Commit 25de0902 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds

[PATCH] sched: micro-optimisation for wake_up

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.
parent 85841fc0
...@@ -2400,15 +2400,16 @@ void fastcall __wake_up_locked(wait_queue_head_t *q, unsigned int mode) ...@@ -2400,15 +2400,16 @@ void fastcall __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
void fastcall __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive) void fastcall __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
{ {
unsigned long flags; unsigned long flags;
int sync = 1;
if (unlikely(!q)) if (unlikely(!q))
return; return;
if (unlikely(!nr_exclusive))
sync = 0;
spin_lock_irqsave(&q->lock, flags); spin_lock_irqsave(&q->lock, flags);
if (likely(nr_exclusive)) __wake_up_common(q, mode, nr_exclusive, sync);
__wake_up_common(q, mode, nr_exclusive, 1);
else
__wake_up_common(q, mode, nr_exclusive, 0);
spin_unlock_irqrestore(&q->lock, flags); spin_unlock_irqrestore(&q->lock, flags);
} }
EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */ EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
......
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