sleeper *to)
|
|
+{
|
|
+ if (to && !to->task)
|
|
+ return;
|
|
+
|
|
+ for (; count; count--, vs++) {
|
|
+ if (!READ_ONCE(vs->q.lock_ptr))
|
|
+ return;
|
|
+ }
|
|
+
|
|
+ freezable_schedule();
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_wait_multiple - Prepare to wait on and enqueue several futexes
|
|
+ * @vs: The list of futexes to wait on
|
|
+ * @count: The number of objects
|
|
+ * @to: Timeout before giving up and returning to userspace
|
|
+ *
|
|
+ * Entry point for the FUTEX_WAIT_MULTIPLE futex operation, this function
|
|
+ * sleeps on a group of futexes and returns on the first futex that is
|
|
+ * wake, or after the timeout has elapsed.
|
|
+ *
|
|
+ * Return:
|
|
+ * - >=0 - Hint to the futex that was awoken
|
|
+ * - <0 - On error
|
|
+ */
|
|
+int futex_wait_multiple(struct futex_vector *vs, unsigned int count,
|
|
+ struct hrtimer_sleeper *to)
|
|
+{
|
|
+ int ret, hint = 0;
|
|
+
|
|
+ if (to)
|
|
+ hrtimer_sleeper_start_expires(to, HRTIMER_MODE_ABS);
|
|
+
|
|
+ while (1) {
|
|
+ ret = futex_wait_multiple_setup(vs, count, &hint);
|
|
+ if (ret) {
|
|
+ if (ret > 0) {
|
|
+ /* A futex was awaken during setup */
|
|
+ ret = hint;
|
|
+ }
|
|
+ return ret;
|
|
+ }
|
|
+
|
|
+ futex_sleep_multiple(vs, count, to);
|
|
+
|
|
+ __set_current_state(TASK_RUNNING);
|
|
+
|
|
+ ret = unqueue_multiple(vs, count);
|
|
+ if (ret >= 0)
|
|
+ return ret;
|
|
+
|
|
+ if (to && !to->task)
|
|
+ return -ETIMEDOUT;
|
|
+ else if (signal_pending(current))
|
|
+ return -ERESTARTSYS;
|
|
+ /*
|
|
+ * The final case is a spurious wakeup, for
|
|
+ * which just retry.
|
|
+ */
|
|
+ }
|
|
+}
|
|
+
|
|
+/**
|
|
+ * futex_wait_setup() - Prepare to wait on a futex
|
|
+ * @uaddr: the futex userspace address
|
|
+ * @val: the expected value
|
|
+ * @flags: futex flags (FLAGS_SHARED, etc.)
|
|
+ * @q: the associated futex_q
|
|
+ * @hb: storage for hash_bucket pointer to be returned to caller
|
|
+ *
|
|
+ * Setup the futex_q and locate the hash_bucket. Get the futex value and
|
|
+ * compare it with the expected value. Handle atomic faults internally.
|
|
+ * Return with the hb lock held on success, and unlocked on failure.
|
|
+ *
|
|
+ * Return:
|
|
+ * - 0 - uaddr contains val and hb has been locked;
|
|
+ * - <1 - -EFAULT or -EWOULDBLOCK (uaddr does not contain val) and hb is unlocked
|
|
+ */
|
|
+int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags,
|
|
+ struct futex_q *q, struct futex_hash_bucket **hb)
|
|
+{
|
|
+ u32 uval;
|
|
+ int ret;
|
|
+
|
|
+ /*
|
|
+ * Access the page AFTER the hash-bucket is locked.
|
|
+ * Order is important:
|
|
+ *
|
|
+ * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
|
|
+ * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
|
|
+ *
|
|
+ * The basic logical guarantee of a futex is that it blocks ONLY
|
|
+ * if cond(var) is known to be true at the time of blocking, for
|
|
+ * any cond. If we locked the hash-bucket after testing *uaddr, that
|
|
+ * would open a race condition where we could block indefinitely with
|
|
+ * cond(var) false, which would violate the guarantee.
|
|
+ *
|
|
+ * On the other hand, we insert q and release the hash-bucket only
|
|
+ * after testing *uaddr. This guarantees that futex_wait() will NOT
|
|
+ * absorb a wakeup if *uaddr does not match the desired values
|
|
+ * while the syscall executes.
