cpufreq: improve error checking on return values of __cpufreq_governor()

The __cpufreq_governor() function can fail in rare cases especially
if there are bugs in cpufreq drivers.  Thus we must stop processing
as soon as this routine fails, otherwise it may result in undefined
behavior.

This patch adds error checking code whenever this routine is called
from any place.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq.c

@@ -874,8 +874,13 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy,
 	int ret = 0, has_target = !!cpufreq_driver->target;
 	unsigned long flags;
 
-	if (has_target)
-		__cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+	if (has_target) {
+		ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+		if (ret) {
+			pr_err("%s: Failed to stop governor\n", __func__);
+			return ret;
+		}
+	}
 
 	lock_policy_rwsem_write(policy->cpu);
 
@@ -889,8 +894,11 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy,
 	unlock_policy_rwsem_write(policy->cpu);
 
 	if (has_target) {
-		__cpufreq_governor(policy, CPUFREQ_GOV_START);
-		__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+		if ((ret = __cpufreq_governor(policy, CPUFREQ_GOV_START)) ||
+			(ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))) {
+			pr_err("%s: Failed to start governor\n", __func__);
+			return ret;
+		}
 	}
 
 	/* Don't touch sysfs links during light-weight init */
@@ -1172,7 +1180,7 @@ static int __cpufreq_remove_dev(struct device *dev,
 				struct subsys_interface *sif, bool frozen)
 {
 	unsigned int cpu = dev->id, cpus;
-	int new_cpu;
+	int new_cpu, ret;
 	unsigned long flags;
 	struct cpufreq_policy *policy;
 	struct kobject *kobj;
@@ -1196,8 +1204,13 @@ static int __cpufreq_remove_dev(struct device *dev,
 		return -EINVAL;
 	}
 
-	if (cpufreq_driver->target)
-		__cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+	if (cpufreq_driver->target) {
+		ret = __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
+		if (ret) {
+			pr_err("%s: Failed to stop governor\n", __func__);
+			return ret;
+		}
+	}
 
 #ifdef CONFIG_HOTPLUG_CPU
 	if (!cpufreq_driver->setpolicy)
@@ -1231,8 +1244,15 @@ static int __cpufreq_remove_dev(struct device *dev,
 
 	/* If cpu is last user of policy, free policy */
 	if (cpus == 1) {
-		if (cpufreq_driver->target)
-			__cpufreq_governor(policy, CPUFREQ_GOV_POLICY_EXIT);
+		if (cpufreq_driver->target) {
+			ret = __cpufreq_governor(policy,
+					CPUFREQ_GOV_POLICY_EXIT);
+			if (ret) {
+				pr_err("%s: Failed to exit governor\n",
+						__func__);
+				return ret;
+			}
+	}
 
 		if (!frozen) {
 			lock_policy_rwsem_read(cpu);
@@ -1263,8 +1283,12 @@ static int __cpufreq_remove_dev(struct device *dev,
 			cpufreq_policy_free(policy);
 	} else {
 		if (cpufreq_driver->target) {
-			__cpufreq_governor(policy, CPUFREQ_GOV_START);
-			__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+			if ((ret = __cpufreq_governor(policy, CPUFREQ_GOV_START)) ||
+					(ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS))) {
+				pr_err("%s: Failed to start governor\n",
+						__func__);
+				return ret;
+			}
 		}
 	}
 
@@ -1912,7 +1936,7 @@ static int __cpufreq_set_policy(struct cpufreq_policy *policy,
 			/* might be a policy change, too, so fall through */
 		}
 		pr_debug("governor: change or update limits\n");
-		__cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
+		ret = __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
 	}
 
 error_out: