Re: [PATCH v4] blk-mq: Fix race conditions in request timeout handling

From: Bart Van Assche <bart.vanassche@wdc.com>
To: "tj@kernel.org" <tj@kernel.org>
Cc: "ming.lei@redhat.com" <ming.lei@redhat.com>,
	"hch@lst.de" <hch@lst.de>,
	"maxg@mellanox.com" <maxg@mellanox.com>,
	"israelr@mellanox.com" <israelr@mellanox.com>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"sagi@grimberg.me" <sagi@grimberg.me>,
	"axboe@kernel.dk" <axboe@kernel.dk>
Subject: Re: [PATCH v4] blk-mq: Fix race conditions in request timeout handling
Date: Wed, 18 Apr 2018 09:34:30 -0700	[thread overview]
Message-ID: <39a55c61-ea42-4131-0ed4-cfd357e133ce@wdc.com> (raw)
In-Reply-To: <20180410215456.GD793541@devbig577.frc2.facebook.com>

On 04/10/18 14:54, tj@kernel.org wrote:
> On Tue, Apr 10, 2018 at 09:46:23PM +0000, Bart Van Assche wrote:
>> On Tue, 2018-04-10 at 14:33 -0700, tj@kernel.org wrote:
>>> +       else
>>> +               rq->missed_completion = true;
>>
>> In this patch I found code that sets rq->missed_completion but no code that
>> clears it. Did I perhaps miss something?
> 
> Ah, yeah, I was moving it out of add_timer but forgot to actully add
> it to the issue path.  Fixed patch below.
> 
> BTW, no matter what we do w/ the request handover between normal and
> timeout paths, we'd need something similar.  Otherwise, while we can
> reduce the window, we can't get rid of it.
> 
> [ ... ]

Hello Tejun,

This patch no longer applies cleanly on Jens' tree. Can you rebase and 
repost it?

Thanks,

Bart.