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workqueue: change value of lcpu in __queue_delayed_work_on()

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We assign cpu id into work struct's data field in __queue_delayed_work_on().
In current implementation, when work is come in first time,
current running cpu id is assigned.
If we do __queue_delayed_work_on() with CPU A on CPU B,
__queue_work() invoked in delayed_work_timer_fn() go into
the following sub-optimal path in case of WQ_NON_REENTRANT.

	gcwq = get_gcwq(cpu);
	if (wq->flags & WQ_NON_REENTRANT &&
		(last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) {

Change lcpu to @cpu and rechange lcpu to local cpu if lcpu is WORK_CPU_UNBOUND.
It is sufficient to prevent to go into sub-optimal path.

tj: Slightly rephrased the comment.

Signed-off-by: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Joonsoo Kim 2012-08-15 23:25:38 +09:00 committed by Tejun Heo
parent b75cac9368
commit e42986de48
1 changed files with 8 additions and 2 deletions
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10
kernel/workqueue.c
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@ -1356,9 +1356,15 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
if (!(wq->flags & WQ_UNBOUND)) {
struct global_cwq *gcwq = get_work_gcwq(work);
if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND)
/*
* If we cannot get the last gcwq from @work directly,
* select the last CPU such that it avoids unnecessarily
* triggering non-reentrancy check in __queue_work().
*/
lcpu = cpu;
if (gcwq)
lcpu = gcwq->cpu;
else
if (lcpu == WORK_CPU_UNBOUND)
lcpu = raw_smp_processor_id();
} else {
lcpu = WORK_CPU_UNBOUND;