From: Ming Lei <ming.lei@redhat.com>
To: Keith Busch <keith.busch@linux.intel.com>
Cc: Christoph Hellwig <hch@lst.de>,
Keith Busch <keith.busch@intel.com>, Jens Axboe <axboe@kernel.dk>,
Bart Van Assche <bart.vanassche@wdc.com>,
linux-block@vger.kernel.org, linux-nvme@lists.infradead.org
Subject: Re: [RFC PATCH 3/3] blk-mq: Remove generation seqeunce
Date: Thu, 24 May 2018 09:52:30 +0800 [thread overview]
Message-ID: <20180524015229.GA15354@ming.t460p> (raw)
In-Reply-To: <20180523143539.GA10882@localhost.localdomain>
On Wed, May 23, 2018 at 08:35:40AM -0600, Keith Busch wrote:
> On Wed, May 23, 2018 at 08:34:48AM +0800, Ming Lei wrote:
> > Let's consider the normal NVMe timeout code path:
> >
> > 1) one request is timed out;
> >
> > 2) controller is shutdown, this timed-out request is requeued from
> > nvme_cancel_request(), but can't dispatch because queues are quiesced
> >
> > 3) reset is done from another context, and this request is dispatched
> > again, and completed exactly before returning EH_HANDLED to blk-mq, but
> > its state isn't updated to COMPLETE yet.
> >
> > 4) then double completions are done from both normal completion and timeout
> > path.
>
> We're definitely fixing this, but I must admit that's an impressive
> cognitive traversal across 5 thread contexts to arrive at that race. :)
It can be only 2 thread contexts if requeue is done on polled request
from nvme_timeout(), :-)
Thanks,
Ming
WARNING: multiple messages have this Message-ID (diff)
From: ming.lei@redhat.com (Ming Lei)
Subject: [RFC PATCH 3/3] blk-mq: Remove generation seqeunce
Date: Thu, 24 May 2018 09:52:30 +0800 [thread overview]
Message-ID: <20180524015229.GA15354@ming.t460p> (raw)
In-Reply-To: <20180523143539.GA10882@localhost.localdomain>
On Wed, May 23, 2018@08:35:40AM -0600, Keith Busch wrote:
> On Wed, May 23, 2018@08:34:48AM +0800, Ming Lei wrote:
> > Let's consider the normal NVMe timeout code path:
> >
> > 1) one request is timed out;
> >
> > 2) controller is shutdown, this timed-out request is requeued from
> > nvme_cancel_request(), but can't dispatch because queues are quiesced
> >
> > 3) reset is done from another context, and this request is dispatched
> > again, and completed exactly before returning EH_HANDLED to blk-mq, but
> > its state isn't updated to COMPLETE yet.
> >
> > 4) then double completions are done from both normal completion and timeout
> > path.
>
> We're definitely fixing this, but I must admit that's an impressive
> cognitive traversal across 5 thread contexts to arrive at that race. :)
It can be only 2 thread contexts if requeue is done on polled request
from nvme_timeout(), :-)
Thanks,
Ming
next prev parent reply other threads:[~2018-05-24 1:52 UTC|newest]
Thread overview: 128+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-21 23:11 [RFC PATCH 0/3] blk-mq: Timeout rework Keith Busch
2018-05-21 23:11 ` Keith Busch
2018-05-21 23:11 ` [RFC PATCH 1/3] blk-mq: Reference count request usage Keith Busch
2018-05-21 23:11 ` Keith Busch
2018-05-22 2:27 ` Ming Lei
2018-05-22 2:27 ` Ming Lei
2018-05-22 15:19 ` Christoph Hellwig
2018-05-22 15:19 ` Christoph Hellwig
2018-05-21 23:11 ` [RFC PATCH 2/3] blk-mq: Fix timeout and state order Keith Busch
2018-05-21 23:11 ` Keith Busch
2018-05-22 2:28 ` Ming Lei
2018-05-22 2:28 ` Ming Lei
2018-05-22 15:24 ` Christoph Hellwig
2018-05-22 15:24 ` Christoph Hellwig
2018-05-22 16:27 ` Bart Van Assche
2018-05-22 16:27 ` Bart Van Assche
2018-05-21 23:11 ` [RFC PATCH 3/3] blk-mq: Remove generation seqeunce Keith Busch
