From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751236Ab1AWQPJ (ORCPT ); Sun, 23 Jan 2011 11:15:09 -0500 Received: from ns.km10614-05.keymachine.de ([87.118.102.170]:55327 "EHLO km10614-05.keymachine.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750981Ab1AWQPI (ORCPT ); Sun, 23 Jan 2011 11:15:08 -0500 Date: Sun, 23 Jan 2011 17:15:00 +0100 From: Harald Braumann To: linux-kernel@vger.kernel.org Subject: Re: Deadlock on concurrent remount-ro and mdadm --stop (2.6.37) Message-ID: <20110123161500.GB4108@nn.nn> Mail-Followup-To: Harald Braumann , linux-kernel@vger.kernel.org References: <20110121124754.GA5233@nn.nn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110121124754.GA5233@nn.nn> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 21, 2011 at 01:47:54PM +0100, Harald Braumann wrote: > On shutdown `umountroot' and `mdadm-raid' are executed concurrently. The > actual commands are: > mount -o remount,ro / > mdadm --stop --scan > > This seems to trigger a deadlock in the kernel. Dumping blocked tasks (sysrq-W) > gives: > > md126_raid5: call trace: > md_super_wait > autoremove_wake_function > bitmap_unplug > ... > > mount: call trace: > sync_page > io_schedule > sync_page I've now disable parallel boot in my system, so umountroot and mdadm shouldn't be called cuncurrently anymore. But I still get lock-ups on mdadm --stop. Umountroot is called before mdadm --stop, and all other filesystems are unmounted before that, so I guess there should be no `sync_page' in progress anymore. But I also have swap on the raid, so maybe there's a problem? As not even the magic SysRQ keys work, I can't provide any more details. Any suggestions how I could debug this problem? Cheers, harry