[PATCH v1 04/10] cpufreq: Add and use cpufreq policy locking guards

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Introduce "read" and "write" locking guards for cpufreq policies and use
them where applicable in the cpufreq core.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/cpufreq/cpufreq.c |  121 ++++++++++++++++++++--------------------------
 include/linux/cpufreq.h   |    6 ++
 2 files changed, 60 insertions(+), 67 deletions(-)

--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -987,17 +987,16 @@
 {
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
-	ssize_t ret = -EBUSY;
 
 	if (!fattr->show)
 		return -EIO;
 
-	down_read(&policy->rwsem);
+	guard(cpufreq_policy_read)(policy);
+
 	if (likely(!policy_is_inactive(policy)))
-		ret = fattr->show(policy, buf);
-	up_read(&policy->rwsem);
+		return fattr->show(policy, buf);
 
-	return ret;
+	return -EBUSY;
 }
 
 static ssize_t store(struct kobject *kobj, struct attribute *attr,
@@ -1005,17 +1004,16 @@
 {
 	struct cpufreq_policy *policy = to_policy(kobj);
 	struct freq_attr *fattr = to_attr(attr);
-	ssize_t ret = -EBUSY;
 
 	if (!fattr->store)
 		return -EIO;
 
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
+
 	if (likely(!policy_is_inactive(policy)))
-		ret = fattr->store(policy, buf, count);
-	up_write(&policy->rwsem);
+		return fattr->store(policy, buf, count);
 
-	return ret;
+	return -EBUSY;
 }
 
 static void cpufreq_sysfs_release(struct kobject *kobj)
@@ -1167,7 +1165,8 @@
 	if (cpumask_test_cpu(cpu, policy->cpus))
 		return 0;
 
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
+
 	if (has_target())
 		cpufreq_stop_governor(policy);
 
@@ -1178,7 +1177,7 @@
 		if (ret)
 			pr_err("%s: Failed to start governor\n", __func__);
 	}
-	up_write(&policy->rwsem);
+
 	return ret;
 }
 
@@ -1198,9 +1197,10 @@
 		container_of(work, struct cpufreq_policy, update);
 
 	pr_debug("handle_update for cpu %u called\n", policy->cpu);
-	down_write(&policy->rwsem);
+
+	guard(cpufreq_policy_write)(policy);
+
 	refresh_frequency_limits(policy);
-	up_write(&policy->rwsem);
 }
 
 static int cpufreq_notifier_min(struct notifier_block *nb, unsigned long freq,
@@ -1226,11 +1226,11 @@
 	struct kobject *kobj;
 	struct completion *cmp;
 
-	down_write(&policy->rwsem);
-	cpufreq_stats_free_table(policy);
-	kobj = &policy->kobj;
-	cmp = &policy->kobj_unregister;
-	up_write(&policy->rwsem);
+	scoped_guard(cpufreq_policy_write, policy) {
+		cpufreq_stats_free_table(policy);
+		kobj = &policy->kobj;
+		cmp = &policy->kobj_unregister;
+	}
 	kobject_put(kobj);
 
 	/*
@@ -1381,7 +1381,7 @@
 	unsigned int j;
 	int ret;
 
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
 
 	policy->cpu = cpu;
 	policy->governor = NULL;
@@ -1558,10 +1558,7 @@
 		goto out_destroy_policy;
 	}
 
-out_unlock:
-	up_write(&policy->rwsem);
-
-	return ret;
+	return 0;
 
 out_destroy_policy:
 	for_each_cpu(j, policy->real_cpus)
@@ -1578,7 +1575,7 @@
 out_clear_policy:
 	cpumask_clear(policy->cpus);
 
-	goto out_unlock;
+	return ret;
 }
 
 static int cpufreq_online(unsigned int cpu)
@@ -1726,11 +1723,10 @@
 		return 0;
 	}
 
-	down_write(&policy->rwsem);
+	guard(cpufreq_policy_write)(policy);
 
 	__cpufreq_offline(cpu, policy);
 
-	up_write(&policy->rwsem);
 	return 0;
 }
 
@@ -1747,33 +1743,29 @@
 	if (!policy)
 		return;
 
-	down_write(&policy->rwsem);
+	scoped_guard(cpufreq_policy_write, policy) {
+		if (cpu_online(cpu))
+			__cpufreq_offline(cpu, policy);
 
