Merge tag 'locking-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Thomas Gleixner:

- Move futex code into kernel/futex/ and split up the kitche

Merge tag 'locking-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Thomas Gleixner:

- Move futex code into kernel/futex/ and split up the kitchen sink into
seperate files to make integration of sys_futex_waitv() simpler.

- Add a new sys_futex_waitv() syscall which allows to wait on multiple
futexes.

The main use case is emulating Windows' WaitForMultipleObjects which
allows Wine to improve the performance of Windows Games. Also native
Linux games can benefit from this interface as this is a common wait
pattern for this kind of applications.

- Add context to ww_mutex_trylock() to provide a path for i915 to
rework their eviction code step by step without making lockdep upset
until the final steps of rework are completed. It's also useful for
regulator and TTM to avoid dropping locks in the non contended path.

- Lockdep and might_sleep() cleanups and improvements

- A few improvements for the RT substitutions.

- The usual small improvements and cleanups.

* tag 'locking-core-2021-10-31' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
locking: Remove spin_lock_flags() etc
locking/rwsem: Fix comments about reader optimistic lock stealing conditions
locking: Remove rcu_read_{,un}lock() for preempt_{dis,en}able()
locking/rwsem: Disable preemption for spinning region
docs: futex: Fix kernel-doc references
futex: Fix PREEMPT_RT build
futex2: Documentation: Document sys_futex_waitv() uAPI
selftests: futex: Test sys_futex_waitv() wouldblock
selftests: futex: Test sys_futex_waitv() timeout
selftests: futex: Add sys_futex_waitv() test
futex,arm: Wire up sys_futex_waitv()
futex,x86: Wire up sys_futex_waitv()
futex: Implement sys_futex_waitv()
futex: Simplify double_lock_hb()
futex: Split out wait/wake
futex: Split out requeue
futex: Rename mark_wake_futex()
futex: Rename: match_futex()
futex: Rename: hb_waiter_{inc,dec,pending}()
futex: Split out PI futex
...

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futex: Implement sys_futex_waitv()

Add support to wait on multiple futexes. This is the interface
implemented by this syscall:

futex_waitv(struct futex_waitv *waiters, unsigned int nr_futexes,

futex: Implement sys_futex_waitv()

Add support to wait on multiple futexes. This is the interface
implemented by this syscall:

futex_waitv(struct futex_waitv *waiters, unsigned int nr_futexes,
unsigned int flags, struct timespec *timeout, clockid_t clockid)

struct futex_waitv {
__u64 val;
__u64 uaddr;
__u32 flags;
__u32 __reserved;
};

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
absolute timeout value for the operation. This syscall supports only
64bit sized timeout structs. The flags argument of the syscall should be
empty, but it can be used for future extensions. Flags for shared
futexes, sizes, etc. should be used on the individual flags of each
waiter.

__reserved is used for explicit padding and should be 0, but it might be
used for future extensions. If the userspace uses 32-bit pointers, it
should make sure to explicitly cast it when assigning to waitv::uaddr.

Returns the array index of one of the woken futexes. There’s no given
information of how many were woken, or any particular attribute of it
(if it’s the first woken, if it is of the smaller index...).

Signed-off-by: André Almeida <andrealmeid@collabora.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210923171111.300673-17-andrealmeid@collabora.com

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futex: Split out wait/wake

Move the wait/wake bits into their own file.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: André Almeida <andrealmeid@collabora.com>
Signed-

futex: Split out wait/wake

Move the wait/wake bits into their own file.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: André Almeida <andrealmeid@collabora.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: André Almeida <andrealmeid@collabora.com>
Link: https://lore.kernel.org/r/20210923171111.300673-15-andrealmeid@collabora.com

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