From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH 8/9] dm: Fix two race conditions related to stopping and starting queues Date: Thu, 1 Sep 2016 17:17:18 -0400 Message-ID: <20160901211718.GA12894@redhat.com> References: <20160901155051.GA11353@redhat.com> <20160901161253.GA11410@redhat.com> <20160901190505.GA12106@redhat.com> <235c0ca3-0c01-6dc8-208e-1a4c153dd69c@sandisk.com> <20160901203332.GB12407@redhat.com> <889bdb89-a16b-927a-adf0-fa04418a0c06@sandisk.com> <20160901204806.GA12742@redhat.com> <66e36ae7-19ff-058f-049a-3e91a62b19b3@sandisk.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <66e36ae7-19ff-058f-049a-3e91a62b19b3@sandisk.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Bart Van Assche Cc: "axboe@kernel.dk" , device-mapper development , "hch@lst.de" List-Id: dm-devel.ids On Thu, Sep 01 2016 at 4:52pm -0400, Bart Van Assche wrote: > On 09/01/2016 01:48 PM, Mike Snitzer wrote: > >Yeah, I since fixed that. Doesn't change the fact that your use of > >blk_mq_freeze_queue() causes the 100% cpu usage. > > Hello Mike, > > Sorry but that doesn't make sense to me. blk_mq_freeze_queue() > either returns quickly or waits. It cannot cause 100% CPU usage. > Something else must be going on. If you can make the code available > that you used in your test I will have a look at it. The suspend is hanging due the blk_mq_freeze_queue() -- and in turn the resume (after reinstating paths) never happens. So no paths are available. IO just keeps getting requeued, hence the 100% usage. The root of the problem is that the suspend isn't completing though. I've moved your work out to my private devel branch, see: http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/log/?h=devel