From mboxrd@z Thu Jan  1 00:00:00 1970
From: keith.busch@linux.intel.com (Keith Busch)
Date: Fri, 25 May 2018 08:22:34 -0600
Subject: [PATCHv3 1/9] nvme: Sync request queues on reset
In-Reply-To: <20180525124209.GD23463@lst.de>
References: <20180524203500.14081-1-keith.busch@intel.com>
 <20180524203500.14081-2-keith.busch@intel.com>
 <20180525124209.GD23463@lst.de>
Message-ID: <20180525142233.GN11037@localhost.localdomain>

On Fri, May 25, 2018@02:42:09PM +0200, Christoph Hellwig wrote:
> On Thu, May 24, 2018@02:34:52PM -0600, Keith Busch wrote:
> > This patch fixes races that occur with simultaneous controller
> > resets
> 
> Wait..  How do we end up with simultaneous controller resets?  We
> not only have the NVME_CTRL_RESETTING resetting state, but also
> execute all resets from ctrl->reset_work, so they are implicitly
> single threaded.

Right, the bring up is single threaded, but the NVMe Controller Level
Reset (CC.EN 1 -> 0) can happen through a timeout. This patch is really
just working with the way blk-mq's timeout handler claims requests
and prevents the driver from completing them. The reset_work operates
under the assumption that there are no outstanding commands after
nvme_dev_disable, so this patch just ensures that's the case.