Re: [PATCH 3/3] cpufreq: Always update current frequency before startig governor

From	Viresh Kumar <viresh.kumar@linaro.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 3/3] cpufreq: Always update current frequency before startig governor
Date	2016-03-22 15:50 +0100
Message-ID	<rfvN7-5Sf-15@gated-at.bofh.it> (permalink)
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On 22-03-16, 15:33, Rafael J. Wysocki wrote:
> On Tuesday, March 22, 2016 09:00:32 AM Viresh Kumar wrote:

> > Why we did the same in process context earlier? And why it wouldn't be
> > a problem now, when we do it in interrupt context? Will IRQs be
> > disabled here? If so, then will you hit following ?
> 
> I'm not sure I'm following.

Sorry about that.

> This is process context too.
> 
> Look at the call sites of cpufreq_start_governor() (patch [1/3]):
> - cpufreq_offline() - process context
> - cpufreq_resume() - process context

I somehow thought that this is going to happen in interrupt context. :(

> - cpufreq_set_policy() - process context
> - cpufreq_add_policy_cpu() - process context
> 
> Besides, calling cpufreq_governor() from interrupt context wouldn't reall work,
> because that acquires mutexes etc, like in cpufreq_governor_init().
> 
> > static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
> > 		struct cpufreq_freqs *freqs, unsigned int state)
> > {
> > 	BUG_ON(irqs_disabled());
> > 
> > ...
> > }
> > 
> > And will calling notifiers from interrupt-context just fine ?
> 
> If your question is why the original code doesn't call cpufreq_update_policy()
> directly, I think the reason is because cpufreq_resume() used to be one of the
> syscore ops and *that* would have been run in interrupt context.

Yeah.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

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[PATCH 3/3] cpufreq: Always update current frequency before startig governor "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-03-21 15:50 +0100
  Re: [PATCH 3/3] cpufreq: Always update current frequency before  startig governor Viresh Kumar <viresh.kumar@linaro.org> - 2016-03-22 04:40 +0100
    Re: [PATCH 3/3] cpufreq: Always update current frequency before startig governor "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-03-22 15:40 +0100
      Re: [PATCH 3/3] cpufreq: Always update current frequency before  startig governor Viresh Kumar <viresh.kumar@linaro.org> - 2016-03-22 15:50 +0100

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