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

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Message-ID: <CACVXFVP18pgz03LSwab-n2tKMAT15JmuF7Eh_O+q9TOHmhj2Qw@mail.gmail.com>
Date:	Fri, 19 Sep 2014 21:07:35 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Jens Axboe <axboe@...com>
Cc:	Christoph Hellwig <hch@....de>,
	James Bottomley <JBottomley@...allels.com>,
	Linux SCSI List <linux-scsi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Douglas Gilbert <dgilbert@...erlog.com>
Subject: Re: [PATCH] scsi-mq: fix hw queue hang caused by timeout

On Fri, Sep 19, 2014 at 1:03 AM, Jens Axboe <axboe@...com> wrote:
> 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.

Yeah, that looks better.

But it doesn't work after the simple change, and I need to
investigate further.

Thanks,
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