Re: [PATCH] block: Avoid missed wakeup in request waitqueue

[Asias He]

On 05/28/2012 06:26 PM, Tejun Heo wrote:
> On Mon, May 28, 2012 at 12:19:03PM +0800, Asias He wrote:
> > diff --git a/block/blk-core.c b/block/blk-core.c
> > index 1f61b74..1a45877 100644
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -359,9 +359,10 @@ EXPORT_SYMBOL(blk_put_queue);
> >    */
> >   void blk_drain_queue(struct request_queue *q, bool drain_all)
> >   {
> > +	int i;
> > +
> >   	while (true) {
> >   		bool drain = false;
> > -		int i;
> >
> >   		spin_lock_irq(q->queue_lock);
> >
> > @@ -400,6 +401,14 @@ void blk_drain_queue(struct request_queue *q, bool drain_all)
> >   			break;
> >   		msleep(10);
> >   	}
> > +
> > +	/* Wake up threads which are sleeping on get_request() */
> > +	spin_lock_irq(q->queue_lock);
> > +	for (i = 0; i<  ARRAY_SIZE(q->rq.wait); i++) {
> > +		if (waitqueue_active(&q->rq.wait[i]))
> > +			wake_up_all(&q->rq.wait[i]);
> > +	}
> > +	spin_unlock_irq(q->queue_lock);
>
> I don't think we need waitqueue_active() optimization here.  Let's
> just do,
>
> 	/* please explain why this is necessary */
> 	for (i = 0; i<  ARRAY_SIZE(q->rq.wait); i++)
> 		wake_up_all(&q->rq.wait[i]);

OK. V2 is on its way.


--
Asias
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