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 <tj@xxxxxxxxxx> > 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 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
