Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756758AbbLGWxv (ORCPT ); Mon, 7 Dec 2015 17:53:51 -0500 Received: from nautica.notk.org ([91.121.71.147]:47122 "EHLO nautica.notk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756331AbbLGWxt (ORCPT ); Mon, 7 Dec 2015 17:53:49 -0500 X-Greylist: delayed 409 seconds by postgrey-1.27 at vger.kernel.org; Mon, 07 Dec 2015 17:53:49 EST 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: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1314 Lines: 32 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/