Re: [PATCH v4 6/7] cpufreq: Support for fast frequency switching

Peter Zijlstra
2016-03-16T15:38:08Z

On Wed, Mar 16, 2016 at 03:52:28PM +0100, Rafael J. Wysocki wrote:
> +/**
> + * cpufreq_enable_fast_switch - Enable fast frequency switching for policy.
> + * @policy: cpufreq policy to enable fast frequency switching for.
> + *
> + * Try to enable fast frequency switching for @policy.
> + *
> + * The attempt will fail if there is at least one transition notifier registered
> + * at this point, as fast frequency switching is quite fundamentally at odds
> + * with transition notifiers. Thus if successful, it will make registration of
> + * transition notifiers fail going forward.
> + *
> + * Call under policy->rwsem.

Nobody reads a comment..

> + */
> +void cpufreq_enable_fast_switch(struct cpufreq_policy *policy)
> +{

lockdep_assert_held(&policy->rwsem);

While everybody complains when there's a big nasty splat in their dmesg
;-)

> + mutex_lock(&cpufreq_fast_switch_lock);
> + if (policy->fast_switch_possible && cpufreq_fast_switch_count >= 0) {
> + cpufreq_fast_switch_count++;
> + policy->fast_switch_enabled = true;
> + } else {
> + pr_warn("cpufreq: CPU%u: Fast freqnency switching not enabled\n",
> + policy->cpu);
> + }
> + mutex_unlock(&cpufreq_fast_switch_lock);
> +}