From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756256Ab1CVPeu (ORCPT ); Tue, 22 Mar 2011 11:34:50 -0400 Received: from smtpbg55.qq.com ([64.71.138.44]:36309 "HELO smtpbg55.qq.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753239Ab1CVPer (ORCPT ); Tue, 22 Mar 2011 11:34:47 -0400 X-QQ-mid: esmtp10t1300807965t827t02904 X-QQ-SSF: 00000000000000F0FF300F000000000 Date: Tue, 22 Mar 2011 23:32:47 +0800 From: "Lina Lu" To: "Vivek Goyal" Cc: "linux kernel mailing list" References: <201103201523220468314@foxmail.com> Subject: Re: Re: cfq-iosched.c: panic in cfq_dispatch_requests Message-ID: <201103222332465003523@foxmail.com> X-mailer: Foxmail 6, 15, 201, 23 [cn] Mime-Version: 1.0 Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2011-03-21 22:08:19, Vivek Goyal wrote: >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? Hi Vivek Thanks for this patch! I did objdump and find place that divide by zero. It's in cfq_group_slice function, the st->total_weight is zero in my issue. As described in the patch, this is because I change the weight when the group on service tree. Thanks Lina > >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 @