4 files changed, 175 insertions, 215 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 1ba4039777e..b3df613ae4e 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -284,39 +284,69 @@ EXPORT_SYMBOL_GPL(cpufreq_notify_transition);
  *                          SYSFS INTERFACE                          *
  *********************************************************************/
 
+static struct cpufreq_governor *__find_governor(const char *str_governor)
+{
+	struct cpufreq_governor *t;
+
+	list_for_each_entry(t, &cpufreq_governor_list, governor_list)
+		if (!strnicmp(str_governor,t->name,CPUFREQ_NAME_LEN))
+			return t;
+
+	return NULL;
+}
+
 /**
  * cpufreq_parse_governor - parse a governor string
  */
 static int cpufreq_parse_governor (char *str_governor, unsigned int *policy,
 				struct cpufreq_governor **governor)
 {
+	int err = -EINVAL;
+
 	if (!cpufreq_driver)
-		return -EINVAL;
+		goto out;
+
 	if (cpufreq_driver->setpolicy) {
 		if (!strnicmp(str_governor, "performance", CPUFREQ_NAME_LEN)) {
 			*policy = CPUFREQ_POLICY_PERFORMANCE;
-			return 0;
+			err = 0;
 		} else if (!strnicmp(str_governor, "powersave", CPUFREQ_NAME_LEN)) {
 			*policy = CPUFREQ_POLICY_POWERSAVE;
-			return 0;
+			err = 0;
 		}
-		return -EINVAL;
-	} else {
+	} else if (cpufreq_driver->target) {
 		struct cpufreq_governor *t;
+
 		mutex_lock(&cpufreq_governor_mutex);
-		if (!cpufreq_driver || !cpufreq_driver->target)
-			goto out;
-		list_for_each_entry(t, &cpufreq_governor_list, governor_list) {
-			if (!strnicmp(str_governor,t->name,CPUFREQ_NAME_LEN)) {
-				*governor = t;
+
+		t = __find_governor(str_governor);
+
+		if (t == NULL) {
+			char *name = kasprintf(GFP_KERNEL, "cpufreq_%s", str_governor);
+
+			if (name) {
+				int ret;
+
 				mutex_unlock(&cpufreq_governor_mutex);
-				return 0;
+				ret = request_module(name);
+				mutex_lock(&cpufreq_governor_mutex);
+
+				if (ret == 0)
+					t = __find_governor(str_governor);
 			}
+
+			kfree(name);
 		}
-out:
+
+		if (t != NULL) {
+			*governor = t;
+			err = 0;
+		}
+
 		mutex_unlock(&cpufreq_governor_mutex);
 	}
-	return -EINVAL;
+  out:
+	return err;
 }
 
 
@@ -364,10 +394,12 @@ 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;					\
 }
@@ -423,6 +455,8 @@ static ssize_t store_scaling_governor (struct cpufreq_policy * policy,
 	if (cpufreq_parse_governor(str_governor, &new_policy.policy, &new_policy.governor))
 		return -EINVAL;
 
+	lock_cpu_hotplug();
+
 	/* Do not use cpufreq_set_policy here or the user_policy.max
 	   will be wrongly overridden */
 	mutex_lock(&policy->lock);
@@ -432,6 +466,8 @@ static ssize_t store_scaling_governor (struct cpufreq_policy * policy,
 	policy->user_policy.governor = policy->governor;
 	mutex_unlock(&policy->lock);
 
+	unlock_cpu_hotplug();
+
 	return ret ? ret : count;
 }
 
@@ -1193,20 +1229,18 @@ 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);
@@ -1221,17 +1255,23 @@ 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)
 {
@@ -1253,43 +1293,23 @@ 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;
+	int err;
 
 	if (!governor)
 		return -EINVAL;
 
 	mutex_lock(&cpufreq_governor_mutex);
 
