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

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Message-ID: <20170524102500.GA26375@dhcp-216.srv.tuxera.com>
Date:   Wed, 24 May 2017 13:25:00 +0300
From:   Rakesh Pandit <rakesh@...era.com>
To:     Christoph Hellwig <hch@....de>
CC:     <linux-nvme@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        Keith Busch <keith.busch@...el.com>, Jens Axboe <axboe@...com>,
        Sagi Grimberg <sagi@...mberg.me>
Subject: Re: [PATCH 1/2] nvme: fix multiple ctrl removal scheduling

On Wed, May 24, 2017 at 11:37:55AM +0200, Christoph Hellwig wrote:
> 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

Thanks, right.

> 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?

Sure, will post it in next version.