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Commit 56463b78 authored by Venkatesh Pallipadi's avatar Venkatesh Pallipadi Committed by Dave Jones
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[CPUFREQ] ondemand governor use new cpufreq rwsem locking in work callback 

Eliminate flush_workqueue in cpufreq_governor(STOP) callpath. Using flush
there has a deadlock potential as in

http://uwsg.iu.edu/hypermail/linux/kernel/0611.3/1223.html



Also, cleanup the locking issues with do_dbs_timer delayed_work callback.  As
it changes the CPU frequency using __cpufreq_target, it needs to have
policy_rwsem in write mode, which also protects it from hot plug.

Signed-off-by: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDave Jones <davej@redhat.com>
parent 529af7a1

drivers/cpufreq/cpufreq_ondemand.c

+16 −18
Original line number Original line Diff line number Diff line
@@ -437,8 +437,14 @@ static void do_dbs_timer(struct work_struct *work) 




	delay -= jiffies % delay;

	delay -= jiffies % delay;





	if (!dbs_info->enable)

	if (lock_policy_rwsem_write(cpu) < 0)

		return;

		return;



	if (!dbs_info->enable) {

		unlock_policy_rwsem_write(cpu);

		return;

	}



	/* Common NORMAL_SAMPLE setup */

	/* Common NORMAL_SAMPLE setup */

	dbs_info->sample_type = DBS_NORMAL_SAMPLE;

	dbs_info->sample_type = DBS_NORMAL_SAMPLE;

	if (!dbs_tuners_ins.powersave_bias ||

	if (!dbs_tuners_ins.powersave_bias ||
@@ -455,6 +461,7 @@ static void do_dbs_timer(struct work_struct *work) 
	                        	CPUFREQ_RELATION_H);

	                        	CPUFREQ_RELATION_H);

	}

	}

	queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);

	queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);

	unlock_policy_rwsem_write(cpu);

}

}





static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)

static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
@@ -463,6 +470,7 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info) 
	int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

	int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

	delay -= jiffies % delay;

	delay -= jiffies % delay;





 	dbs_info->enable = 1;

	ondemand_powersave_bias_init();

	ondemand_powersave_bias_init();

	dbs_info->sample_type = DBS_NORMAL_SAMPLE;

	dbs_info->sample_type = DBS_NORMAL_SAMPLE;

	INIT_DELAYED_WORK_NAR(&dbs_info->work, do_dbs_timer);

	INIT_DELAYED_WORK_NAR(&dbs_info->work, do_dbs_timer);
@@ -474,7 +482,6 @@ static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info) 
{

{

	dbs_info->enable = 0;

	dbs_info->enable = 0;

	cancel_delayed_work(&dbs_info->work);

	cancel_delayed_work(&dbs_info->work);

	flush_workqueue(kondemand_wq);

}

}





static int cpufreq_governor_dbs(struct cpufreq_policy *policy,

static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
@@ -503,21 +510,9 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 




		mutex_lock(&dbs_mutex);

		mutex_lock(&dbs_mutex);

		dbs_enable++;

		dbs_enable++;

		if (dbs_enable == 1) {

			kondemand_wq = create_workqueue("kondemand");

			if (!kondemand_wq) {

				printk(KERN_ERR

					 "Creation of kondemand failed\n");

				dbs_enable--;

				mutex_unlock(&dbs_mutex);

				return -ENOSPC;

			}

		}





		rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);

		rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);

		if (rc) {

		if (rc) {

			if (dbs_enable == 1)

				destroy_workqueue(kondemand_wq);

			dbs_enable--;

			dbs_enable--;

			mutex_unlock(&dbs_mutex);

			mutex_unlock(&dbs_mutex);

			return rc;

			return rc;
@@ -532,7 +527,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 
			j_dbs_info->prev_cpu_wall = get_jiffies_64();

			j_dbs_info->prev_cpu_wall = get_jiffies_64();

		}

		}

		this_dbs_info->cpu = cpu;

		this_dbs_info->cpu = cpu;

		this_dbs_info->enable = 1;

		/*

		/*

		 * Start the timerschedule work, when this governor

		 * Start the timerschedule work, when this governor

		 * is used for first time

		 * is used for first time
@@ -562,9 +556,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 
		dbs_timer_exit(this_dbs_info);

		dbs_timer_exit(this_dbs_info);

		sysfs_remove_group(&policy->kobj, &dbs_attr_group);

		sysfs_remove_group(&policy->kobj, &dbs_attr_group);

		dbs_enable--;

		dbs_enable--;

		if (dbs_enable == 0)

			destroy_workqueue(kondemand_wq);



		mutex_unlock(&dbs_mutex);

		mutex_unlock(&dbs_mutex);





		break;

		break;
@@ -593,12 +584,18 @@ static struct cpufreq_governor cpufreq_gov_dbs = { 




static int __init cpufreq_gov_dbs_init(void)

static int __init cpufreq_gov_dbs_init(void)

{

{

	kondemand_wq = create_workqueue("kondemand");

	if (!kondemand_wq) {

		printk(KERN_ERR "Creation of kondemand failed\n");

		return -EFAULT;

	}

	return cpufreq_register_governor(&cpufreq_gov_dbs);

	return cpufreq_register_governor(&cpufreq_gov_dbs);

}

}





static void __exit cpufreq_gov_dbs_exit(void)

static void __exit cpufreq_gov_dbs_exit(void)

{

{

	cpufreq_unregister_governor(&cpufreq_gov_dbs);

	cpufreq_unregister_governor(&cpufreq_gov_dbs);

	destroy_workqueue(kondemand_wq);

}

}
@@ -610,3 +607,4 @@ MODULE_LICENSE("GPL"); 




module_init(cpufreq_gov_dbs_init);

module_init(cpufreq_gov_dbs_init);

module_exit(cpufreq_gov_dbs_exit);

module_exit(cpufreq_gov_dbs_exit);