From: Bart Van Assche <Bart.VanAssche@wdc.com>
To: "snitzer@redhat.com" <snitzer@redhat.com>
Cc: "dm-devel@redhat.com" <dm-devel@redhat.com>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
"axboe@kernel.dk" <axboe@kernel.dk>
Subject: Re: [PATCH V4] blk-mq: introduce BLK_STS_DEV_RESOURCE
Date: Mon, 29 Jan 2018 21:51:55 +0000 [thread overview]
Message-ID: <1517262713.2687.56.camel@wdc.com> (raw)
In-Reply-To: <20180129214446.GD5744@redhat.com>
On Mon, 2018-01-29 at 16:44 -0500, Mike Snitzer wrote:
> But regardless of which wins the race, the queue will have been run.
> Which is all we care about right?
Running the queue is not sufficient. With this patch applied it can happen
that the block driver returns BLK_STS_DEV_RESOURCE, that the two or more
concurrent queue runs finish before sufficient device resources are available
to execute the request and that blk_mq_delay_run_hw_queue() does not get
called at all. If no other activity triggers a queue run, e.g. request
completion, this will result in a queue stall.
Bart.
next prev parent reply other threads:[~2018-01-29 21:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-29 20:33 [PATCH V4] blk-mq: introduce BLK_STS_DEV_RESOURCE Mike Snitzer
2018-01-29 21:22 ` Bart Van Assche
2018-01-29 21:44 ` Mike Snitzer
2018-01-29 21:51 ` Bart Van Assche [this message]
2018-01-29 22:14 ` Mike Snitzer
2018-01-29 22:22 ` Bart Van Assche
2018-01-30 5:55 ` Ming Lei
2018-01-30 3:20 ` Ming Lei
2018-02-02 0:26 ` [dm-devel] " John Stoffel
2018-02-02 0:53 ` Bart Van Assche
2018-01-30 3:16 ` Ming Lei
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