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locking/barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()

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This new form allows using hardware assisted waiting.

Some hardware (ARM64 and x86) allow monitoring an address for changes,
so by providing a pointer we can use this to replace the cpu_relax()
with hardware optimized methods in the future.

Requested-by: Will Deacon <will.deacon@arm.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2016-04-04 10:57:12 +02:00 • committed by Ingo Molnar
parent 245050c287
commit 1f03e8d291
5 changed files with 31 additions and 18 deletions
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2
kernel/smp.c
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@ -107,7 +107,7 @@ void __init call_function_init(void)
*/
static __always_inline void csd_lock_wait(struct call_single_data *csd)
{
smp_cond_acquire(!(csd->flags & CSD_FLAG_LOCK));
smp_cond_load_acquire(&csd->flags, !(VAL & CSD_FLAG_LOCK));
}
static __always_inline void csd_lock(struct call_single_data *csd)