From: "Steve Wise" <swise@opengridcomputing.com>
To: "'Bart Van Assche'" <bart.vanassche@sandisk.com>,
"'James Bottomley'" <jejb@linux.vnet.ibm.com>,
"'Jens Axboe'" <axboe@fb.com>
Cc: <linux-block@vger.kernel.org>,
"'Martin K. Petersen'" <martin.petersen@oracle.com>,
"'Mike Snitzer'" <snitzer@redhat.com>,
<linux-rdma@vger.kernel.org>, <linux-nvme@lists.infradead.org>,
"'Keith Busch'" <keith.busch@intel.com>,
"'Doug Ledford'" <dledford@redhat.com>,
<linux-scsi@vger.kernel.org>, "'Christoph Hellwig'" <hch@lst.de>
Subject: RE: [PATCH 9/9] [RFC] nvme: Fix a race condition
Date: Wed, 28 Sep 2016 09:23:03 -0500 [thread overview]
Message-ID: <009601d21993$d2d33670$7879a350$@opengridcomputing.com> (raw)
In-Reply-To: <3fb86a78-de3a-b764-a493-cb5bc5b6d8b6@sandisk.com>
>
> Hello James and Steve,
>
> I will add a comment.
>
> Please note that the above patch does not change the behavior of
> nvme_stop_queues() except that it causes nvme_stop_queues() to wait
> until any ongoing nvme_queue_rq() calls have finished.
> blk_resume_queue() does not affect the value of the BLK_MQ_S_STOPPED bit
> that has been set by blk_mq_stop_hw_queues(). All it does is to resume
> pending blk_queue_enter() calls and to ensure that future
> blk_queue_enter() calls do not block. Even after blk_resume_queue() has
> been called if a new request is queued queue_rq() won't be invoked
> because the BLK_MQ_S_STOPPED bit is still set. Patch "dm: Fix a race
> condition related to stopping and starting queues" realizes a similar
> change in the dm driver and that change has been tested extensively.
>
Thanks for the detailed explanation! I think your code, then, is correct as-is. And this series doesn't fix the issue I'm hitting, so I'll keep digging. :)
Steve.
WARNING: multiple messages have this Message-ID (diff)
From: "Steve Wise" <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
To: 'Bart Van Assche'
<bart.vanassche-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>,
'James Bottomley'
<jejb-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
'Jens Axboe' <axboe-b10kYP2dOMg@public.gmane.org>
Cc: linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
"'Martin K. Petersen'"
<martin.petersen-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>,
'Mike Snitzer' <snitzer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
'Keith Busch'
<keith.busch-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
'Doug Ledford' <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
'Christoph Hellwig' <hch-jcswGhMUV9g@public.gmane.org>
Subject: RE: [PATCH 9/9] [RFC] nvme: Fix a race condition
Date: Wed, 28 Sep 2016 09:23:03 -0500 [thread overview]
Message-ID: <009601d21993$d2d33670$7879a350$@opengridcomputing.com> (raw)
In-Reply-To: <3fb86a78-de3a-b764-a493-cb5bc5b6d8b6-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>
>
> Hello James and Steve,
>
> I will add a comment.
>
> Please note that the above patch does not change the behavior of
> nvme_stop_queues() except that it causes nvme_stop_queues() to wait
> until any ongoing nvme_queue_rq() calls have finished.
> blk_resume_queue() does not affect the value of the BLK_MQ_S_STOPPED bit
> that has been set by blk_mq_stop_hw_queues(). All it does is to resume
> pending blk_queue_enter() calls and to ensure that future
> blk_queue_enter() calls do not block. Even after blk_resume_queue() has
> been called if a new request is queued queue_rq() won't be invoked
> because the BLK_MQ_S_STOPPED bit is still set. Patch "dm: Fix a race
> condition related to stopping and starting queues" realizes a similar
> change in the dm driver and that change has been tested extensively.
>
Thanks for the detailed explanation! I think your code, then, is correct as-is. And this series doesn't fix the issue I'm hitting, so I'll keep digging. :)
Steve.
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WARNING: multiple messages have this Message-ID (diff)
From: swise@opengridcomputing.com (Steve Wise)
Subject: [PATCH 9/9] [RFC] nvme: Fix a race condition
Date: Wed, 28 Sep 2016 09:23:03 -0500 [thread overview]
Message-ID: <009601d21993$d2d33670$7879a350$@opengridcomputing.com> (raw)
In-Reply-To: <3fb86a78-de3a-b764-a493-cb5bc5b6d8b6@sandisk.com>
>
> Hello James and Steve,
>
> I will add a comment.
>
> Please note that the above patch does not change the behavior of
> nvme_stop_queues() except that it causes nvme_stop_queues() to wait
> until any ongoing nvme_queue_rq() calls have finished.
> blk_resume_queue() does not affect the value of the BLK_MQ_S_STOPPED bit
> that has been set by blk_mq_stop_hw_queues(). All it does is to resume
> pending blk_queue_enter() calls and to ensure that future
> blk_queue_enter() calls do not block. Even after blk_resume_queue() has
> been called if a new request is queued queue_rq() won't be invoked
> because the BLK_MQ_S_STOPPED bit is still set. Patch "dm: Fix a race
> condition related to stopping and starting queues" realizes a similar
> change in the dm driver and that change has been tested extensively.
