Commit 6631e635 authored Apr 13, 2011 by Linus Torvalds

block: don't flush plugged IO on forced preemtion scheduling



We really only want to unplug the pending IO when the process actually
goes to sleep.  So move the test for flushing the plug up to the place
where we actually deactivate the task - where we have properly checked
for preemption and for the process really sleeping.

Acked-by: Jens Axboe <jaxboe@fusionio.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a626ca6a

kernel/sched.c

+10 −10

Original line number	Diff line number	Diff line
		@@ -4111,19 +4111,19 @@ need_resched:
		try_to_wake_up_local(to_wakeup);
		}
		deactivate_task(rq, prev, DEQUEUE_SLEEP);
		}
		switch_count = &prev->nvcsw;
		}

		/*
		* If we are going to sleep and we have plugged IO queued, make
		* sure to submit it to avoid deadlocks.
		*/
		if (prev->state != TASK_RUNNING && blk_needs_flush_plug(prev)) {
		if (blk_needs_flush_plug(prev)) {
		raw_spin_unlock(&rq->lock);
		blk_flush_plug(prev);
		raw_spin_lock(&rq->lock);
		}
		}
		switch_count = &prev->nvcsw;
		}

		pre_schedule(rq, prev);

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