cpufreq: use system_wq instead of dedicated workqueues

With cmwq, there's no reason for cpufreq drivers to use separate
workqueues.  Remove the dedicated workqueues from cpufreq_conservative
and cpufreq_ondemand and use system_wq instead.  The work items are
already sync canceled on stop, so it's already guaranteed that no work
is running on module exit.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Dave Jones <davej@redhat.com>
Cc: cpufreq@vger.kernel.org

drivers/cpufreq/cpufreq_conservative.c

@@ -81,8 +81,6 @@ static unsigned int dbs_enable;	/* number of CPUs using this policy */
  */
 static DEFINE_MUTEX(dbs_mutex);
 
-static struct workqueue_struct	*kconservative_wq;
-
 static struct dbs_tuners {
 	unsigned int sampling_rate;
 	unsigned int sampling_down_factor;
@@ -560,7 +558,7 @@ static void do_dbs_timer(struct work_struct *work)
 
 	dbs_check_cpu(dbs_info);
 
-	queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
+	schedule_delayed_work_on(cpu, &dbs_info->work, delay);
 	mutex_unlock(&dbs_info->timer_mutex);
 }
 
@@ -572,8 +570,7 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 
 	dbs_info->enable = 1;
 	INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
-	queue_delayed_work_on(dbs_info->cpu, kconservative_wq, &dbs_info->work,
-				delay);
+	schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
 }
 
 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
@@ -716,25 +713,12 @@ struct cpufreq_governor cpufreq_gov_conservative = {
 
 static int __init cpufreq_gov_dbs_init(void)
 {
-	int err;
-
-	kconservative_wq = create_workqueue("kconservative");
-	if (!kconservative_wq) {
-		printk(KERN_ERR "Creation of kconservative failed\n");
-		return -EFAULT;
-	}
-
-	err = cpufreq_register_governor(&cpufreq_gov_conservative);
-	if (err)
-		destroy_workqueue(kconservative_wq);
-
-	return err;
+	return cpufreq_register_governor(&cpufreq_gov_conservative);
 }
 
 static void __exit cpufreq_gov_dbs_exit(void)
 {
 	cpufreq_unregister_governor(&cpufreq_gov_conservative);
-	destroy_workqueue(kconservative_wq);
 }
 
 

drivers/cpufreq/cpufreq_ondemand.c

@@ -104,8 +104,6 @@ static unsigned int dbs_enable;	/* number of CPUs using this policy */
  */
 static DEFINE_MUTEX(dbs_mutex);
 
-static struct workqueue_struct	*kondemand_wq;
-
 static struct dbs_tuners {
 	unsigned int sampling_rate;
 	unsigned int up_threshold;
@@ -667,7 +665,7 @@ static void do_dbs_timer(struct work_struct *work)
 		__cpufreq_driver_target(dbs_info->cur_policy,
 			dbs_info->freq_lo, CPUFREQ_RELATION_H);
 	}
-	queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
+	schedule_delayed_work_on(cpu, &dbs_info->work, delay);
 	mutex_unlock(&dbs_info->timer_mutex);
 }
 
@@ -681,8 +679,7 @@ static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
 
 	dbs_info->sample_type = DBS_NORMAL_SAMPLE;
 	INIT_DELAYED_WORK_DEFERRABLE(&dbs_info->work, do_dbs_timer);
-	queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,
-		delay);
+	schedule_delayed_work_on(dbs_info->cpu, &dbs_info->work, delay);
 }
 
 static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
@@ -814,7 +811,6 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 
 static int __init cpufreq_gov_dbs_init(void)
 {
-	int err;
 	cputime64_t wall;
 	u64 idle_time;
 	int cpu = get_cpu();
@@ -838,22 +834,12 @@ static int __init cpufreq_gov_dbs_init(void)
 			MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10);
 	}
 
-	kondemand_wq = create_workqueue("kondemand");
-	if (!kondemand_wq) {
-		printk(KERN_ERR "Creation of kondemand failed\n");
-		return -EFAULT;
-	}
-	err = cpufreq_register_governor(&cpufreq_gov_ondemand);
-	if (err)
-		destroy_workqueue(kondemand_wq);
-
-	return err;
+	return cpufreq_register_governor(&cpufreq_gov_ondemand);
 }
 
 static void __exit cpufreq_gov_dbs_exit(void)
 {
 	cpufreq_unregister_governor(&cpufreq_gov_ondemand);
-	destroy_workqueue(kondemand_wq);
 }