From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755015AbYHZBfj (ORCPT ); Mon, 25 Aug 2008 21:35:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753200AbYHZBfb (ORCPT ); Mon, 25 Aug 2008 21:35:31 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:46793 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751144AbYHZBfa (ORCPT ); Mon, 25 Aug 2008 21:35:30 -0400 Date: Mon, 25 Aug 2008 18:35:28 -0700 From: Andrew Morton To: Marc Haber Cc: "linux-kernel@vger.kernel.org" Subject: Re: 2.6.26.3 mount process looping on ext3 rw remount Message-Id: <20080825183528.30b66f45.akpm@linux-foundation.org> In-Reply-To: <20080823084228.GA21293@torres.zugschlus.de> References: <20080823084228.GA21293@torres.zugschlus.de> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 23 Aug 2008 10:42:28 +0200 Marc Haber wrote: > Hi, > > on my laptop, I am a heavy user of laptop-mode and suspend-to-disk. > Sometimes (maybe once out of ten), when disconnecting or connecting > external power, I have a mount process called by laptopmode busy > looping and taking all available CPU: > > ______acpid,4680 -c /etc/acpi/events > ___ ______lm_ac_adapter.s,29317 /etc/acpi/actions/lm_ac_adapter.sh > ___ ______laptop_mode,29318 /usr/sbin/laptop_mode auto > ___ ______laptop-mode,29386 /usr/share/laptop-mode-tools/modules/laptop-mode > ___ ______laptop-mode,29390 /usr/share/laptop-mode-tools/modules/laptop-mode > ___ ______laptop-mode,29409 /usr/share/laptop-mode-tools/modules/laptop-mode > ___ ______mount,29410 /dev/mapper/usr /mnt/usr -t ext3 -o remount,rw,commit=600 > > this is what top says > Cpu(s): 2.7%us, 96.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 1.3%hi, 0.0%si, 0.0%st > 29410 root 20 0 2068 684 564 R 92.7 0.0 87:37.71 mount > > The mount process does not react to SIGKILL, stracing the looping > process doesn't give any output, and the strace gets stuck and does > not react to Ctrl-C. A SIGKILL works for the strace process, though. > > To me as a layman this looks like the mount process gets stuck > somewhere in kernel land. I currently have the issue with 2.6.26.3. > > In the situation of plugging and/or unplugging the power, the notebook > used to completely freeze in the time when 2.6.24 and 2.6.25.$SMALL > were in use, with 2.6.25.$HIGH and 2.6.26 I haven't hat these freezes > any more. However, I am now plagued with the hanging mount processes. Yes, it's hung in the kernel. Please try to get a kernel profile while it's happening. oprofile maybe, or just the plain old timer-based profiler. There's some info in Documentation/basic_profiling.txt. > Any ideas? The profile will tell us where it got stuck. Actually, a simple alternative is to hit sysrq-P five or ten times. Most of the resulting stack traces will point back at where the CPU is stuck. This gets a bit hit-or-miss if you have multiple CPUs, because the sysrq-p trace can land on the wrong CPU. We recently added a sysrq-l which will generate a trace on all CPUS. I think we might recently have broken the sysrq output: some info which should be coming out isn't. Altering the logging priority (dmesg -n 7) might help with that.