>
Thanks for the detailed explanation! I think your code, then, is correct as-is. And this series doesn't fix the issue I'm hitting, so I'll keep digging. :)
Steve.
next prev parent reply other threads:[~2016-09-28 14:23 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-26 18:25 [PATCH 0/9] Introduce blk_quiesce_queue() and blk_resume_queue() Bart Van Assche
2016-09-26 18:25 ` Bart Van Assche
2016-09-26 18:26 ` [PATCH 1/9] blk-mq: Introduce blk_mq_queue_stopped() Bart Van Assche
2016-09-26 18:26 ` Bart Van Assche
2016-09-26 18:26 ` Bart Van Assche
2016-09-27 6:20 ` Hannes Reinecke
2016-09-27 6:20 ` Hannes Reinecke
2016-09-27 7:38 ` Johannes Thumshirn
2016-09-27 7:38 ` Johannes Thumshirn
2016-09-27 7:38 ` Johannes Thumshirn
2016-09-26 18:26 ` [PATCH 2/9] dm: Fix a race condition related to stopping and starting queues Bart Van Assche
2016-09-26 18:26 ` Bart Van Assche
2016-09-27 6:21 ` Hannes Reinecke
2016-09-27 6:21 ` Hannes Reinecke
2016-09-27 6:21 ` Hannes Reinecke
2016-09-27 7:47 ` Johannes Thumshirn
2016-09-27 7:47 ` Johannes Thumshirn
2016-09-27 7:47 ` Johannes Thumshirn
2016-09-26 18:27 ` [PATCH 3/9] [RFC] nvme: Use BLK_MQ_S_STOPPED instead of QUEUE_FLAG_STOPPED in blk-mq code Bart Van Assche
2016-09-26 18:27 ` Bart Van Assche
2016-09-26 18:27 ` Bart Van Assche
2016-09-26 18:27 ` [PATCH 4/9] block: Move blk_freeze_queue() and blk_unfreeze_queue() code Bart Van Assche
2016-09-26 18:27 ` Bart Van Assche
2016-09-27 6:26 ` Hannes Reinecke
2016-09-27 6:26 ` Hannes Reinecke
2016-09-27 6:26 ` Hannes Reinecke
2016-09-27 7:52 ` Johannes Thumshirn
2016-09-27 7:52 ` Johannes Thumshirn
2016-09-27 7:52 ` Johannes Thumshirn
2016-09-26 18:27 ` [PATCH 5/9] block: Extend blk_freeze_queue_start() to the non-blk-mq path Bart Van Assche
2016-09-26 18:27 ` Bart Van Assche
2016-09-26 18:27 ` Bart Van Assche
2016-09-27 7:50 ` Johannes Thumshirn
2016-09-27 7:50 ` Johannes Thumshirn
2016-09-27 7:50 ` Johannes Thumshirn
2016-09-27 13:22 ` Ming Lei
2016-09-27 13:22 ` Ming Lei
2016-09-27 14:42 ` Bart Van Assche
2016-09-27 14:42 ` Bart Van Assche
2016-09-27 14:42 ` Bart Van Assche
2016-09-27 15:55 ` Bart Van Assche
2016-09-27 15:55 ` Bart Van Assche
2016-09-27 15:55 ` Bart Van Assche
2016-09-26 18:28 ` [PATCH 6/9] block: Rename mq_freeze_wq and mq_freeze_depth Bart Van Assche
2016-09-26 18:28 ` Bart Van Assche
2016-09-27 7:51 ` Johannes Thumshirn
2016-09-27 7:51 ` Johannes Thumshirn
2016-09-27 7:51 ` Johannes Thumshirn
2016-09-26 18:28 ` [PATCH 7/9] blk-mq: Introduce blk_quiesce_queue() and blk_resume_queue() Bart Van Assche
2016-09-26 18:28 ` Bart Van Assche
2016-09-26 18:28 ` [PATCH 8/9] SRP transport: Port srp_wait_for_queuecommand() to scsi-mq Bart Van Assche
2016-09-26 18:28 ` Bart Van Assche
2016-09-26 18:28 ` [PATCH 9/9] [RFC] nvme: Fix a race condition Bart Van Assche
2016-09-26 18:28 ` Bart Van Assche
2016-09-27 16:31 ` Steve Wise
2016-09-27 16:31 ` Steve Wise
2016-09-27 16:31 ` Steve Wise
2016-09-27 16:43 ` Bart Van Assche
2016-09-27 16:43 ` Bart Van Assche
2016-09-27 16:43 ` Bart Van Assche
2016-09-27 16:56 ` James Bottomley
2016-09-27 16:56 ` James Bottomley
2016-09-27 17:09 ` Bart Van Assche
2016-09-27 17:09 ` Bart Van Assche
2016-09-27 17:09 ` Bart Van Assche
2016-09-28 14:23 ` Steve Wise [this message]
2016-09-28 14:23 ` Steve Wise
2016-09-28 14:23 ` Steve Wise
2016-09-27 16:56 ` Steve Wise
2016-09-27 16:56 ` Steve Wise
2016-09-27 16:56 ` Steve Wise
2016-09-26 18:33 ` [PATCH 0/9] Introduce blk_quiesce_queue() and blk_resume_queue() Mike Snitzer
2016-09-26 18:33 ` Mike Snitzer
2016-09-26 18:33 ` Mike Snitzer
2016-09-26 18:46 ` Bart Van Assche
2016-09-26 18:46 ` Bart Van Assche
2016-09-26 18:46 ` Bart Van Assche
2016-09-26 22:26 ` Bart Van Assche
2016-09-26 22:26 ` Bart Van Assche
2016-09-26 22:26 ` Bart Van Assche
2016-10-11 16:27 ` Laurence Oberman
2016-10-11 16:27 ` Laurence Oberman
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