Messages in this thread | | | Subject | Re: question about blk_schedule_flush_plug | From | Mike Galbraith <> | Date | Mon, 23 May 2011 09:43:49 +0200 |
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On Mon, 2011-05-23 at 17:05 +1000, Con Kolivas wrote: > I was looking at the scheduler changes going into 2.6.39 again and wondered > about the use of blk_schedule_flush_plug smack in the middle of schedule() > > It looks like this: > if (blk_needs_flush_plug(prev)) { > raw_spin_unlock(&rq->lock); > blk_schedule_flush_plug(prev); > raw_spin_lock(&rq->lock); > } > > Now call me suspicious but to my eyes it looks really dubious unlocking the > runqueue like that right in the heart of schedule(). > > Comments?
Releasing/retaking rq->lock is nothing new:
static void idle_balance(int this_cpu, struct rq *this_rq) { ... /* * Drop the rq->lock, but keep IRQ/preempt disabled. */ raw_spin_unlock(&this_rq->lock);
See also need_resched, and double_lock_balance() instances.
-Mike
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