[PATCH v2] cpufreq: unlock when failing cpufreq_update_policy()

[Aaron Plattner <aplattner@nvidia.com>]

Commit bd0fa9bb455d introduced a failure path to cpufreq_update_policy() if
cpufreq_driver->get(cpu) returns NULL.  However, it jumps to the 'no_policy'
label, which exits without unlocking any of the locks the function acquired
earlier.  This causes later calls into cpufreq to hang.

Fix this by creating a new 'unlock' label and jumping to that instead.

v2: Delete the no_policy label and just return early if policy is NULL.

Fixes: bd0fa9bb455d ("cpufreq: Return error if ->get() failed in cpufreq_update_policy()")
Link: https://devtalk.nvidia.com/default/topic/751903/kernel-3-15-and-nv-drivers-337-340-failed-to-initialize-the-nvidia-kernel-module-gtx-550-ti-/
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
---
v1 of this was tested by the user affected by the problem, but I don't have his
email address so I can't add it as a Tested-by line.

 drivers/cpufreq/cpufreq.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index aed2b0cb83dc..62259d27f03e 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2242,10 +2242,8 @@ int cpufreq_update_policy(unsigned int cpu)
 	struct cpufreq_policy new_policy;
 	int ret;
 
-	if (!policy) {
-		ret = -ENODEV;
-		goto no_policy;
-	}
+	if (!policy)
+		return -ENODEV;
 
 	down_write(&policy->rwsem);
 
@@ -2264,7 +2262,7 @@ int cpufreq_update_policy(unsigned int cpu)
 		new_policy.cur = cpufreq_driver->get(cpu);
 		if (WARN_ON(!new_policy.cur)) {
 			ret = -EIO;
-			goto no_policy;
+			goto unlock;
 		}
 
 		if (!policy->cur) {
@@ -2279,10 +2277,10 @@ int cpufreq_update_policy(unsigned int cpu)
 
 	ret = cpufreq_set_policy(policy, &new_policy);
 
+unlock:
 	up_write(&policy->rwsem);
 
 	cpufreq_cpu_put(policy);
-no_policy:
 	return ret;
 }
 EXPORT_SYMBOL(cpufreq_update_policy);
-- 
2.0.0