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: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index d976e22..03b3b69 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -312,6 +312,12 @@
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 @@
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 @@
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)
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 3c7ee2f..c0bc737 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -119,6 +119,7 @@
struct kobject kobj;
struct completion kobj_unregister;
+ bool transition_ongoing; /* Tracks transition status */
};
#define CPUFREQ_ADJUST (0)