Commit 153d7f3f authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Linus Torvalds
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[PATCH] Reorganize the cpufreq cpu hotplug locking to not be totally bizare 



The patch below moves the cpu hotplugging higher up in the cpufreq
layering; this is needed to avoid recursive taking of the cpu hotplug
lock and to otherwise detangle the mess.

The new rules are:
1. you must do lock_cpu_hotplug() around the following functions:
   __cpufreq_driver_target
   __cpufreq_governor (for CPUFREQ_GOV_LIMITS operation only)
   __cpufreq_set_policy
2. governer methods (.governer) must NOT take the lock_cpu_hotplug()
   lock in any way; they are called with the lock taken already
3. if your governer spawns a thread that does things, like calling
   __cpufreq_driver_target, your thread must honor rule #1.
4. the policy lock and other cpufreq internal locks nest within
   the lock_cpu_hotplug() lock.

I'm not entirely happy about how the __cpufreq_governor rule ended up
(conditional locking rule depending on the argument) but basically all
callers pass this as a constant so it's not too horrible.

The patch also removes the cpufreq_governor() function since during the
locking audit it turned out to be entirely unused (so no need to fix it)

The patch works on my testbox, but it could use more testing
(otoh... it can't be much worse than the current code)

Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 44eb1231

drivers/cpufreq/cpufreq.c

+18 −22
Original line number Diff line number Diff line
@@ -364,10 +364,12 @@ static ssize_t store_##file_name \ 
	if (ret != 1)							\

		return -EINVAL;						\

									\

	lock_cpu_hotplug();						\

	mutex_lock(&policy->lock);					\

	ret = __cpufreq_set_policy(policy, &new_policy);		\

	policy->user_policy.object = policy->object;			\

	mutex_unlock(&policy->lock);					\

	unlock_cpu_hotplug();						\

									\

	return ret ? ret : count;					\

}
@@ -1197,20 +1199,18 @@ EXPORT_SYMBOL(cpufreq_unregister_notifier); 
 *********************************************************************/





/* Must be called with lock_cpu_hotplug held */

int __cpufreq_driver_target(struct cpufreq_policy *policy,

			    unsigned int target_freq,

			    unsigned int relation)

{

	int retval = -EINVAL;



	lock_cpu_hotplug();

	dprintk("target for CPU %u: %u kHz, relation %u\n", policy->cpu,

		target_freq, relation);

	if (cpu_online(policy->cpu) && cpufreq_driver->target)

		retval = cpufreq_driver->target(policy, target_freq, relation);



	unlock_cpu_hotplug();



	return retval;

}

EXPORT_SYMBOL_GPL(__cpufreq_driver_target);
@@ -1225,17 +1225,23 @@ int cpufreq_driver_target(struct cpufreq_policy *policy, 
	if (!policy)

		return -EINVAL;



	lock_cpu_hotplug();

	mutex_lock(&policy->lock);



	ret = __cpufreq_driver_target(policy, target_freq, relation);



	mutex_unlock(&policy->lock);

	unlock_cpu_hotplug();



	cpufreq_cpu_put(policy);

	return ret;

}

EXPORT_SYMBOL_GPL(cpufreq_driver_target);



/*

 * Locking: Must be called with the lock_cpu_hotplug() lock held

 * when "event" is CPUFREQ_GOV_LIMITS

 */



static int __cpufreq_governor(struct cpufreq_policy *policy, unsigned int event)

{
@@ -1257,24 +1263,6 @@ static int __cpufreq_governor(struct cpufreq_policy *policy, unsigned int event) 
}





int cpufreq_governor(unsigned int cpu, unsigned int event)

{

	int ret = 0;

	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);



	if (!policy)

		return -EINVAL;



	mutex_lock(&policy->lock);

	ret = __cpufreq_governor(policy, event);

	mutex_unlock(&policy->lock);



	cpufreq_cpu_put(policy);

	return ret;

}

EXPORT_SYMBOL_GPL(cpufreq_governor);





int cpufreq_register_governor(struct cpufreq_governor *governor)

{

	struct cpufreq_governor *t;
@@ -1342,6 +1330,9 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu) 
EXPORT_SYMBOL(cpufreq_get_policy);





