From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932135Ab1CVPjy (ORCPT ); Tue, 22 Mar 2011 11:39:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56440 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756269Ab1CVPjw (ORCPT ); Tue, 22 Mar 2011 11:39:52 -0400 Date: Tue, 22 Mar 2011 11:39:27 -0400 From: Vivek Goyal To: Lina Lu Cc: linux kernel mailing list Subject: Re: Re: cfq-iosched.c: panic in cfq_dispatch_requests Message-ID: <20110322153927.GF3757@redhat.com> References: <201103201523220468314@foxmail.com> <201103222332465003523@foxmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201103222332465003523@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 Tue, Mar 22, 2011 at 11:32:47PM +0800, Lina Lu wrote: > 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. Ok, so this patch did solve the issue you are facing? Thanks Vivek