-	list_for_each_entry(t, &cpufreq_governor_list, governor_list) {
-		if (!strnicmp(governor->name,t->name,CPUFREQ_NAME_LEN)) {
-			mutex_unlock(&cpufreq_governor_mutex);
-			return -EBUSY;
-		}
+	err = -EBUSY;
+	if (__find_governor(governor->name) == NULL) {
+		err = 0;
+		list_add(&governor->governor_list, &cpufreq_governor_list);
 	}
-	list_add(&governor->governor_list, &cpufreq_governor_list);
 
 	mutex_unlock(&cpufreq_governor_mutex);
-	return 0;
+	return err;
 }
 EXPORT_SYMBOL_GPL(cpufreq_register_governor);
 
@@ -1338,6 +1358,9 @@ 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;
@@ -1348,6 +1371,11 @@ static int __cpufreq_set_policy(struct cpufreq_policy *data, struct cpufreq_poli
 
 	memcpy(&policy->cpuinfo, &data->cpuinfo, sizeof(struct cpufreq_cpuinfo));
 
+	if (policy->min > data->min && policy->min > policy->max) {
+		ret = -EINVAL;
+		goto error_out;
+	}
+
 	/* verify the cpu speed can be set within this limit */
 	ret = cpufreq_driver->verify(policy);
 	if (ret)
@@ -1432,6 +1460,8 @@ int cpufreq_set_policy(struct cpufreq_policy *policy)
 	if (!data)
 		return -EINVAL;
 
+	lock_cpu_hotplug();
+
 	/* lock this CPU */
 	mutex_lock(&data->lock);
 
@@ -1442,6 +1472,8 @@ 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;
@@ -1465,6 +1497,7 @@ 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);
@@ -1490,7 +1523,7 @@ 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;
 }
diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
index b3ebc8f0197..c4c578defab 100644
--- a/drivers/cpufreq/cpufreq_conservative.c
+++ b/drivers/cpufreq/cpufreq_conservative.c
@@ -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;
diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 693e540481b..52cf1f02182 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -12,22 +12,11 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
-#include <linux/smp.h>
 #include <linux/init.h>
-#include <linux/interrupt.h>
-#include <linux/ctype.h>
 #include <linux/cpufreq.h>
-#include <linux/sysctl.h>
-#include <linux/types.h>
-#include <linux/fs.h>
-#include <linux/sysfs.h>
 #include <linux/cpu.h>
-#include <linux/sched.h>
-#include <linux/kmod.h>
-#include <linux/workqueue.h>
 #include <linux/jiffies.h>
 #include <linux/kernel_stat.h>
-#include <linux/percpu.h>
 #include <linux/mutex.h>
 
 /*
@@ -56,16 +45,15 @@ static unsigned int def_sampling_rate;
 #define MIN_SAMPLING_RATE			(def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
 #define MAX_SAMPLING_RATE			(500 * def_sampling_rate)
 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER	(1000)
-#define DEF_SAMPLING_DOWN_FACTOR		(1)
-#define MAX_SAMPLING_DOWN_FACTOR		(10)
 #define TRANSITION_LATENCY_LIMIT		(10 * 1000)
 
 static void do_dbs_timer(void *data);
 
 struct cpu_dbs_info_s {
+	cputime64_t prev_cpu_idle;
+	cputime64_t prev_cpu_wall;
 	struct cpufreq_policy *cur_policy;
-	unsigned int prev_cpu_idle_up;
-	unsigned int prev_cpu_idle_down;
+ 	struct work_struct work;
 	unsigned int enable;
 };
 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
@@ -80,31 +68,32 @@ static unsigned int dbs_enable;	/* number of CPUs using this policy */
  * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  * is recursive for the same process. -Venki
  */
-static DEFINE_MUTEX (dbs_mutex);
-static DECLARE_WORK	(dbs_work, do_dbs_timer, NULL);
+static DEFINE_MUTEX(dbs_mutex);
 