/*

 * Locking: Must be called with the lock_cpu_hotplug() lock held

 */

static int __cpufreq_set_policy(struct cpufreq_policy *data, struct cpufreq_policy *policy)

{

	int ret = 0;
@@ -1436,6 +1427,8 @@ int cpufreq_set_policy(struct cpufreq_policy *policy) 
	if (!data)

		return -EINVAL;



	lock_cpu_hotplug();



	/* lock this CPU */

	mutex_lock(&data->lock);
@@ -1446,6 +1439,8 @@ int cpufreq_set_policy(struct cpufreq_policy *policy) 
	data->user_policy.governor = data->governor;



	mutex_unlock(&data->lock);



	unlock_cpu_hotplug();

	cpufreq_cpu_put(data);



	return ret;
@@ -1469,6 +1464,7 @@ int cpufreq_update_policy(unsigned int cpu) 
	if (!data)

		return -ENODEV;



	lock_cpu_hotplug();

	mutex_lock(&data->lock);



	dprintk("updating policy for CPU %u\n", cpu);
@@ -1494,7 +1490,7 @@ int cpufreq_update_policy(unsigned int cpu) 
	ret = __cpufreq_set_policy(data, &policy);



	mutex_unlock(&data->lock);



	unlock_cpu_hotplug();

	cpufreq_cpu_put(data);

	return ret;

}

drivers/cpufreq/cpufreq_conservative.c

+0 −2
Original line number Diff line number Diff line
@@ -525,7 +525,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 
		break;



	case CPUFREQ_GOV_LIMITS:

		lock_cpu_hotplug();

		mutex_lock(&dbs_mutex);

		if (policy->max < this_dbs_info->cur_policy->cur)

			__cpufreq_driver_target(
@@ -536,7 +535,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 
					this_dbs_info->cur_policy,

				       	policy->min, CPUFREQ_RELATION_L);

		mutex_unlock(&dbs_mutex);

		unlock_cpu_hotplug();

		break;

	}

	return 0;

drivers/cpufreq/cpufreq_ondemand.c

+2 −2
Original line number Diff line number Diff line
@@ -309,7 +309,9 @@ static void do_dbs_timer(void *data) 
	if (!dbs_info->enable)

		return;



	lock_cpu_hotplug();

	dbs_check_cpu(dbs_info);

	unlock_cpu_hotplug();

	queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work,

			usecs_to_jiffies(dbs_tuners_ins.sampling_rate));

}
@@ -412,7 +414,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 
		break;



	case CPUFREQ_GOV_LIMITS:

		lock_cpu_hotplug();

		mutex_lock(&dbs_mutex);

		if (policy->max < this_dbs_info->cur_policy->cur)

			__cpufreq_driver_target(this_dbs_info->cur_policy,
@@ -423,7 +424,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 
			                        policy->min,

			                        CPUFREQ_RELATION_L);

		mutex_unlock(&dbs_mutex);

		unlock_cpu_hotplug();

		break;

	}

	return 0;

drivers/cpufreq/cpufreq_userspace.c

+3 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <linux/spinlock.h>

#include <linux/interrupt.h>

#include <linux/cpufreq.h>

#include <linux/cpu.h>

#include <linux/types.h>

#include <linux/fs.h>

#include <linux/sysfs.h>
@@ -70,6 +71,7 @@ static int cpufreq_set(unsigned int freq, struct cpufreq_policy *policy) 


	dprintk("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);



	lock_cpu_hotplug();

	mutex_lock(&userspace_mutex);

	if (!cpu_is_managed[policy->cpu])

		goto err;
@@ -92,6 +94,7 @@ static int cpufreq_set(unsigned int freq, struct cpufreq_policy *policy) 


 err:

	mutex_unlock(&userspace_mutex);

	unlock_cpu_hotplug();

	return ret;

}

include/linux/cpufreq.h

+0 −3
Original line number Diff line number Diff line
@@ -172,9 +172,6 @@ extern int __cpufreq_driver_target(struct cpufreq_policy *policy, 
				   unsigned int relation);





/* pass an event to the cpufreq governor */

int cpufreq_governor(unsigned int cpu, unsigned int event);



int cpufreq_register_governor(struct cpufreq_governor *governor);

void cpufreq_unregister_governor(struct cpufreq_governor *governor);

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