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From: "Steve Wise" <swise@opengridcomputing.com>
To: "'Bart Van Assche'" <bart.vanassche@sandisk.com>,
        "'James Bottomley'" <jejb@linux.vnet.ibm.com>,
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In-Reply-To: <3fb86a78-de3a-b764-a493-cb5bc5b6d8b6@sandisk.com>
Subject: RE: [PATCH 9/9] [RFC] nvme: Fix a race condition
Date: Wed, 28 Sep 2016 09:23:03 -0500
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> 
> 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.