|
|
+ */
|
|
+retry:
|
|
+ ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q->key, FUTEX_READ);
|
|
+ if (unlikely(ret != 0))
|
|
+ return ret;
|
|
+
|
|
+retry_private:
|
|
+ *hb = futex_q_lock(q);
|
|
+
|
|
+ ret = futex_get_value_locked(&uval, uaddr);
|
|
+
|
|
+ if (ret) {
|
|
+ futex_q_unlock(*hb);
|
|
+
|
|
+ ret = get_user(uval, uaddr);
|
|
+ if (ret)
|
|
+ return ret;
|
|
+
|
|
+ if (!(flags & FLAGS_SHARED))
|
|
+ goto retry_private;
|
|
+
|
|
+ goto retry;
|
|
+ }
|
|
+
|
|
+ if (uval != val) {
|
|
+ futex_q_unlock(*hb);
|
|
+ ret = -EWOULDBLOCK;
|
|
+ }
|
|
+
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+int futex_wait(u32 __user *uaddr, unsigned int flags, u32 val, ktime_t *abs_time, u32 bitset)
|
|
+{
|
|
+ struct hrtimer_sleeper timeout, *to;
|
|
+ struct restart_block *restart;
|
|
+ struct futex_hash_bucket *hb;
|
|
+ struct futex_q q = futex_q_init;
|
|
+ int ret;
|
|
+
|
|
+ if (!bitset)
|
|
+ return -EINVAL;
|
|
+ q.bitset = bitset;
|
|
+
|
|
+ to = futex_setup_timer(abs_time, &timeout, flags,
|
|
+ current->timer_slack_ns);
|
|
+retry:
|
|
+ /*
|
|
+ * Prepare to wait on uaddr. On success, it holds hb->lock and q
|
|
+ * is initialized.
|
|
+ */
|
|
+ ret = futex_wait_setup(uaddr, val, flags, &q, &hb);
|
|
+ if (ret)
|
|
+ goto out;
|
|
+
|
|
+ /* futex_queue and wait for wakeup, timeout, or a signal. */
|
|
+ futex_wait_queue(hb, &q, to);
|
|
+
|
|
+ /* If we were woken (and unqueued), we succeeded, whatever. */
|
|
+ ret = 0;
|
|
+ if (!futex_unqueue(&q))
|
|
+ goto out;
|
|
+ ret = -ETIMEDOUT;
|
|
+ if (to && !to->task)
|
|
+ goto out;
|
|
+
|
|
+ /*
|
|
+ * We expect signal_pending(current), but we might be the
|
|
+ * victim of a spurious wakeup as well.
|
|
+ */
|
|
+ if (!signal_pending(current))
|
|
+ goto retry;
|
|
+
|
|
+ ret = -ERESTARTSYS;
|
|
+ if (!abs_time)
|
|
+ goto out;
|
|
+
|
|
+ restart = ¤t->restart_block;
|
|
+ restart->futex.uaddr = uaddr;
|
|
+ restart->futex.val = val;
|
|
+ restart->futex.time = *abs_time;
|
|
+ restart->futex.bitset = bitset;
|
|
+ restart->futex.flags = flags | FLAGS_HAS_TIMEOUT;
|
|
+
|
|
+ ret = set_restart_fn(restart, futex_wait_restart);
|
|
+
|
|
+out:
|
|
+ if (to) {
|
|
+ hrtimer_cancel(&to->timer);
|
|
+ destroy_hrtimer_on_stack(&to->timer);
|
|
+ }
|
|
+ return ret;
|
|
+}
|
|
+
|
|
+static long futex_wait_restart(struct restart_block *restart)
|
|
+{
|
|
+ u32 __user *uaddr = restart->futex.uaddr;
|
|
+ ktime_t t, *tp = NULL;
|
|
+
|
|
+ if (restart->futex.flags & FLAGS_HAS_TIMEOUT) {
|
|
+ t = restart->futex.time;
|
|
+ tp = &t;
|
|
+ }
|
|
+ restart->fn = do_no_restart_syscall;
|
|
+
|
|
+ return (long)futex_wait(uaddr, restart->futex.flags,
|
|
+ restart->futex.val, tp, restart->futex.bitset);
|
|
+}
|
|
+
|
|
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
|
|
index f43d89d92..d1944258c 100644
|
|
--- a/kernel/sys_ni.c
|
|
+++ b/kernel/sys_ni.c
|
|
@@ -143,13 +143,14 @@ COND_SYSCALL(capset);
|
|
/* __ARCH_WANT_SYS_CLONE3 */
|
|
COND_SYSCALL(clone3);