-static struct workqueue_struct *dbs_workq;
+static struct workqueue_struct	*kondemand_wq;
 
 struct dbs_tuners {
 	unsigned int sampling_rate;
-	unsigned int sampling_down_factor;
 	unsigned int up_threshold;
 	unsigned int ignore_nice;
 };
 
 static struct dbs_tuners dbs_tuners_ins = {
 	.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
-	.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
 	.ignore_nice = 0,
 };
 
-static inline unsigned int get_cpu_idle_time(unsigned int cpu)
+static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
 {
-	return	kstat_cpu(cpu).cpustat.idle +
-		kstat_cpu(cpu).cpustat.iowait +
-		( dbs_tuners_ins.ignore_nice ?
-		  kstat_cpu(cpu).cpustat.nice :
-		  0);
+	cputime64_t retval;
+
+	retval = cputime64_add(kstat_cpu(cpu).cpustat.idle,
+			kstat_cpu(cpu).cpustat.iowait);
+
+	if (dbs_tuners_ins.ignore_nice)
+		retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice);
+
+	return retval;
 }
 
 /************************** sysfs interface ************************/
@@ -133,35 +122,15 @@ static ssize_t show_##file_name						\
 	return sprintf(buf, "%u\n", dbs_tuners_ins.object);		\
 }
 show_one(sampling_rate, sampling_rate);
-show_one(sampling_down_factor, sampling_down_factor);
 show_one(up_threshold, up_threshold);
 show_one(ignore_nice_load, ignore_nice);
 
-static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
-		const char *buf, size_t count)
-{
-	unsigned int input;
-	int ret;
-	ret = sscanf (buf, "%u", &input);
-	if (ret != 1 )
-		return -EINVAL;
-
-	if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
-		return -EINVAL;
-
-	mutex_lock(&dbs_mutex);
-	dbs_tuners_ins.sampling_down_factor = input;
-	mutex_unlock(&dbs_mutex);
-
-	return count;
-}
-
 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 		const char *buf, size_t count)
 {
 	unsigned int input;
 	int ret;
-	ret = sscanf (buf, "%u", &input);
+	ret = sscanf(buf, "%u", &input);
 
 	mutex_lock(&dbs_mutex);
 	if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
@@ -180,7 +149,7 @@ static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 {
 	unsigned int input;
 	int ret;
-	ret = sscanf (buf, "%u", &input);
+	ret = sscanf(buf, "%u", &input);
 
 	mutex_lock(&dbs_mutex);
 	if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
@@ -203,7 +172,7 @@ static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 
 	unsigned int j;
 
-	ret = sscanf (buf, "%u", &input);
+	ret = sscanf(buf, "%u", &input);
 	if ( ret != 1 )
 		return -EINVAL;
 
@@ -217,12 +186,12 @@ static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 	}
 	dbs_tuners_ins.ignore_nice = input;
 
-	/* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
+	/* we need to re-evaluate prev_cpu_idle */
 	for_each_online_cpu(j) {
-		struct cpu_dbs_info_s *j_dbs_info;
-		j_dbs_info = &per_cpu(cpu_dbs_info, j);
-		j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
-		j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
+		struct cpu_dbs_info_s *dbs_info;
+		dbs_info = &per_cpu(cpu_dbs_info, j);
+		dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
+		dbs_info->prev_cpu_wall = get_jiffies_64();
 	}
 	mutex_unlock(&dbs_mutex);
 
@@ -234,7 +203,6 @@ static struct freq_attr _name = \
 __ATTR(_name, 0644, show_##_name, store_##_name)
 
 define_one_rw(sampling_rate);
-define_one_rw(sampling_down_factor);
 define_one_rw(up_threshold);
 define_one_rw(ignore_nice_load);
 
