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