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From: Andrej Gelenberg on 11 May 2010 10:30
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(a)udo.edu>
---
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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