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authorViresh Kumar <viresh.kumar@linaro.org>2013-06-19 10:16:55 +0530
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-06-27 21:49:55 +0200
commit7c30ed532cf798a8d924562f2f44d03d7652f7a7 (patch)
tree6198099d8f7fc69c3510908d539df878857684cd /drivers/cpufreq
parente11158c0c9ab59d46bb70953f6275643a7a01fa1 (diff)
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>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r--drivers/cpufreq/cpufreq.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index d976e222f10f..03b3b69f64a7 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -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)