@@ -242,7 +210,6 @@ static struct attribute * dbs_attributes[] = {
 	&sampling_rate_max.attr,
 	&sampling_rate_min.attr,
 	&sampling_rate.attr,
-	&sampling_down_factor.attr,
 	&up_threshold.attr,
 	&ignore_nice_load.attr,
 	NULL
@@ -255,26 +222,29 @@ static struct attribute_group dbs_attr_group = {
 
 /************************** sysfs end ************************/
 
-static void dbs_check_cpu(int cpu)
+static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
 {
-	unsigned int idle_ticks, up_idle_ticks, total_ticks;
-	unsigned int freq_next;
-	unsigned int freq_down_sampling_rate;
-	static int down_skip[NR_CPUS];
-	struct cpu_dbs_info_s *this_dbs_info;
+	unsigned int idle_ticks, total_ticks;
+	unsigned int load;
+	cputime64_t cur_jiffies;
 
 	struct cpufreq_policy *policy;
 	unsigned int j;
 
-	this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 	if (!this_dbs_info->enable)
 		return;
 
 	policy = this_dbs_info->cur_policy;
+	cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
+	total_ticks = (unsigned int) cputime64_sub(cur_jiffies,
+			this_dbs_info->prev_cpu_wall);
+	this_dbs_info->prev_cpu_wall = cur_jiffies;
+	if (!total_ticks)
+		return;
 	/*
 	 * Every sampling_rate, we check, if current idle time is less
 	 * than 20% (default), then we try to increase frequency
-	 * Every sampling_rate*sampling_down_factor, we look for a the lowest
+	 * Every sampling_rate, we look for a the lowest
 	 * frequency which can sustain the load while keeping idle time over
 	 * 30%. If such a frequency exist, we try to decrease to this frequency.
 	 *
@@ -283,36 +253,26 @@ static void dbs_check_cpu(int cpu)
 	 * 5% (default) of current frequency
 	 */
 
-	/* Check for frequency increase */
+	/* Get Idle Time */
 	idle_ticks = UINT_MAX;
 	for_each_cpu_mask(j, policy->cpus) {
-		unsigned int tmp_idle_ticks, total_idle_ticks;
+		cputime64_t total_idle_ticks;
+		unsigned int tmp_idle_ticks;
 		struct cpu_dbs_info_s *j_dbs_info;
 
 		j_dbs_info = &per_cpu(cpu_dbs_info, j);
 		total_idle_ticks = get_cpu_idle_time(j);
-		tmp_idle_ticks = total_idle_ticks -
-			j_dbs_info->prev_cpu_idle_up;
-		j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
+		tmp_idle_ticks = (unsigned int) cputime64_sub(total_idle_ticks,
+				j_dbs_info->prev_cpu_idle);
+		j_dbs_info->prev_cpu_idle = total_idle_ticks;
 
 		if (tmp_idle_ticks < idle_ticks)
 			idle_ticks = tmp_idle_ticks;
 	}
+	load = (100 * (total_ticks - idle_ticks)) / total_ticks;
 
-	/* Scale idle ticks by 100 and compare with up and down ticks */
-	idle_ticks *= 100;
-	up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
-			usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
-
-	if (idle_ticks < up_idle_ticks) {
-		down_skip[cpu] = 0;
-		for_each_cpu_mask(j, policy->cpus) {
-			struct cpu_dbs_info_s *j_dbs_info;
-
-			j_dbs_info = &per_cpu(cpu_dbs_info, j);
-			j_dbs_info->prev_cpu_idle_down =
-					j_dbs_info->prev_cpu_idle_up;
-		}
+	/* Check for frequency increase */
+	if (load > dbs_tuners_ins.up_threshold) {
 		/* if we are already at full speed then break out early */
 		if (policy->cur == policy->max)
 			return;
@@ -323,83 +283,54 @@ static void dbs_check_cpu(int cpu)
 	}
 
