linux-kernel - Re: [PATCH 2/2] cpufreq: serialize calls to __cpufreq

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Message-ID: <CAKohpom-UFkvORuuzAEUj1jVofHTEkDMhSmMUo4_0Xxfj605-g@mail.gmail.com>
Date:	Tue, 10 Sep 2013 12:22:12 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Patch Tracking <patches@...aro.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] cpufreq: serialize calls to __cpufreq_governor()

Back finally and I see lots of mails over cpufreq stuff.. :)

On 3 September 2013 18:50, Srivatsa S. Bhat
<srivatsa.bhat@...ux.vnet.ibm.com> wrote:
> This doesn't solve the problem completely: it prevents the store_*() task
> from continuing *only* when it concurrently executes the __cpufreq_governor()
> function along with the CPU offline task. But if the two calls don't overlap,
> we will still have the possibility where the store_*() task tries to acquire
> the timer mutex after the CPU offline task has just finished destroying it.

How exactly? My brain is still on vacations :)

Anyway, this was one of the problem that I tried to solve with my patch.
But there can be other race conditions where things can go wrong and so
that patch may still be useful.

Call to __cpufreq_governor() must be serialized I believe.
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