cpufreq: Convert the cpufreq_driver_lock to a rwlock

This eliminates the contention I am seeing in __cpufreq_cpu_get.
It also nicely stages the lock to be replaced by the rcu.

Signed-off-by: Nathan Zimmer <nzimmer@sgi.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 26 insertions, 26 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index b02824d092e7..c5996fe7250e 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -45,7 +45,7 @@ static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
 /* This one keeps track of the previously set governor of a removed CPU */
 static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);
 #endif
-static DEFINE_SPINLOCK(cpufreq_driver_lock);
+static DEFINE_RWLOCK(cpufreq_driver_lock);
 
 /*
  * cpu_policy_rwsem is a per CPU reader-writer semaphore designed to cure
@@ -137,7 +137,7 @@ static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs)
                 goto err_out;
 
         /* get the cpufreq driver */
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        read_lock_irqsave(&cpufreq_driver_lock, flags);
 
         if (!cpufreq_driver)
                 goto err_out_unlock;
@@ -155,13 +155,13 @@ static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs)
         if (!sysfs && !kobject_get(&data->kobj))
                 goto err_out_put_module;
 
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        read_unlock_irqrestore(&cpufreq_driver_lock, flags);
         return data;
 
 err_out_put_module:
         module_put(cpufreq_driver->owner);
 err_out_unlock:
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        read_unlock_irqrestore(&cpufreq_driver_lock, flags);
 err_out:
         return NULL;
 }
@@ -266,9 +266,9 @@ void cpufreq_notify_transition(struct cpufreq_freqs *freqs, unsigned int state)
         pr_debug("notification %u of frequency transition to %u kHz\n",
                 state, freqs->new);
 
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        read_lock_irqsave(&cpufreq_driver_lock, flags);
         policy = per_cpu(cpufreq_cpu_data, freqs->cpu);
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        read_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
         switch (state) {
 
@@ -765,12 +765,12 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
                         goto err_out_kobj_put;
         }
 
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        write_lock_irqsave(&cpufreq_driver_lock, flags);
         for_each_cpu(j, policy->cpus) {
                 per_cpu(cpufreq_cpu_data, j) = policy;
                 per_cpu(cpufreq_policy_cpu, j) = policy->cpu;
         }
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
         ret = cpufreq_add_dev_symlink(cpu, policy);
         if (ret)
@@ -813,12 +813,12 @@ static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
 
         lock_policy_rwsem_write(sibling);
 
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        write_lock_irqsave(&cpufreq_driver_lock, flags);
 
         cpumask_set_cpu(cpu, policy->cpus);
         per_cpu(cpufreq_policy_cpu, cpu) = policy->cpu;
         per_cpu(cpufreq_cpu_data, cpu) = policy;
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
         unlock_policy_rwsem_write(sibling);
 
@@ -871,15 +871,15 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
 
 #ifdef CONFIG_HOTPLUG_CPU
         /* Check if this cpu was hot-unplugged earlier and has siblings */
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        read_lock_irqsave(&cpufreq_driver_lock, flags);
         for_each_online_cpu(sibling) {
                 struct cpufreq_policy *cp = per_cpu(cpufreq_cpu_data, sibling);
                 if (cp && cpumask_test_cpu(cpu, cp->related_cpus)) {
-                        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+                        read_unlock_irqrestore(&cpufreq_driver_lock, flags);
                         return cpufreq_add_policy_cpu(cpu, sibling, dev);
                 }
         }
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        read_unlock_irqrestore(&cpufreq_driver_lock, flags);
 #endif
 #endif
 
@@ -952,10 +952,10 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
         return 0;
 
 err_out_unregister:
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        write_lock_irqsave(&cpufreq_driver_lock, flags);
         for_each_cpu(j, policy->cpus)
                 per_cpu(cpufreq_cpu_data, j) = NULL;
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
         kobject_put(&policy->kobj);
         wait_for_completion(&policy->kobj_unregister);
@@ -1008,12 +1008,12 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
 
         pr_debug("%s: unregistering CPU %u\n", __func__, cpu);
 
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        write_lock_irqsave(&cpufreq_driver_lock, flags);
 
         data = per_cpu(cpufreq_cpu_data, cpu);
         per_cpu(cpufreq_cpu_data, cpu) = NULL;
 
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
         if (!data) {
                 pr_debug("%s: No cpu_data found\n", __func__);
@@ -1047,9 +1047,9 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
                         WARN_ON(lock_policy_rwsem_write(cpu));
                         cpumask_set_cpu(cpu, data->cpus);
 
-                        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+                        write_lock_irqsave(&cpufreq_driver_lock, flags);
                         per_cpu(cpufreq_cpu_data, cpu) = data;
-                        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+                        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
                         unlock_policy_rwsem_write(cpu);
 
@@ -1848,13 +1848,13 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
         if (driver_data->setpolicy)
                 driver_data->flags |= CPUFREQ_CONST_LOOPS;
 
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        write_lock_irqsave(&cpufreq_driver_lock, flags);
         if (cpufreq_driver) {
-                spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+                write_unlock_irqrestore(&cpufreq_driver_lock, flags);
                 return -EBUSY;
         }
         cpufreq_driver = driver_data;
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
         ret = subsys_interface_register(&cpufreq_interface);
         if (ret)
@@ -1886,9 +1886,9 @@ int cpufreq_register_driver(struct cpufreq_driver *driver_data)
 err_if_unreg:
         subsys_interface_unregister(&cpufreq_interface);
 err_null_driver:
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        write_lock_irqsave(&cpufreq_driver_lock, flags);
         cpufreq_driver = NULL;
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
         return ret;
 }
 EXPORT_SYMBOL_GPL(cpufreq_register_driver);
@@ -1914,9 +1914,9 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver)
         subsys_interface_unregister(&cpufreq_interface);
         unregister_hotcpu_notifier(&cpufreq_cpu_notifier);
 
-        spin_lock_irqsave(&cpufreq_driver_lock, flags);
+        write_lock_irqsave(&cpufreq_driver_lock, flags);
         cpufreq_driver = NULL;
-        spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
+        write_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
         return 0;
 }