Greg Kroah-Hartman
598cf27219
Link: https://lore.kernel.org/r/20260217200002.683975158@linuxfoundation.org Tested-by: Florian Fainelli <florian.fainelli@broadcom.com> Tested-by: Takeshi Ogasawara <takeshi.ogasawara@futuring-girl.com> Tested-by: Peter Schneider <pschneider1968@googlemail.com> Tested-by: Jon Hunter <jonathanh@nvidia.com> Tested-by: Salvatore Bonaccorso <carnil@debian.org> Tested-by: Brett A C Sheffield <bacs@librecast.net> Tested-by: Mark Brown <broonie@kernel.org> Tested-by: Luna Jernberg <droidbittin@gmail.com> Tested-by: Ronald Warsow <rwarsow@gmx.de> Tested-by: Justin M. Forbes <jforbes@fedoraproject.org> Tested-by: Ron Economos <re@w6rz.net> Tested-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
49 lines
1.4 KiB
C
49 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
|
|
/*
|
|
* Resilient Queued Spin Lock defines
|
|
*
|
|
* (C) Copyright 2024-2025 Meta Platforms, Inc. and affiliates.
|
|
*
|
|
* Authors: Kumar Kartikeya Dwivedi <memxor@gmail.com>
|
|
*/
|
|
#ifndef __LINUX_RQSPINLOCK_H
|
|
#define __LINUX_RQSPINLOCK_H
|
|
|
|
#include "../locking/qspinlock.h"
|
|
|
|
/*
|
|
* try_cmpxchg_tail - Return result of cmpxchg of tail word with a new value
|
|
* @lock: Pointer to queued spinlock structure
|
|
* @tail: The tail to compare against
|
|
* @new_tail: The new queue tail code word
|
|
* Return: Bool to indicate whether the cmpxchg operation succeeded
|
|
*
|
|
* This is used by the head of the wait queue to clean up the queue.
|
|
* Provides relaxed ordering, since observers only rely on initialized
|
|
* state of the node which was made visible through the xchg_tail operation,
|
|
* i.e. through the smp_wmb preceding xchg_tail.
|
|
*
|
|
* We avoid using 16-bit cmpxchg, which is not available on all architectures.
|
|
*/
|
|
static __always_inline bool try_cmpxchg_tail(struct qspinlock *lock, u32 tail, u32 new_tail)
|
|
{
|
|
u32 old, new;
|
|
|
|
old = atomic_read(&lock->val);
|
|
do {
|
|
/*
|
|
* Is the tail part we compare to already stale? Fail.
|
|
*/
|
|
if ((old & _Q_TAIL_MASK) != tail)
|
|
return false;
|
|
/*
|
|
* Encode latest locked/pending state for new tail.
|
|
*/
|
|
new = (old & _Q_LOCKED_PENDING_MASK) | new_tail;
|
|
} while (!atomic_try_cmpxchg_relaxed(&lock->val, &old, new));
|
|
|
|
return true;
|
|
}
|
|
|
|
#endif /* __LINUX_RQSPINLOCK_H */
|