Commit e42986de authored Aug 15, 2012 by Joonsoo Kim Committed by Tejun Heo Aug 16, 2012

workqueue: change value of lcpu in __queue_delayed_work_on()



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>

parent b75cac93

kernel/workqueue.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -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;