From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: virt_blk BUG: sleeping function called from invalid context Date: Sun, 29 Jun 2014 14:55:36 -0600 Message-ID: <53B07D48.60003@kernel.dk> References: <20140629082637.GA23942@redhat.com> <20140629193222.GA7030@lst.de> <20140629204710.GB11100@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140629204710.GB11100@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" , Christoph Hellwig Cc: Josh Boyer , Robert Love , Greg Kroah-Hartman , "Linux-Kernel@Vger. Kernel. Org" , virtualization@lists.linux-foundation.org, Tejun Heo , Eric Paris , Brian Lane , John McCutchan List-Id: virtualization@lists.linuxfoundation.org On 06/29/2014 02:47 PM, Michael S. Tsirkin wrote: > On Sun, Jun 29, 2014 at 09:32:22PM +0200, Christoph Hellwig wrote: >> On Sun, Jun 29, 2014 at 11:26:37AM +0300, Michael S. Tsirkin wrote: >>> On Fri, Jun 27, 2014 at 07:57:38AM -0400, Josh Boyer wrote: >>>> Hi All, >>>> >>>> We've had a report[1] of the virt_blk driver causing a lot of spew >>>> because it's calling a sleeping function from an invalid context. The >>>> backtrace is below. This is with kernel v3.16-rc2-69-gd91d66e88ea9. >>> >>> Hi Jens, pls see below - it looks like the call to blk_mq_end_io >>> from IRQ context is causing the issue. >>> IIUC you switched virtio to this from __blk_end_request_all in >>> >>> commit 1cf7e9c68fe84248174e998922b39e508375e7c1 >>> virtio_blk: blk-mq support >>> >>> Is this always safe? >>> I note that at least one other driver is doing this: >>> drivers/block/mtip32xx/mtip32xx.c >> >> Just like __blk_end_request_all blk_mq_end_io is supposed to be called >> from irq context. The problem is that the MD bio end_io handler is calling >> a sleeping function. Not sure if that's a bug in MD though given the >> kernfs symbols in the all trace and the recent churn in that area. > > My understanding is this: > > bitmap_endwrite -> calls sysfs_notify_dirent_safe under spinlock > -> calls kernfs_notify which takes a mutex. > > So I am guessing it is this commit: > > commit d911d98748018f7c8facc035ba39c30f5cce6f9c > Author: Tejun Heo > Date: Wed Apr 9 11:07:31 2014 -0400 > > kernfs: make kernfs_notify() trigger inotify events too > > Tejun, what do you think? > > Josh, Brian, could you try reverting that commit to see if it helps? That definitely be a bug. If you need to block off ->bi_end_io(), just must punt to a worker thread. -- Jens Axboe