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

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 <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
kyagi · Mar 10, 2016 · 38460a2 · 38460a2
1 parent 90d1098
commit 38460a2
Showing 1 changed file with 1 addition and 2 deletions.
diff --git a/kernel/smp.c b/kernel/smp.c
@@ -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)