linux-kernel - Re: [PATCH V2 07/11] cpufreq: Use cpufreq_policy

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Date:	Tue, 20 Aug 2013 12:05:39 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	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>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Subject: Re: [PATCH V2 07/11] cpufreq: Use cpufreq_policy_list for iterating
 over policies

On 19 August 2013 16:57, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> It wasn't my patch actually.. It only made it visible that's it :)
> The problem is:
> - On suspend all CPUs are removed and so governors are
> stopped.
> - On resume, handle_update() is called for the boot cpu and
> cpu_add_dev for all others.
>
> handle_update() doesn't start governor but only plays with
> CPUFREQ_GOV_LIMITS.. when we start adding other
> CPUs and call: cpufreq_add_policy_cpu() which fails in
> following call:
>
> __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
>
> and so cpufreq_policy_cpu never gets initialized to
> policy->cpu and stays at -1, and hence the crash.
>
> So, there are few problems with core at this point:
> - I don't understand how does the work done in
> cpufreq_add_dev() gets done for boot cpu during
> resume ? And so how does Srivatsa's "frozen" solution
> really works (I haven't had time to investigate, its not
> that I couldn't understand it :) )..
>
> - We need to start governor boot cpu in handle_update()
> and things would be solved...

Whatever I wrote here was simply _Bullshit_ :(

I am about to send you a fixup patchset that fixes this issue, and
yes it was my patch which introduced this problem :(, but
because of some mishandling of cpufreq_policy_list :)

--
viresh
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