linux-kernel - Re: [BUG] While changing the cpufreq governor, kernel hits a bug in workqueue.c

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Date:	Mon, 07 Jul 2008 15:18:07 +0530
From:	Nageswara R Sastry <rnsastry@...ux.vnet.ibm.com>
To:	Johannes Weiner <hannes@...urebad.de>
CC:	linux-kernel@...r.kernel.org, balbir@...ux.vnet.ibm.com,
	ego@...ux.vnet.ibm.com, svaidy@...ux.vnet.ibm.com,
	davej@...emonkey.org.uk
Subject: Re: [BUG] While changing the cpufreq governor, kernel hits a bug
 in workqueue.c

Hi Johannes,
>>> =======================================================
>>> [ INFO: possible circular locking dependency detected ]
>>> 2.6.25.7.cpufreq_patch #2
>>> -------------------------------------------------------
[...]
>> Okay, the problem is in cpufreq_conservative.c.  We
>> cancel_delayed_work_sync() while holding the mutex, but the work itself
>> tries to grab it and there it deadlocks; lockdep caught that right.
>>
>> The hunk for _ondemand is correct, but the one for _conservative is
>> obviously wrong, sorry :/
>>
>> I will whip something up and get back to you.  Thanks a lot for
>> testing!
> 
> Could you try the attached patch instead of the one above?
> 
> Dave, I dropped the mutex-grabbing from the conservative worker function
> as well as I don't see a reason for it, please correct me if I'm wrong.
> 
> 	Hannes
> 

The script is running now for more than 6 hours successfully, I will 
continue this and let you know if there are any failures.

* I am seeing the circular locking dependency with the above patch too.

Thanks!!
Regards
R.Nageswara Sastry
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