[PATCH] [CPUFREQ] fix race condition in store_scaling_governor

[Andrej Gelenberg]

Wrap store_scaling_governor with mutex lock cpufreq_governor_mutex.
Fix kernel panic if switch scaling governor very fast.
Bug in bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=15948

Signed-off-by: Andrej Gelenberg <andrej.gelenberg@xxxxxxx>
---
 drivers/cpufreq/cpufreq.c |   16 +++++++++++-----
 1 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 75d293e..6ba42f9 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -403,8 +403,6 @@ static int cpufreq_parse_governor(char 
*str_governor, unsigned int *policy,
 	} else if (cpufreq_driver->target) {
 		struct cpufreq_governor *t;

-		mutex_lock(&cpufreq_governor_mutex);
-
 		t = __find_governor(str_governor);

 		if (t == NULL) {
@@ -429,8 +427,6 @@ static int cpufreq_parse_governor(char 
*str_governor, unsigned int *policy,
 			*governor = t;
 			err = 0;
 		}
-
-		mutex_unlock(&cpufreq_governor_mutex);
 	}
 out:
 	return err;
@@ -521,7 +517,7 @@ static ssize_t show_scaling_governor(struct 
cpufreq_policy *policy, char *buf)
 /**
  * store_scaling_governor - store policy for the specified CPU
  */
-static ssize_t store_scaling_governor(struct cpufreq_policy *policy,
+static ssize_t _store_scaling_governor(struct cpufreq_policy *policy,
 					const char *buf, size_t count)
 {
 	unsigned int ret = -EINVAL;
@@ -553,6 +549,16 @@ static ssize_t store_scaling_governor(struct 
cpufreq_policy *policy,
 		return count;
 }

+static ssize_t store_scaling_governor(struct cpufreq_policy *policy,
+                                        const char *buf, size_t count)
+{
+        ssize_t ret;
+	mutex_lock(&cpufreq_governor_mutex);
+        ret = _store_scaling_governor(policy, buf, count);
+	mutex_unlock(&cpufreq_governor_mutex);
+        return ret;
+}
+
 /**
  * show_scaling_driver - show the cpufreq driver currently loaded
  */
--
1.7.1

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