linux-kernel - Re: kernel BUG at kernel/sched/core.c:1465!

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Message-ID: <20120920171045.GC28934@google.com>
Date:	Thu, 20 Sep 2012 10:10:45 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Borislav Petkov <bp@...en8.de>,
	Michael Wang <wangyun@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Akinobu Mita <akinobu.mita@...il.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: kernel BUG at kernel/sched/core.c:1465!

Hello, guys.

On Thu, Sep 20, 2012 at 02:58:01PM +0200, Borislav Petkov wrote:
> commit c5c473e29c641380aef4a9d1f9c39de49219980f
> Merge: 925a6f0bf8bd 6889125b8b4e
> Author: Linus Torvalds <torvalds@...ux-foundation.org>
> Date:   Wed Sep 19 11:00:07 2012 -0700
> 
>     Merge branch 'for-3.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
>     
>     Pull workqueue / powernow-k8 fix from Tejun Heo:
>      "This is the fix for the bug where cpufreq/powernow-k8 was tripping
>       BUG_ON() in try_to_wake_up_local() by migrating workqueue worker to a
>       different CPU.
> 
> and this is exactly the same BUG_ON I'm hitting. and powernowk8_target
> is in the stack trace so it has to be the same issue.

Yeah, it's powernow-k8 migrating kworker to a different CPU.  It's
really curious that there are multiple reports of this in this cycle.
Nothing on workqueue side has changed and powernow-k8 has been broken
for very long time.  The only way this can get triggered is by
contending on fidvid_mutex in powernow-k8.  I suppose something
changed in such way that this happens with some regularity.  Have no
specific idea what.  Anyways, mainline should be okay now.

Thanks.

-- 
tejun
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