-	if (cpu_online(cpu))
-		__cpufreq_offline(cpu, policy);
+		remove_cpu_dev_symlink(policy, cpu, dev);
 
-	remove_cpu_dev_symlink(policy, cpu, dev);
+		if (!cpumask_empty(policy->real_cpus))
+			return;
 
-	if (!cpumask_empty(policy->real_cpus)) {
-		up_write(&policy->rwsem);
-		return;
-	}
+		/*
+		 * Unregister cpufreq cooling once all the CPUs of the policy
+		 * are removed.
+		 */
+		if (cpufreq_thermal_control_enabled(cpufreq_driver)) {
+			cpufreq_cooling_unregister(policy->cdev);
+			policy->cdev = NULL;
+		}
 
-	/*
-	 * Unregister cpufreq cooling once all the CPUs of the policy are
-	 * removed.
-	 */
-	if (cpufreq_thermal_control_enabled(cpufreq_driver)) {
-		cpufreq_cooling_unregister(policy->cdev);
-		policy->cdev = NULL;
+		/* We did light-weight exit earlier, do full tear down now */
+		if (cpufreq_driver->offline && cpufreq_driver->exit)
+			cpufreq_driver->exit(policy);
 	}
 
-	/* We did light-weight exit earlier, do full tear down now */
-	if (cpufreq_driver->offline && cpufreq_driver->exit)
-		cpufreq_driver->exit(policy);
-
-	up_write(&policy->rwsem);
-
 	cpufreq_policy_free(policy);
 }
 
@@ -1926,15 +1918,16 @@
 	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
 	unsigned int ret_freq = 0;
 
-	if (policy) {
-		down_read(&policy->rwsem);
+	if (!policy)
+		return 0;
+
+	scoped_guard(cpufreq_policy_read, policy) {
 		if (cpufreq_driver->get)
 			ret_freq = __cpufreq_get(policy);
-		up_read(&policy->rwsem);
-
-		cpufreq_cpu_put(policy);
 	}
 
+	cpufreq_cpu_put(policy);
+
 	return ret_freq;
 }
 EXPORT_SYMBOL(cpufreq_get);
@@ -1994,9 +1987,9 @@
 
 	for_each_active_policy(policy) {
 		if (has_target()) {
-			down_write(&policy->rwsem);
-			cpufreq_stop_governor(policy);
-			up_write(&policy->rwsem);
+			scoped_guard(cpufreq_policy_write, policy) {
+				cpufreq_stop_governor(policy);
+			}
 		}
 
 		if (cpufreq_driver->suspend && cpufreq_driver->suspend(policy))
@@ -2037,9 +2030,9 @@
 			pr_err("%s: Failed to resume driver: %s\n", __func__,
 				cpufreq_driver->name);
 		} else if (has_target()) {
-			down_write(&policy->rwsem);
-			ret = cpufreq_start_governor(policy);
-			up_write(&policy->rwsem);
+			scoped_guard(cpufreq_policy_write, policy) {
+				ret = cpufreq_start_governor(policy);
+			}
 
 			if (ret)
 				pr_err("%s: Failed to start governor for CPU%u's policy\n",
@@ -2406,15 +2399,9 @@
 			  unsigned int target_freq,
 			  unsigned int relation)
 {
-	int ret;
+	guard(cpufreq_policy_write)(policy);
 
-	down_write(&policy->rwsem);
-
-	ret = __cpufreq_driver_target(policy, target_freq, relation);
-
-	up_write(&policy->rwsem);
-
-	return ret;
+	return __cpufreq_driver_target(policy, target_freq, relation);
 }
 EXPORT_SYMBOL_GPL(cpufreq_driver_target);
 
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -170,6 +170,12 @@
 	struct notifier_block nb_max;
 };
 
+DEFINE_GUARD(cpufreq_policy_write, struct cpufreq_policy *,
+	     down_write(&_T->rwsem), up_write(&_T->rwsem))
+
+DEFINE_GUARD(cpufreq_policy_read, struct cpufreq_policy *,
+	     down_read(&_T->rwsem), up_read(&_T->rwsem))
+
 /*
  * Used for passing new cpufreq policy data to the cpufreq driver's ->verify()
  * callback for sanitization.  That callback is only expected to modify the min