|
|
|
|
-/* kernel/futex.c */
|
|
+/* kernel/futex/syscalls.c */
|
|
COND_SYSCALL(futex);
|
|
COND_SYSCALL(futex_time32);
|
|
COND_SYSCALL(set_robust_list);
|
|
COND_SYSCALL_COMPAT(set_robust_list);
|
|
COND_SYSCALL(get_robust_list);
|
|
COND_SYSCALL_COMPAT(get_robust_list);
|
|
+COND_SYSCALL(futex_waitv);
|
|
|
|
/* kernel/hrtimer.c */
|
|
|
|
diff --git a/tools/testing/selftests/futex/functional/.gitignore b/tools/testing/selftests/futex/functional/.gitignore
|
|
index 0e78b49d0..fbcbdb696 100644
|
|
--- a/tools/testing/selftests/futex/functional/.gitignore
|
|
+++ b/tools/testing/selftests/futex/functional/.gitignore
|
|
@@ -8,3 +8,4 @@ futex_wait_uninitialized_heap
|
|
futex_wait_wouldblock
|
|
futex_wait
|
|
futex_requeue
|
|
+futex_waitv
|
|
diff --git a/tools/testing/selftests/futex/functional/Makefile b/tools/testing/selftests/futex/functional/Makefile
|
|
index bd1fec59e..5cc38de9d 100644
|
|
--- a/tools/testing/selftests/futex/functional/Makefile
|
|
+++ b/tools/testing/selftests/futex/functional/Makefile
|
|
@@ -17,7 +17,8 @@ TEST_GEN_FILES := \
|
|
futex_wait_uninitialized_heap \
|
|
futex_wait_private_mapped_file \
|
|
futex_wait \
|
|
- futex_requeue
|
|
+ futex_requeue \
|
|
+ futex_waitv
|
|
|
|
TEST_PROGS := run.sh
|
|
|
|
diff --git a/tools/testing/selftests/futex/functional/futex_wait_timeout.c b/tools/testing/selftests/futex/functional/futex_wait_timeout.c
|
|
index 1f8f6daaf..3651ce17b 100644
|
|
--- a/tools/testing/selftests/futex/functional/futex_wait_timeout.c
|
|
+++ b/tools/testing/selftests/futex/functional/futex_wait_timeout.c
|
|
@@ -17,6 +17,7 @@
|
|
|
|
#include <pthread.h>
|
|
#include "futextest.h"
|
|
+#include "futex2test.h"
|
|
#include "logging.h"
|
|
|
|
#define TEST_NAME "futex-wait-timeout"
|
|
@@ -96,6 +97,12 @@ int main(int argc, char *argv[])
|
|
struct timespec to;
|
|
pthread_t thread;
|
|
int c;
|
|
+ struct futex_waitv waitv = {
|
|
+ .uaddr = (uintptr_t)&f1,
|
|
+ .val = f1,
|
|
+ .flags = FUTEX_32,
|
|
+ .__reserved = 0
|
|
+ };
|
|
|
|
while ((c = getopt(argc, argv, "cht:v:")) != -1) {
|
|
switch (c) {
|
|
@@ -118,7 +125,7 @@ int main(int argc, char *argv[])
|
|
}
|
|
|
|
ksft_print_header();
|
|
- ksft_set_plan(7);
|
|
+ ksft_set_plan(9);
|
|
ksft_print_msg("%s: Block on a futex and wait for timeout\n",
|
|
basename(argv[0]));
|
|
ksft_print_msg("\tArguments: timeout=%ldns\n", timeout_ns);
|
|
@@ -175,6 +182,18 @@ int main(int argc, char *argv[])
|
|
res = futex_lock_pi(&futex_pi, NULL, 0, FUTEX_CLOCK_REALTIME);
|
|
test_timeout(res, &ret, "futex_lock_pi invalid timeout flag", ENOSYS);
|
|
|
|
+ /* futex_waitv with CLOCK_MONOTONIC */
|
|
+ if (futex_get_abs_timeout(CLOCK_MONOTONIC, &to, timeout_ns))
|
|
+ return RET_FAIL;
|
|
+ res = futex_waitv(&waitv, 1, 0, &to, CLOCK_MONOTONIC);
|
|
+ test_timeout(res, &ret, "futex_waitv monotonic", ETIMEDOUT);
|
|
+
|
|
+ /* futex_waitv with CLOCK_REALTIME */
|
|
+ if (futex_get_abs_timeout(CLOCK_REALTIME, &to, timeout_ns))
|
|
+ return RET_FAIL;
|
|
