From: Ming Lei <ming.lei@redhat.com>
To: Bart Van Assche <Bart.VanAssche@wdc.com>
Cc: "jthumshirn@suse.de" <jthumshirn@suse.de>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"hch@lst.de" <hch@lst.de>,
"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
"axboe@kernel.dk" <axboe@kernel.dk>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
"hare@suse.com" <hare@suse.com>,
"jejb@linux.vnet.ibm.com" <jejb@linux.vnet.ibm.com>
Subject: Re: [PATCH] blk-mq: Fix several SCSI request queue lockups
Date: Tue, 5 Dec 2017 09:18:51 +0800 [thread overview]
Message-ID: <20171205011850.GD8365@ming.t460p> (raw)
In-Reply-To: <1512436422.2795.47.camel@wdc.com>
On Tue, Dec 05, 2017 at 01:13:43AM +0000, Bart Van Assche wrote:
> On Tue, 2017-12-05 at 09:04 +0800, Ming Lei wrote:
> > Then no reason to revert commit(0df21c86bdbf scsi: implement .get_budget an
> > .put_budget for blk-mq) for one issue which may never happen in reality since
> > this reproducer need out-of-tree patch.
>
> Sorry but I disagree completely. You seem to overlook that there may be other
> circumstances that trigger the same lockup, e.g. a SCSI queue full condition.
If the scsi_dev_queue_ready() returns false, .get_budget() catches that
and never add request to hctx->dispatch. And scsi_host_queue_ready()
always returns true, since we respect per-host queue depth by
blk_mq_get_driver_tag() before calling .queue_rq().
Or if I miss other cases, please point it out.
--
Ming
prev parent reply other threads:[~2017-12-05 1:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-04 17:30 [PATCH] blk-mq: Fix several SCSI request queue lockups Bart Van Assche
2017-12-04 22:42 ` Ming Lei
2017-12-04 22:48 ` Bart Van Assche
2017-12-04 23:01 ` Ming Lei
2017-12-04 23:32 ` Bart Van Assche
2017-12-05 0:20 ` Ming Lei
2017-12-05 0:29 ` Bart Van Assche
2017-12-05 1:04 ` Ming Lei
2017-12-05 1:13 ` Bart Van Assche
2017-12-05 1:18 ` Ming Lei [this message]
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