From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752943AbaBXSfK (ORCPT ); Mon, 24 Feb 2014 13:35:10 -0500 Received: from mail-qa0-f41.google.com ([209.85.216.41]:65432 "EHLO mail-qa0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752903AbaBXSfF (ORCPT ); Mon, 24 Feb 2014 13:35:05 -0500 Date: Mon, 24 Feb 2014 13:35:01 -0500 From: Tejun Heo To: "Jason J. Herne" Cc: Peter Zijlstra , Lai Jiangshan , linux-kernel@vger.kernel.org, Ingo Molnar Subject: Re: Subject: Warning in workqueue.c Message-ID: <20140224183501.GC2522@htj.dyndns.org> References: <20140207193604.GA8833@htj.dyndns.org> <52F8F0FB.3080206@linux.vnet.ibm.com> <20140210231742.GK25350@mtj.dyndns.org> <52FB90C6.4010701@linux.vnet.ibm.com> <52FC3C83.8020303@cn.fujitsu.com> <52FD07B2.5080402@linux.vnet.ibm.com> <20140213204102.GC17608@htj.dyndns.org> <20140214160923.GK27965@twins.programming.kicks-ass.net> <20140214162556.GF31544@htj.dyndns.org> <530B5EE3.8050200@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <530B5EE3.8050200@linux.vnet.ibm.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 Mon, Feb 24, 2014 at 10:01:55AM -0500, Jason J. Herne wrote: > On 02/14/2014 11:25 AM, Tejun Heo wrote: > >... > >Hmmm... weird, p's rq shouldn't have changed without its cpus_allowed > >busted. Anyways, let's wait for Jason's test results and see whether > >this is a regression at all. > > I was unable to determine exactly when this behavior was introduced. > The reason for this is because I keep hitting other bugs that > prevent the test case from running, the most notable of which causes > an immediate system hang. I also hit other warnings and bug messages > and I'm not sure if they are related or if they will influence the > probability of hitting the problem we are trying to solve here. > What I did find is the following: > > We hit this problem as far back as v3.10. > The warning was introduced after v3.5 but before v3.6. That's a bummer but it at least isn't a very new regression. Peter, any ideas on debugging this? I can make workqueue to play block / unblock dance to try to work around the issue but that'd be very yucky. It'd be great to root cause where the cpu selection anomaly is coming from. Thanks. -- tejun