From: Nick Piggin <nickpiggin@yahoo.com.au>
This actually does produce better code, especially under the locked
section.
Turns a conditional + unconditional jump under the lock in the unlikely
case into a cmov outside the lock.
---
25-akpm/kernel/sched.c | 9 +++++----
1 files changed, 5 insertions(+), 4 deletions(-)
diff -puN kernel/sched.c~sched-wake_up-speedup kernel/sched.c
--- 25/kernel/sched.c~sched-wake_up-speedup Mon Apr 26 15:31:46 2004
+++ 25-akpm/kernel/sched.c Mon Apr 26 15:31:46 2004
@@ -2400,15 +2400,16 @@ void fastcall __wake_up_locked(wait_queu
void fastcall __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
{
unsigned long flags;
+ int sync = 1;
if (unlikely(!q))
return;
+ if (unlikely(!nr_exclusive))
+ sync = 0;
+
spin_lock_irqsave(&q->lock, flags);
- if (likely(nr_exclusive))
- __wake_up_common(q, mode, nr_exclusive, 1);
- else
- __wake_up_common(q, mode, nr_exclusive, 0);
+ __wake_up_common(q, mode, nr_exclusive, sync);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
_