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locking/csd_lock: Use smp_cond_acquire() in csd_lock_wait()

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We can micro-optimize this call and mildly relax the
barrier requirements by relying on ctrl + rmb, keeping
the acquire semantics. In addition, this is pretty much
the now standard for busy-waiting under such restraints.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave@stgolabs.net
Link: http://lkml.kernel.org/r/1457574936-19065-3-git-send-email-dbueso@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Davidlohr Bueso 2016-03-09 17:55:36 -08:00 committed by Ingo Molnar
parent 90d1098478
commit 38460a2178
1 changed files with 1 additions and 2 deletions
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3
kernel/smp.c
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@ -107,8 +107,7 @@ void __init call_function_init(void)
*/
static __always_inline void csd_lock_wait(struct call_single_data *csd)
{
while (smp_load_acquire(&csd->flags) & CSD_FLAG_LOCK)
cpu_relax();
smp_cond_acquire(!(csd->flags & CSD_FLAG_LOCK));
}
static __always_inline void csd_lock(struct call_single_data *csd)