Re: [PATCH] scsi-mq: fix hw queue hang caused by timeout

[Jens Axboe]

On 2014-09-18 10:35, Christoph Hellwig wrote:
> On Thu, Sep 18, 2014 at 11:59:10PM +0800, Ming Lei wrote:
> > If there are two requests or more timed out, the dispatch queue
> > is put into stopped state and never be recoverd, and there
> > is no such problem in non-mq mode.
> >
> > This patch trys to recover the stopped queue when the queue
> > becomes unbusy, then the following retries can move on.
> >
> > Basically this patch maintains same behavior for this situation
> > with non-mq mode.
>
> This looks somewhat similar to the issues that Doug reported, and I remember
> when he was last running into boot problems it was timeout related, too.
>
> As far as the implementation is concerned I think the correct fix is
> to clear the BLK_MQ_S_STOPPED queue flags in blk_mq_kick_requeue_list.

Since that's the kick part of the requeue, auto-starting the queue for 
that makes a lot of sense. I say that's the way we go.

--
Jens Axboe

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