linux-kernel - Re: [RFC PATCH] blk-mq: fixup RESTART when queue becomes idle

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Date:   Thu, 18 Jan 2018 20:58:50 +0000
From:   Bart Van Assche <Bart.VanAssche@....com>
To:     "snitzer@...hat.com" <snitzer@...hat.com>,
        "axboe@...nel.dk" <axboe@...nel.dk>
CC:     "dm-devel@...hat.com" <dm-devel@...hat.com>,
        "hch@...radead.org" <hch@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "osandov@...com" <osandov@...com>,
        "ming.lei@...hat.com" <ming.lei@...hat.com>
Subject: Re: [RFC PATCH] blk-mq: fixup RESTART when queue becomes idle

On Thu, 2018-01-18 at 15:48 -0500, Mike Snitzer wrote:
> For Bart's test the underlying scsi-mq driver is what is regularly
> hitting this case in __blk_mq_try_issue_directly():
> 
>         if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))

Hello Mike,

That code path is not the code path that triggered the lockups that I reported
during the past days. These lockups were all triggered by incorrect handling of
.queue_rq() returning BLK_STS_RESOURCE.

Bart.