Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754601Ab2JRI1P (ORCPT ); Thu, 18 Oct 2012 04:27:15 -0400 Received: from mail-da0-f46.google.com ([209.85.210.46]:39900 "EHLO mail-da0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752602Ab2JRI1L (ORCPT ); Thu, 18 Oct 2012 04:27:11 -0400 MIME-Version: 1.0 In-Reply-To: References: <1340364965.18025.71.camel@twins> Date: Thu, 18 Oct 2012 02:27:10 -0600 X-Google-Sender-Auth: N7XPkScFupdNgq_0mqBVpjw2FtI Message-ID: Subject: Re: [tip:sched/core] sched: Fix race in task_group() From: cwillu To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, peterz@infradead.org, tglx@linutronix.de, stefan.bader@canonical.com Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1814 Lines: 42 On Tue, Jul 24, 2012 at 8:21 AM, tip-bot for Peter Zijlstra wrote: > Commit-ID: 8323f26ce3425460769605a6aece7a174edaa7d1 > Gitweb: http://git.kernel.org/tip/8323f26ce3425460769605a6aece7a174edaa7d1 > Author: Peter Zijlstra > AuthorDate: Fri, 22 Jun 2012 13:36:05 +0200 > Committer: Ingo Molnar > CommitDate: Tue, 24 Jul 2012 13:58:20 +0200 > > sched: Fix race in task_group() > > Stefan reported a crash on a kernel before a3e5d1091c1 ("sched: > Don't call task_group() too many times in set_task_rq()"), he > found the reason to be that the multiple task_group() > invocations in set_task_rq() returned different values. > > Looking at all that I found a lack of serialization and plain > wrong comments. > > The below tries to fix it using an extra pointer which is > updated under the appropriate scheduler locks. Its not pretty, > but I can't really see another way given how all the cgroup > stuff works. > > Reported-and-tested-by: Stefan Bader > Signed-off-by: Peter Zijlstra > Link: http://lkml.kernel.org/r/1340364965.18025.71.camel@twins > Signed-off-by: Ingo Molnar I just finished bisecting a crash on boot to this commit; booting with "noautogroup" brings it back. 3.5.4 is the latest -stable that still boots, and none of the 3.6 rc's boot at all. Photo of the bug (3.6.0next is 3.6 + btrfs's for-linus): https://lh5.googleusercontent.com/-0DY-YYhgvzs/UHdB-BQdzMI/AAAAAAAAAEg/QhY9rgxnv98/s811/2012-10-11 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/