locking/barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()
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>
diff --git a/kernel/smp.c b/kernel/smp.c
index 7416544..36552be 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -107,7 +107,7 @@
*/
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)