Commit 7c30ed53 authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki
Browse files

cpufreq: make sure frequency transitions are serialized 



Whenever we are changing frequency of a cpu, we are calling PRECHANGE and
POSTCHANGE notifiers. They must be serialized. i.e. PRECHANGE or POSTCHANGE
shouldn't be called twice contiguously.

This can happen due to bugs in users of __cpufreq_driver_target() or actual
cpufreq drivers who are sending these notifiers.

This patch adds some protection against this. Now, we keep track of the last
transaction and see if something went wrong.

Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent e11158c0

drivers/cpufreq/cpufreq.c

+14 −0
Original line number Diff line number Diff line
@@ -312,6 +312,12 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy, 
	switch (state) {



	case CPUFREQ_PRECHANGE:

		if (WARN(policy->transition_ongoing,

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

			return;



		policy->transition_ongoing = true;



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

		 * which is not equal to what the cpufreq core thinks is

		 * "old frequency".
@@ -331,6 +337,12 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy, 
		break;



	case CPUFREQ_POSTCHANGE:

		if (WARN(!policy->transition_ongoing,

				"No frequency transition in progress\n"))

			return;



		policy->transition_ongoing = false;



		adjust_jiffies(CPUFREQ_POSTCHANGE, freqs);

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

			(unsigned long)freqs->cpu);
@@ -1539,6 +1551,8 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, 


	if (cpufreq_disabled())

		return -ENODEV;

	if (policy->transition_ongoing)

		return -EBUSY;



	/* Make sure that target_freq is within supported range */

	if (target_freq > policy->max)

include/linux/cpufreq.h

+1 −0
Original line number Diff line number Diff line
@@ -119,6 +119,7 @@ struct cpufreq_policy { 


	struct kobject		kobj;

	struct completion	kobj_unregister;

	bool			transition_ongoing; /* Tracks transition status */

};



#define CPUFREQ_ADJUST			(0)

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