From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753391Ab1CUOIY (ORCPT ); Mon, 21 Mar 2011 10:08:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:8308 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752193Ab1CUOIW (ORCPT ); Mon, 21 Mar 2011 10:08:22 -0400 Date: Mon, 21 Mar 2011 10:07:37 -0400 From: Vivek Goyal To: Lina Lu Cc: linux kernel mailing list Subject: Re: cfq-iosched.c: panic in cfq_dispatch_requests Message-ID: <20110321140737.GA2694@redhat.com> References: <201103201523220468314@foxmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201103201523220468314@foxmail.com> 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 On Sun, Mar 20, 2011 at 03:23:23PM +0800, Lina Lu wrote: > Hi Vivek, > > I did some test with blkio weight policy these days. The kernel panic > once in a while. > > >From the calltrace, It 's in func cfq_dispatch_requests(+0x058D). > And I caught a divide by zero error with system monitor tools. Hi Lina, Can you please paste the full backtrace here. > > The panic happens when I first set 100 weight to two IO pids, then > change the weight to 200, and begin to perform IO. The kernel panic > accurately when the IO begin. So you notice this only if weights are changed otherwise not? Recently Justin fixed a bug in CFQ where crash can happen when weights are changed. This fix in Jens's block tree. Can you please apply this patch and see if it resolves your issue too. commit 8184f93eced1e304721c2a55c00d87d5a14f8907 Author: Justin TerAvest Date: Thu Mar 17 16:12:36 2011 +0100 cfq-iosched: Don't update group weights when on service tree Thanks Vivek