+ res = futex_waitv(&waitv, 1, 0, &to, CLOCK_REALTIME);
|
|
+ test_timeout(res, &ret, "futex_waitv realtime", ETIMEDOUT);
|
|
+
|
|
ksft_print_cnts();
|
|
return ret;
|
|
}
|
|
diff --git a/tools/testing/selftests/futex/functional/futex_wait_wouldblock.c b/tools/testing/selftests/futex/functional/futex_wait_wouldblock.c
|
|
index 0ae390ff8..7d7a6a06c 100644
|
|
--- a/tools/testing/selftests/futex/functional/futex_wait_wouldblock.c
|
|
+++ b/tools/testing/selftests/futex/functional/futex_wait_wouldblock.c
|
|
@@ -22,6 +22,7 @@
|
|
#include <string.h>
|
|
#include <time.h>
|
|
#include "futextest.h"
|
|
+#include "futex2test.h"
|
|
#include "logging.h"
|
|
|
|
#define TEST_NAME "futex-wait-wouldblock"
|
|
@@ -42,6 +43,12 @@ int main(int argc, char *argv[])
|
|
futex_t f1 = FUTEX_INITIALIZER;
|
|
int res, ret = RET_PASS;
|
|
int c;
|
|
+ struct futex_waitv waitv = {
|
|
+ .uaddr = (uintptr_t)&f1,
|
|
+ .val = f1+1,
|
|
+ .flags = FUTEX_32,
|
|
+ .__reserved = 0
|
|
+ };
|
|
|
|
while ((c = getopt(argc, argv, "cht:v:")) != -1) {
|
|
switch (c) {
|
|
@@ -61,18 +68,44 @@ int main(int argc, char *argv[])
|
|
}
|
|
|
|
ksft_print_header();
|
|
- ksft_set_plan(1);
|
|
+ ksft_set_plan(2);
|
|
ksft_print_msg("%s: Test the unexpected futex value in FUTEX_WAIT\n",
|
|
basename(argv[0]));
|
|
|
|
info("Calling futex_wait on f1: %u @ %p with val=%u\n", f1, &f1, f1+1);
|
|
res = futex_wait(&f1, f1+1, &to, FUTEX_PRIVATE_FLAG);
|
|
if (!res || errno != EWOULDBLOCK) {
|
|
- fail("futex_wait returned: %d %s\n",
|
|
- res ? errno : res, res ? strerror(errno) : "");
|
|
+ ksft_test_result_fail("futex_wait returned: %d %s\n",
|
|
+ res ? errno : res,
|
|
+ res ? strerror(errno) : "");
|
|
ret = RET_FAIL;
|
|
+ } else {
|
|
+ ksft_test_result_pass("futex_wait\n");
|
|
}
|
|
|
|
- print_result(TEST_NAME, ret);
|
|
+ if (clock_gettime(CLOCK_MONOTONIC, &to)) {
|
|
+ error("clock_gettime failed\n", errno);
|
|
+ return errno;
|
|
+ }
|
|
+
|
|
+ to.tv_nsec += timeout_ns;
|
|
+
|
|
+ if (to.tv_nsec >= 1000000000) {
|
|
+ to.tv_sec++;
|
|
+ to.tv_nsec -= 1000000000;
|
|
+ }
|
|
+
|
|
+ info("Calling futex_waitv on f1: %u @ %p with val=%u\n", f1, &f1, f1+1);
|
|
+ res = futex_waitv(&waitv, 1, 0, &to, CLOCK_MONOTONIC);
|
|
+ if (!res || errno != EWOULDBLOCK) {
|
|
+ ksft_test_result_pass("futex_waitv returned: %d %s\n",
|
|
+ res ? errno : res,
|
|
+ res ? strerror(errno) : "");
|
|
+ ret = RET_FAIL;
|
|
+ } else {
|
|
+ ksft_test_result_pass("futex_waitv\n");
|
|
+ }
|
|
+
|
|
+ ksft_print_cnts();
|
|
return ret;
|
|
}
|
|
diff --git a/tools/testing/selftests/futex/functional/futex_waitv.c b/tools/testing/selftests/futex/functional/futex_waitv.c
|
|
new file mode 100644
|
|
index 000000000..a94337f67
|
|
--- /dev/null
|
|
+++ b/tools/testing/selftests/futex/functional/futex_waitv.c
|
|
@@ -0,0 +1,237 @@
|
|
+// SPDX-License-Identifier: GPL-2.0-or-later
|
|
+/*
|
|
+ * futex_waitv() test by André Almeida <andrealmeid@collabora.com>
|
|
+ *
|
|
+ * Copyright 2021 Collabora Ltd.
