linux-kernel - Re: [v3.10 regression] deadlock on cpu hotplug

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Message-ID: <51DCF982.4070707@linux.vnet.ibm.com>
Date:	Wed, 10 Jul 2013 14:04:50 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
CC:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
	Tomasz Figa <t.figa@...sung.com>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [v3.10 regression] deadlock on cpu hotplug

On 07/10/2013 01:39 PM, Viresh Kumar wrote:
> On 10 July 2013 09:42, Michael Wang <wangyun@...ux.vnet.ibm.com> wrote:
>> I'm not sure what is supposed after notify CPUFREQ_GOV_STOP event, if it
>> is in order to stop queued work and prevent follow work happen again,
>> then it failed to, and we need some method to stop queue work again when
>> CPUFREQ_GOV_STOP notified, like some flag in policy which will be
>> checked before re-queue work in work.
>>
>> But if the event is just to sync the queued work but not prevent follow
>> work happen, then things will become tough...we need confirm.
> 
> After GOV_STOP, until the time GOV_START is called, we shouldn't be
> queuing any work.

Thanks for the confirm :) seems like the root cause is very likely
related with the problem Srivatsa discovered.

I think the fix in his mail worth a try, but I need more investigations
to confirm that's the right way...

Regards,
Michael Wang

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