linux-kernel - Re: [PATCH 1/2] nvme: fix multiple ctrl removal scheduling

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Message-ID: <20170524093755.GA17483@lst.de>
Date:   Wed, 24 May 2017 11:37:55 +0200
From:   Christoph Hellwig <hch@....de>
To:     Rakesh Pandit <rakesh@...era.com>
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Keith Busch <keith.busch@...el.com>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>
Subject: Re: [PATCH 1/2] nvme: fix multiple ctrl removal scheduling

On Wed, May 24, 2017 at 01:15:47AM +0300, Rakesh Pandit wrote:
> Commit c5f6ce97c1210 tries to address multiple resets but fails as
> work_busy doesn't involve any synchronization and can fail.  This is
> reproducible easily as can be seen by WARNING below which is triggered
> with line:
> 
> WARN_ON(dev->ctrl.state == NVME_CTRL_RESETTING)
> 
> Allowing multiple resets can result in multiple controller removal as
> well if different conditions inside nvme_reset_work fail and which
> might deadlock on device_release_driver.
> 
> This patch addresses the problem by using state of controller to
> decide whether reset should be queued or not as state change is
> synchronizated using controller spinlock.

But we don't hold the lock over the check and the decision.  I suspect
what we need to do is to actually change to the resetting state
before queueing up the reset work.  Can you give that a spin?