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cpufreq: make sure frequency transitions are serialized

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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: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Viresh Kumar 2013-06-19 10:16:55 +05:30 • committed by Rafael J. Wysocki
parent e11158c0c9
commit 7c30ed532c
2 changed files with 15 additions and 0 deletions
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14
drivers/cpufreq/cpufreq.c
View file

@ -312,6 +312,12 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
switch (state) { switch (state) {
case CPUFREQ_PRECHANGE: 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" /* detect if the driver reported a value as "old frequency"
* which is not equal to what the cpufreq core thinks is * which is not equal to what the cpufreq core thinks is
* "old frequency". * "old frequency".
@ -331,6 +337,12 @@ static void __cpufreq_notify_transition(struct cpufreq_policy *policy,
break; break;
case CPUFREQ_POSTCHANGE: case CPUFREQ_POSTCHANGE:
if (WARN(!policy->transition_ongoing,
"No frequency transition in progress\n"))
return;
policy->transition_ongoing = false;
adjust_jiffies(CPUFREQ_POSTCHANGE, freqs); adjust_jiffies(CPUFREQ_POSTCHANGE, freqs);
pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new, pr_debug("FREQ: %lu - CPU: %lu", (unsigned long)freqs->new,
(unsigned long)freqs->cpu); (unsigned long)freqs->cpu);
@ -1539,6 +1551,8 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
if (cpufreq_disabled()) if (cpufreq_disabled())
return -ENODEV; return -ENODEV;
if (policy->transition_ongoing)
return -EBUSY;
/* Make sure that target_freq is within supported range */ /* Make sure that target_freq is within supported range */
if (target_freq > policy->max) if (target_freq > policy->max)

1
include/linux/cpufreq.h
View file

@ -119,6 +119,7 @@ struct cpufreq_policy {
struct kobject kobj; struct kobject kobj;
struct completion kobj_unregister; struct completion kobj_unregister;
bool transition_ongoing; /* Tracks transition status */
}; };
#define CPUFREQ_ADJUST (0) #define CPUFREQ_ADJUST (0)