|
|
+ */
|
|
+
|
|
+#include <errno.h>
|
|
+#include <error.h>
|
|
+#include <getopt.h>
|
|
+#include <stdio.h>
|
|
+#include <stdlib.h>
|
|
+#include <string.h>
|
|
+#include <time.h>
|
|
+#include <pthread.h>
|
|
+#include <stdint.h>
|
|
+#include <sys/shm.h>
|
|
+#include "futextest.h"
|
|
+#include "futex2test.h"
|
|
+#include "logging.h"
|
|
+
|
|
+#define TEST_NAME "futex-wait"
|
|
+#define WAKE_WAIT_US 10000
|
|
+#define NR_FUTEXES 30
|
|
+static struct futex_waitv waitv[NR_FUTEXES];
|
|
+u_int32_t futexes[NR_FUTEXES] = {0};
|
|
+
|
|
+void usage(char *prog)
|
|
+{
|
|
+ printf("Usage: %s\n", prog);
|
|
+ printf(" -c Use color\n");
|
|
+ printf(" -h Display this help message\n");
|
|
+ printf(" -v L Verbosity level: %d=QUIET %d=CRITICAL %d=INFO\n",
|
|
+ VQUIET, VCRITICAL, VINFO);
|
|
+}
|
|
+
|
|
+void *waiterfn(void *arg)
|
|
+{
|
|
+ struct timespec to;
|
|
+ int res;
|
|
+
|
|
+ /* setting absolute timeout for futex2 */
|
|
+ if (clock_gettime(CLOCK_MONOTONIC, &to))
|
|
+ error("gettime64 failed\n", errno);
|
|
+
|
|
+ to.tv_sec++;
|
|
+
|
|
+ res = futex_waitv(waitv, NR_FUTEXES, 0, &to, CLOCK_MONOTONIC);
|
|
+ if (res < 0) {
|
|
+ ksft_test_result_fail("futex_waitv returned: %d %s\n",
|
|
+ errno, strerror(errno));
|
|
+ } else if (res != NR_FUTEXES - 1) {
|
|
+ ksft_test_result_fail("futex_waitv returned: %d, expecting %d\n",
|
|
+ res, NR_FUTEXES - 1);
|
|
+ }
|
|
+
|
|
+ return NULL;
|
|
+}
|
|
+
|
|
+int main(int argc, char *argv[])
|
|
+{
|
|
+ pthread_t waiter;
|
|
+ int res, ret = RET_PASS;
|
|
+ struct timespec to;
|
|
+ int c, i;
|
|
+
|
|
+ while ((c = getopt(argc, argv, "cht:v:")) != -1) {
|
|
+ switch (c) {
|
|
+ case 'c':
|
|
+ log_color(1);
|
|
+ break;
|
|
+ case 'h':
|
|
+ usage(basename(argv[0]));
|
|
+ exit(0);
|
|
+ case 'v':
|
|
+ log_verbosity(atoi(optarg));
|
|
+ break;
|
|
+ default:
|
|
+ usage(basename(argv[0]));
|
|
+ exit(1);
|
|
+ }
|
|
+ }
|
|
+
|
|
+ ksft_print_header();
|
|
+ ksft_set_plan(7);
|
|
+ ksft_print_msg("%s: Test FUTEX_WAITV\n",
|
|
+ basename(argv[0]));
|
|
+
|
|
+ for (i = 0; i < NR_FUTEXES; i++) {
|
|
+ waitv[i].uaddr = (uintptr_t)&futexes[i];
|
|
+ waitv[i].flags = FUTEX_32 | FUTEX_PRIVATE_FLAG;
|
|
+ waitv[i].val = 0;
|
|
+ waitv[i].__reserved = 0;
|
|
+ }
|
|
+
|
|
+ /* Private waitv */
|
|
+ if (pthread_create(&waiter, NULL, waiterfn, NULL))
|
|
+ error("pthread_create failed\n", errno);
|
|
+
|
|
+ usleep(WAKE_WAIT_US);
|
|
+
|
|
+ res = futex_wake(u64_to_ptr(waitv[NR_FUTEXES - 1].uaddr), 1, FUTEX_PRIVATE_FLAG);
|
|
+ if (res != 1) {
|
|
+ ksft_test_result_fail("futex_wake private returned: %d %s\n",
|
|
+ res ? errno : res,
|
|
+ res ? strerror(errno) : "");
|
|
+ ret = RET_FAIL;
|
|
+ } else {
