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From: "tj@kernel.org" <tj@kernel.org>
To: Bart Van Assche <Bart.VanAssche@wdc.com>
Cc: "hch@lst.de" <hch@lst.de>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"axboe@kernel.dk" <axboe@kernel.dk>
Subject: Re: [PATCH v2] blk-mq: Fix race between resetting the timer and completion handling
Date: Wed, 7 Feb 2018 12:09:51 -0800	[thread overview]
Message-ID: <20180207200951.GE695913@devbig577.frc2.facebook.com> (raw)
In-Reply-To: <1518030233.2870.57.camel@wdc.com>

Hello,

On Wed, Feb 07, 2018 at 07:03:56PM +0000, Bart Van Assche wrote:
> I tried the above patch but already during the first iteration of the test I
> noticed that the test hung, probably due to the following request that got stuck:
> 
> $ (cd /sys/kernel/debug/block && grep -aH . */*/*/rq_list)
> 00000000a98cff60 {.op=SCSI_IN, .cmd_flags=, .rq_flags=MQ_INFLIGHT|PREEMPT|QUIET|IO_STAT|PM,
>  .state=idle, .tag=22, .internal_tag=-1, .cmd=Synchronize Cache(10) 35 00 00 00 00 00, .retries=0,
>  .result = 0x0, .flags=TAGGED, .timeout=60.000, allocated 872.690 s ago}

I'm wonder how this happened, so we can lose a completion when it
races against BLK_EH_RESET_TIMER; however, the command should timeout
later cuz the timer is running again now.  Maybe we actually had the
memory barrier race that you pointed out in the other message?

Thanks.

-- 
tejun

  reply	other threads:[~2018-02-07 20:09 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-07  1:11 [PATCH v2] blk-mq: Fix race between resetting the timer and completion handling Bart Van Assche
2018-02-07 17:06 ` Tejun Heo
2018-02-07 17:27   ` Bart Van Assche
2018-02-07 17:35     ` tj
2018-02-07 18:14       ` Bart Van Assche
2018-02-07 20:07         ` tj
2018-02-07 23:48           ` Bart Van Assche
2018-02-08  1:09             ` Bart Van Assche
2018-02-08 15:39               ` tj
2018-02-08 15:40                 ` tj
2018-02-08 16:31                 ` Bart Van Assche
2018-02-08 17:00                   ` tj
2018-02-08 17:10                     ` Bart Van Assche
2018-02-08 17:19                       ` tj
2018-02-08 17:37                         ` Bart Van Assche
2018-02-08 17:40                           ` tj
2018-02-08 17:48                             ` Bart Van Assche
2018-02-08 17:54                               ` tj
2018-02-13 21:20                   ` tj
2018-02-14 16:58                     ` Bart Van Assche
2018-02-18 13:11                       ` tj
2018-02-21 18:53                         ` Bart Van Assche
2018-02-21 19:21                           ` tj
2018-02-21 22:55                             ` Bart Van Assche
2018-02-07 19:03   ` Bart Van Assche
2018-02-07 20:09     ` tj [this message]
2018-02-07 21:02       ` Bart Van Assche
2018-02-07 21:40         ` tj

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