linux-kernel - Re: Soft lockup during suspend since ~2.6.36 [bisected]

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Date:	Tue, 5 Apr 2011 20:56:56 +0200
From:	Thilo-Alexander Ginkel <thilo@...kel.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: Soft lockup during suspend since ~2.6.36 [bisected]

On Mon, Apr 4, 2011 at 17:32, Arnd Bergmann <arnd@...db.de> wrote:
> On Monday 04 April 2011, Thilo-Alexander Ginkel wrote:
>> ACK. I see two possibilities:
>> a) The bug was introduced after the bisected bug was fixed
>> b) The bug was already present earlier, but was masked by the bug from
>> the bisected change
>>
>> I hope for a) as that would open the possibility to bisect this new bug.
>
> In case of b), you can still bisect it when you either apply the later fix
> or revert the original patch whenever you build a kernel. Or you can try
> to avoid using the usb-hid driver during bisect.

Thanks, that worked pretty well. A bisect with eleven builds later I
have now identified the following candidate commit, which may have
introduced the bug:

dcd989cb73ab0f7b722d64ab6516f101d9f43f88 is the first bad commit
commit dcd989cb73ab0f7b722d64ab6516f101d9f43f88
Author: Tejun Heo <tj@...nel.org>
Date:   Tue Jun 29 10:07:14 2010 +0200

    workqueue: implement several utility APIs

    Implement the following utility APIs.

     workqueue_set_max_active() : adjust max_active of a wq
     workqueue_congested()              : test whether a wq is contested
     work_cpu()                 : determine the last / current cpu of a work
     work_busy()                        : query whether a work is busy

    * Anton Blanchard fixed missing ret initialization in work_busy().

    Signed-off-by: Tejun Heo <tj@...nel.org>
    Cc: Anton Blanchard <anton@...ba.org>

:040000 040000 8b7443c650f0af36f1deba560586a91f6a88abcc
065589a95857a2fb73b94dc242c50ba558179a2a M      include
:040000 040000 84ca2de78af16483fa60a423f4f2d6eee0279eed
27487850f11a1e7ee9e4eaac54fd88f16d420d47 M      kernel

Brief summary for Tejun: Starting with this commit my system (x86_64,
4 CPUs) sporadically (probability around 25%) fails to suspend due to
a soft lockup. Full details at:
  https://lkml.org/lkml/2011/4/4/116
or:
  <BANLkTi=n4jLsjOYCd0L3hYb30sgPmdv_WA@...l.gmail.com>

I'd appreciate your help to resolve this issue and would be glad to
test any candidate patches.

Thanks,
Thilo
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