|
|
+ ksft_test_result_pass("futex_waitv private\n");
|
|
+ }
|
|
+
|
|
+ /* Shared waitv */
|
|
+ for (i = 0; i < NR_FUTEXES; i++) {
|
|
+ int shm_id = shmget(IPC_PRIVATE, 4096, IPC_CREAT | 0666);
|
|
+
|
|
+ if (shm_id < 0) {
|
|
+ perror("shmget");
|
|
+ exit(1);
|
|
+ }
|
|
+
|
|
+ unsigned int *shared_data = shmat(shm_id, NULL, 0);
|
|
+
|
|
+ *shared_data = 0;
|
|
+ waitv[i].uaddr = (uintptr_t)shared_data;
|
|
+ waitv[i].flags = FUTEX_32;
|
|
+ waitv[i].val = 0;
|
|
+ waitv[i].__reserved = 0;
|
|
+ }
|
|
+
|
|
+ if (pthread_create(&waiter, NULL, waiterfn, NULL))
|
|
+ error("pthread_create failed\n", errno);
|
|
+
|
|
+ usleep(WAKE_WAIT_US);
|
|
+
|
|
+ res = futex_wake(u64_to_ptr(waitv[NR_FUTEXES - 1].uaddr), 1, 0);
|
|
+ if (res != 1) {
|
|
+ ksft_test_result_fail("futex_wake shared returned: %d %s\n",
|
|
+ res ? errno : res,
|
|
+ res ? strerror(errno) : "");
|
|
+ ret = RET_FAIL;
|
|
+ } else {
|
|
+ ksft_test_result_pass("futex_waitv shared\n");
|
|
+ }
|
|
+
|
|
+ for (i = 0; i < NR_FUTEXES; i++)
|
|
+ shmdt(u64_to_ptr(waitv[i].uaddr));
|
|
+
|
|
+ /* Testing a waiter without FUTEX_32 flag */
|
|
+ waitv[0].flags = FUTEX_PRIVATE_FLAG;
|
|
+
|
|
+ if (clock_gettime(CLOCK_MONOTONIC, &to))
|
|
+ error("gettime64 failed\n", errno);
|
|
+
|
|
+ to.tv_sec++;
|
|
+
|
|
+ res = futex_waitv(waitv, NR_FUTEXES, 0, &to, CLOCK_MONOTONIC);
|
|
+ if (res == EINVAL) {
|
|
+ ksft_test_result_fail("futex_waitv private returned: %d %s\n",
|
|
+ res ? errno : res,
|
|
+ res ? strerror(errno) : "");
|
|
+ ret = RET_FAIL;
|
|
+ } else {
|
|
+ ksft_test_result_pass("futex_waitv without FUTEX_32\n");
|
|
+ }
|
|
+
|
|
+ /* Testing a waiter with an unaligned address */
|
|
+ waitv[0].flags = FUTEX_PRIVATE_FLAG | FUTEX_32;
|
|
+ waitv[0].uaddr = 1;
|
|
+
|
|
+ if (clock_gettime(CLOCK_MONOTONIC, &to))
|
|
+ error("gettime64 failed\n", errno);
|
|
+
|
|
+ to.tv_sec++;
|
|
+
|
|
+ res = futex_waitv(waitv, NR_FUTEXES, 0, &to, CLOCK_MONOTONIC);
|
|
+ if (res == EINVAL) {
|
|
+ ksft_test_result_fail("futex_wake private returned: %d %s\n",
|
|
+ res ? errno : res,
|
|
+ res ? strerror(errno) : "");
|
|
+ ret = RET_FAIL;
|
|
+ } else {
|
|
+ ksft_test_result_pass("futex_waitv with an unaligned address\n");
|
|
+ }
|
|
+
|
|
+ /* Testing a NULL address for waiters.uaddr */
|
|
+ waitv[0].uaddr = 0x00000000;
|
|
+
|
|
+ if (clock_gettime(CLOCK_MONOTONIC, &to))
|
|
+ error("gettime64 failed\n", errno);
|
|
+
|
|
+ to.tv_sec++;
|
|
+
|
|
+ res = futex_waitv(waitv, NR_FUTEXES, 0, &to, CLOCK_MONOTONIC);
|
|
+ if (res == EINVAL) {
|
|
+ ksft_test_result_fail("futex_waitv private returned: %d %s\n",
|
|
+ res ? errno : res,
|
|
+ res ? strerror(errno) : "");
|
|
+ ret = RET_FAIL;
|
