Re: [RFC v3] cpufreq: Make sure frequency transitions are serialized
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: 2014-03-20 08:37:51
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On 20 March 2014 14:02, Srivatsa S. Bhat [off-list ref] wrote:
quoted hunk ↗ jump to hunk
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 199b52b..5283f10 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c@@ -349,6 +349,39 @@ void cpufreq_notify_post_transition(struct cpufreq_policy *policy, EXPORT_SYMBOL_GPL(cpufreq_notify_post_transition); +void cpufreq_freq_transition_begin(struct cpufreq_policy *policy, + struct cpufreq_freqs *freqs, unsigned int state) +{ +wait: + wait_event(&policy->transition_wait, !policy->transition_ongoing); + + mutex_lock(&policy->transition_lock); + + if (policy->transition_ongoing) { + mutex_unlock(&policy->transition_lock); + goto wait; + } + + policy->transition_ongoing = true; + + mutex_unlock(&policy->transition_lock); + + cpufreq_notify_transition(policy, freqs, CPUFREQ_PRECHANGE); +} + +void cpufreq_freq_transition_end(struct cpufreq_policy *policy, + struct cpufreq_freqs *freqs, unsigned int state) +{ + cpufreq_notify_transition(policy, freqs, CPUFREQ_POSTCHANGE); + + mutex_lock(&policy->transition_lock);
Why do we need locking here? You explained that earlier :)
Also, I would like to add this here:
WARN_ON(policy->transition_ongoing);
+ policy->transition_ongoing = false; + mutex_unlock(&policy->transition_lock); + + wake_up(&policy->transition_wait); +}