linux-kernel - Re: [PATCH V3 1/6] cpufreq: suspend governors on system suspend/hibernate

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Message-ID: <CAKohpok0E=m=63KXM22usiW7Rsu59cD7Q=+k3tRcW=8269tZnQ@mail.gmail.com>
Date:	Tue, 26 Nov 2013 07:56:19 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
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>,
	Nishanth Menon <nm@...com>,
	Stephen Warren <swarren@...dotorg.org>,
	Kgene Kim <kgene.kim@...sung.com>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	linux-tegra@...r.kernel.org, jinchoi@...adcom.com,
	Lan Tianyu <tianyu.lan@...el.com>,
	Sebastian Capella <sebastian.capella@...aro.org>,
	Jonghwan Choi <jhbird.choi@...sung.com>
Subject: Re: [PATCH V3 1/6] cpufreq: suspend governors on system suspend/hibernate

On 26 November 2013 04:59, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>> @@ -1259,6 +1262,8 @@ int dpm_suspend(pm_message_t state)
>>
>>       might_sleep();
>>
>> +     cpufreq_suspend();
>> +
>>
>>       mutex_lock(&dpm_list_mtx);
>>       pm_transition = state;
>>       async_error = 0;
>
> Shouldn't it do cpufreq_resume() on errors?

Yes and this is already done I believe. In case dpm_suspend() fails,
dpm_resume() gets called. Isn't it?

>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> +void cpufreq_suspend(void)
>> +{
>> +     struct cpufreq_policy *policy;
>> +
>> +     if (!has_target())
>> +             return;
>> +
>> +     pr_debug("%s: Suspending Governors\n", __func__);
>> +
>> +     list_for_each_entry(policy, &cpufreq_policy_list, policy_list)
>> +             if (__cpufreq_governor(policy, CPUFREQ_GOV_STOP))
>> +                     pr_err("%s: Failed to stop governor for policy: %p\n",
>> +                                     __func__, policy);
>
> This appears to be racy.  Is it really racy, or just seemingly?

Why does it look racy to you? Userspace should be frozen by now,
policy_list should be stable as well as nobody would touch it.
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