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Commit 266c13d7 authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki
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cpufreq: Fix serialization of frequency transitions 



Commit 7c30ed ("cpufreq: make sure frequency transitions are serialized")
interacts poorly with systems that have a single core freqency for all
cores.  On such systems we have a single policy for all cores with
several CPUs.  When we do a frequency transition the governor calls the
pre and post change notifiers which causes cpufreq_notify_transition()
per CPU.  Since the policy is the same for all of them all CPUs after
the first and the warnings added are generated by checking a per-policy
flag the warnings will be triggered for all cores after the first.

Fix this by allowing notifier to be called for n times. Where n is the number of
cpus in policy->cpus.

Reported-and-tested-by: default avatarMark Brown <broonie@linaro.org>
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent f991fae5

drivers/cpufreq/cpufreq.c

+4 −3
Original line number Diff line number Diff line
@@ -312,11 +312,12 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy, 
	switch (state) {



	case CPUFREQ_PRECHANGE:

		if (WARN(policy->transition_ongoing,

		if (WARN(policy->transition_ongoing ==

					cpumask_weight(policy->cpus),

				"In middle of another frequency transition\n"))

			return;



		policy->transition_ongoing = true;

		policy->transition_ongoing++;



		/* detect if the driver reported a value as "old frequency"

		 * which is not equal to what the cpufreq core thinks is
@@ -341,7 +342,7 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy, 
				"No frequency transition in progress\n"))

			return;



		policy->transition_ongoing = false;

		policy->transition_ongoing--;



		adjust_jiffies(CPUFREQ_POSTCHANGE, freqs);

		pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new,

include/linux/cpufreq.h

+1 −1
Original line number Diff line number Diff line
@@ -119,7 +119,7 @@ struct cpufreq_policy { 


	struct kobject		kobj;

	struct completion	kobj_unregister;

	bool			transition_ongoing; /* Tracks transition status */

	int			transition_ongoing; /* Tracks transition status */

};



#define CPUFREQ_ADJUST			(0)