2018-05-21 23:11 ` Keith Busch
2018-05-21 23:29 ` Bart Van Assche
2018-05-21 23:29 ` Bart Van Assche
2018-05-22 14:15 ` Keith Busch
2018-05-22 14:15 ` Keith Busch
2018-05-22 16:29 ` Bart Van Assche
2018-05-22 16:29 ` Bart Van Assche
2018-05-22 16:34 ` Keith Busch
2018-05-22 16:34 ` Keith Busch
2018-05-22 16:48 ` Bart Van Assche
2018-05-22 16:48 ` Bart Van Assche
2018-05-22 2:49 ` Ming Lei
2018-05-22 2:49 ` Ming Lei
2018-05-22 3:16 ` Jens Axboe
2018-05-22 3:16 ` Jens Axboe
2018-05-22 3:47 ` Ming Lei
2018-05-22 3:47 ` Ming Lei
2018-05-22 3:51 ` Jens Axboe
2018-05-22 3:51 ` Jens Axboe
2018-05-22 8:51 ` Ming Lei
2018-05-22 8:51 ` Ming Lei
2018-05-22 14:35 ` Jens Axboe
2018-05-22 14:35 ` Jens Axboe
2018-05-22 14:20 ` Keith Busch
2018-05-22 14:20 ` Keith Busch
2018-05-22 14:37 ` Ming Lei
2018-05-22 14:37 ` Ming Lei
2018-05-22 14:46 ` Keith Busch
2018-05-22 14:46 ` Keith Busch
2018-05-22 14:57 ` Ming Lei
2018-05-22 14:57 ` Ming Lei
2018-05-22 15:01 ` Keith Busch
2018-05-22 15:01 ` Keith Busch
2018-05-22 15:07 ` Ming Lei
2018-05-22 15:07 ` Ming Lei
2018-05-22 15:17 ` Keith Busch
2018-05-22 15:17 ` Keith Busch
2018-05-22 15:23 ` Ming Lei
2018-05-22 15:23 ` Ming Lei
2018-05-22 16:17 ` Christoph Hellwig
2018-05-22 16:17 ` Christoph Hellwig
2018-05-23 0:34 ` Ming Lei
2018-05-23 0:34 ` Ming Lei
2018-05-23 14:35 ` Keith Busch
2018-05-23 14:35 ` Keith Busch
2018-05-24 1:52 ` Ming Lei [this message]
2018-05-24 1:52 ` Ming Lei
2018-05-23 5:48 ` Hannes Reinecke
2018-05-23 5:48 ` Hannes Reinecke
2018-07-12 18:16 ` Bart Van Assche
2018-07-12 18:16 ` Bart Van Assche
2018-07-12 19:24 ` Keith Busch
2018-07-12 19:24 ` Keith Busch
2018-07-12 22:24 ` Bart Van Assche
2018-07-12 22:24 ` Bart Van Assche
2018-07-13 1:12 ` jianchao.wang
2018-07-13 1:12 ` jianchao.wang
2018-07-13 2:40 ` jianchao.wang
2018-07-13 2:40 ` jianchao.wang
2018-07-13 15:43 ` Keith Busch
2018-07-13 15:43 ` Keith Busch
2018-07-13 15:52 ` Bart Van Assche
2018-07-13 15:52 ` Bart Van Assche
2018-07-13 18:47 ` Keith Busch
2018-07-13 18:47 ` Keith Busch
2018-07-13 23:03 ` Bart Van Assche
2018-07-13 23:03 ` Bart Van Assche
2018-07-13 23:58 ` Keith Busch
2018-07-13 23:58 ` Keith Busch
2018-07-18 19:56 ` hch
2018-07-18 19:56 ` hch
2018-07-18 20:39 ` hch
2018-07-18 20:39 ` hch
2018-07-18 21:05 ` Bart Van Assche
2018-07-18 21:05 ` Bart Van Assche
2018-07-18 22:53 ` Keith Busch
2018-07-18 22:53 ` Keith Busch
2018-07-18 20:53 ` Keith Busch
2018-07-18 20:53 ` Keith Busch
2018-07-18 20:58 ` Bart Van Assche
2018-07-18 20:58 ` Bart Van Assche
2018-07-18 21:17 ` Keith Busch
2018-07-18 21:17 ` Keith Busch
2018-07-18 21:30 ` Bart Van Assche
2018-07-18 21:30 ` Bart Van Assche
2018-07-18 21:33 ` Keith Busch
2018-07-18 21:33 ` Keith Busch
2018-07-19 13:19 ` hch
2018-07-19 13:19 ` hch
2018-07-19 14:59 ` Keith Busch
2018-07-19 14:59 ` Keith Busch
2018-07-19 15:56 ` Keith Busch
2018-07-19 15:56 ` Keith Busch
2018-07-19 16:04 ` Bart Van Assche
2018-07-19 16:04 ` Bart Van Assche
2018-07-19 16:22 ` Keith Busch
2018-07-19 16:22 ` Keith Busch
2018-07-19 16:29 ` hch
2018-07-19 16:29 ` hch
2018-07-19 20:18 ` Keith Busch
2018-07-19 20:18 ` Keith Busch
2018-07-19 13:22 ` hch
2018-07-19 13:22 ` hch
2018-05-21 23:29 ` [RFC PATCH 0/3] blk-mq: Timeout rework Bart Van Assche
2018-05-21 23:29 ` Bart Van Assche
2018-05-22 14:06 ` Keith Busch
2018-05-22 14:06 ` Keith Busch
2018-05-22 16:30 ` Bart Van Assche
2018-05-22 16:30 ` Bart Van Assche
2018-05-22 16:44 ` Keith Busch
2018-05-22 16:44 ` Keith Busch
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