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Commit 0d1857a1 authored by Nathan Zimmer's avatar Nathan Zimmer Committed by Rafael J. Wysocki
Browse files

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: default avatarNathan Zimmer <nzimmer@sgi.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 07961ac7

drivers/cpufreq/cpufreq.c

+26 −26
Original line number Diff line number Diff line
@@ -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;

}