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

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Date:	Thu, 31 Jul 2014 18:36:47 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Prarit Bhargava <prarit@...hat.com>
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 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!

Rafael

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