From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 7 Dec 2015 23:46:43 +0100 From: Dominique Martinet To: Andy Lutomirski Cc: "linux-kernel@vger.kernel.org" , V9FS Developers , Linux FS Devel Subject: Re: [V9fs-developer] Hang triggered by udev coldplug, looks like a race Message-ID: <20151207224643.GA10531@nautica> References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: Andy Lutomirski wrote on Mon, Dec 07, 2015: > On Thu, Dec 3, 2015 at 9:52 PM, Andy Lutomirski wrote: > > Sometimes udevadm trigger --action=add hangs the system, and the splat > > below happens. This seems to be timing dependent, and I haven't been > > able to trigger it yet with lockdep enabled, sadly. > > > > Any ideas? I not, I'll try to instrument it better tomorrow. > > More details: this is caused by a storm of /sbin/hotplug UMH calls > (yes, misconfigured kernel, but still). /sbin is a symlink to > /usr/sbin, /usr/sbin/hotplug doesn't exist, and all of the above is on > rootfs, which is 9p over virtio. > > Pointing uevent_helper at /usr/sbin/hotplug (which still doesn't > exist) seems to work around it. Can you reproduce it on a booted system with something like `seq 1 1000000 | xargs -P 1024 -I{} cat /sbin/foo >&/dev/null` ? (trying execs might be closer to your workload, not sure how much this or using umh might change) Also, what qemu version please just to try to match your environment ? -- Dominique Martinet