linux-kernel - Re: [PATCH] cpufreq, store_scaling_governor requires policy->rwsem to be held for duration of changing governors [v2]

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Message-ID: <53DA8389.80804@redhat.com>
Date:	Thu, 31 Jul 2014 13:57:29 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Saravana Kannan <skannan@...eaurora.org>,
	linux-kernel@...r.kernel.org,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Lenny Szubowicz <lszubowi@...hat.com>, linux-pm@...r.kernel.org
Subject: Re: [PATCH] cpufreq, store_scaling_governor requires policy->rwsem
 to be held for duration of changing governors [v2]



On 07/31/2014 12:36 PM, Rafael J. Wysocki wrote:
> On Thursday, July 31, 2014 06:23:18 AM Prarit Bhargava wrote:
>>
>> On 07/30/2014 10:16 PM, Rafael J. Wysocki wrote:
>>> On Wednesday, July 30, 2014 06:36:00 PM Saravana Kannan wrote:
>>>> On 07/30/2014 02:40 PM, Rafael J. Wysocki wrote:
>>>>> On Wednesday, July 30, 2014 10:18:25 AM Prarit Bhargava wrote:
>>>>>>
>>>>>> On 07/29/2014 08:03 PM, Rafael J. Wysocki wrote:
>>>>>>> On Tuesday, July 29, 2014 07:46:02 AM Prarit Bhargava wrote:
>>>>>
>>>>> [cut]
>>>>>
>>>>>>>> This patch effectively reverts commit 955ef483.
>>>>
>>>> The issue reported in this patch is valid. We are seeing that internally 
>>>> too. I believe I reported it in another thread (within the past month).
>>>>
>>>> However, the original patch fixes a real deadlock issue (I'm too tired 
>>>> to look it up now). We can revet the original, but it's going to bring 
>>>> back the original issue. I just want to make sure Prarit and Raphael 
>>>> realize this before proceeding.
>>>>
>>>> I do have plans for a proper fix for the mainline (not stable branches), 
>>>> but plan to do that after the current set of suspend/hotplug patches go 
>>>> through. The fix would be easier to make after that.
>>>>
>>>>>>>
>>>>>>> OK, I'm convinced by this.
>>>>>>>
>>>>>>> I suppose we should push it for -stable from 3.10 through 3.15.x, right?
>>>>>>
>>>>>> Rafael, I think that is a good idea.  I'm not sure what the protocol is for
>>>>>> adding stable@...nel.org though ...
>>
>> Rafael, let me (again) re-write the patch description.  I think Saravana has
>> raised an important issue that I have not clearly identified why it is safe to
>> remove this code in my patch description.  Also, I want to clearly identify the
>> appropriate -stable releases to push this out to.
>>
>> I'll submit a [v3] later today or tomorrow.
> 
> In any case that's too late for 3.16 final, unless there's an -rc8.
> 
> Thanks for doing that work!

Ugh ... I tried this (yet another) large system and hit another panic :(.

I'm investigating now, and I'm hoping this is just something "new".

P.

> 
> Rafael
> 
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