|
+ } else {
|
|
+ ksft_test_result_pass("futex_waitv NULL address in waitv.uaddr\n");
|
|
+ }
|
|
+
|
|
+ /* Testing a NULL address for *waiters */
|
|
+ if (clock_gettime(CLOCK_MONOTONIC, &to))
|
|
+ error("gettime64 failed\n", errno);
|
|
+
|
|
+ to.tv_sec++;
|
|
+
|
|
+ res = futex_waitv(NULL, NR_FUTEXES, 0, &to, CLOCK_MONOTONIC);
|
|
+ if (res == EINVAL) {
|
|
+ ksft_test_result_fail("futex_waitv private returned: %d %s\n",
|
|
+ res ? errno : res,
|
|
+ res ? strerror(errno) : "");
|
|
+ ret = RET_FAIL;
|
|
+ } else {
|
|
+ ksft_test_result_pass("futex_waitv NULL address in *waiters\n");
|
|
+ }
|
|
+
|
|
+ /* Testing an invalid clockid */
|
|
+ if (clock_gettime(CLOCK_MONOTONIC, &to))
|
|
+ error("gettime64 failed\n", errno);
|
|
+
|
|
+ to.tv_sec++;
|
|
+
|
|
+ res = futex_waitv(NULL, NR_FUTEXES, 0, &to, CLOCK_TAI);
|
|
+ if (res == EINVAL) {
|
|
+ ksft_test_result_fail("futex_waitv private returned: %d %s\n",
|
|
+ res ? errno : res,
|
|
+ res ? strerror(errno) : "");
|
|
+ ret = RET_FAIL;
|
|
+ } else {
|
|
+ ksft_test_result_pass("futex_waitv invalid clockid\n");
|
|
+ }
|
|
+
|
|
+ ksft_print_cnts();
|
|
+ return ret;
|
|
+}
|
|
diff --git a/tools/testing/selftests/futex/functional/run.sh b/tools/testing/selftests/futex/functional/run.sh
|
|
index 11a9d6229..5ccd599da 100755
|
|
--- a/tools/testing/selftests/futex/functional/run.sh
|
|
+++ b/tools/testing/selftests/futex/functional/run.sh
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|
@@ -79,3 +79,6 @@ echo
|
|
|
|
echo
|
|
./futex_requeue $COLOR
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|
+
|
|
+echo
|
|
+./futex_waitv $COLOR
|
|
diff --git a/tools/testing/selftests/futex/include/futex2test.h b/tools/testing/selftests/futex/include/futex2test.h
|
|
new file mode 100644
|
|
index 000000000..9d305520e
|
|
--- /dev/null
|
|
+++ b/tools/testing/selftests/futex/include/futex2test.h
|
|
@@ -0,0 +1,22 @@
|
|
+/* SPDX-License-Identifier: GPL-2.0-or-later */
|
|
+/*
|
|
+ * Futex2 library addons for futex tests
|
|
+ *
|
|
+ * Copyright 2021 Collabora Ltd.
|
|
+ */
|
|
+#include <stdint.h>
|
|
+
|
|
+#define u64_to_ptr(x) ((void *)(uintptr_t)(x))
|
|
+
|
|
+/**
|
|
+ * futex_waitv - Wait at multiple futexes, wake on any
|
|
+ * @waiters: Array of waiters
|
|
+ * @nr_waiters: Length of waiters array
|
|
+ * @flags: Operation flags
|
|
+ * @timo: Optional timeout for operation
|
|
+ */
|
|
+static inline int futex_waitv(volatile struct futex_waitv *waiters, unsigned long nr_waiters,
|
|
+ unsigned long flags, struct timespec *timo, clockid_t clockid)
|
|
+{
|
|
+ return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, timo, clockid);
|
|
+}
|
|
--
|
|
2.33.1.711.g9d530dc002
|
|
|