 	/* Check for frequency decrease */
-	down_skip[cpu]++;
-	if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
-		return;
-
-	idle_ticks = UINT_MAX;
-	for_each_cpu_mask(j, policy->cpus) {
-		unsigned int tmp_idle_ticks, total_idle_ticks;
-		struct cpu_dbs_info_s *j_dbs_info;
-
-		j_dbs_info = &per_cpu(cpu_dbs_info, j);
-		/* Check for frequency decrease */
-		total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
-		tmp_idle_ticks = total_idle_ticks -
-			j_dbs_info->prev_cpu_idle_down;
-		j_dbs_info->prev_cpu_idle_down = total_idle_ticks;
-
-		if (tmp_idle_ticks < idle_ticks)
-			idle_ticks = tmp_idle_ticks;
-	}
-
-	down_skip[cpu] = 0;
 	/* if we cannot reduce the frequency anymore, break out early */
 	if (policy->cur == policy->min)
 		return;
 
-	/* Compute how many ticks there are between two measurements */
-	freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
-		dbs_tuners_ins.sampling_down_factor;
-	total_ticks = usecs_to_jiffies(freq_down_sampling_rate);
-
 	/*
 	 * The optimal frequency is the frequency that is the lowest that
 	 * can support the current CPU usage without triggering the up
 	 * policy. To be safe, we focus 10 points under the threshold.
 	 */
-	freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
-	freq_next = (freq_next * policy->cur) /
+	if (load < (dbs_tuners_ins.up_threshold - 10)) {
+		unsigned int freq_next;
+		freq_next = (policy->cur * load) /
 			(dbs_tuners_ins.up_threshold - 10);
 
-	if (freq_next < policy->min)
-		freq_next = policy->min;
-
-	if (freq_next <= ((policy->cur * 95) / 100))
 		__cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
+	}
 }
 
 static void do_dbs_timer(void *data)
 {
-	int i;
+	unsigned int cpu = smp_processor_id();
+	struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
+
+	if (!dbs_info->enable)
+		return;
+
 	lock_cpu_hotplug();
-	mutex_lock(&dbs_mutex);
-	for_each_online_cpu(i)
-		dbs_check_cpu(i);
-	queue_delayed_work(dbs_workq, &dbs_work,
-			   usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
-	mutex_unlock(&dbs_mutex);
+	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));
 }
 
-static inline void dbs_timer_init(void)
+static inline void dbs_timer_init(unsigned int cpu)
 {
-	INIT_WORK(&dbs_work, do_dbs_timer, NULL);
-	if (!dbs_workq)
-		dbs_workq = create_singlethread_workqueue("ondemand");
-	if (!dbs_workq) {
-		printk(KERN_ERR "ondemand: Cannot initialize kernel thread\n");
-		return;
-	}
-	queue_delayed_work(dbs_workq, &dbs_work,
-			   usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
+	struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
+
+	INIT_WORK(&dbs_info->work, do_dbs_timer, 0);
+	queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work,
+			usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 	return;
 }
 
-static inline void dbs_timer_exit(void)
+static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 {
-	if (dbs_workq)
-		cancel_rearming_delayed_workqueue(dbs_workq, &dbs_work);
+	dbs_info->enable = 0;
+	cancel_delayed_work(&dbs_info->work);
+	flush_workqueue(kondemand_wq);
 }
 
 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
@@ -413,8 +344,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 
 	switch (event) {
 	case CPUFREQ_GOV_START:
-		if ((!cpu_online(cpu)) ||
-		    (!policy->cur))
+		if ((!cpu_online(cpu)) || (!policy->cur))
 			return -EINVAL;
 
 		if (policy->cpuinfo.transition_latency >
@@ -427,18 +357,26 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 			break;
 
 		mutex_lock(&dbs_mutex);
+		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;
+			}
+		}
 		for_each_cpu_mask(j, policy->cpus) {
 			struct cpu_dbs_info_s *j_dbs_info;
 			j_dbs_info = &per_cpu(cpu_dbs_info, j);
 			j_dbs_info->cur_policy = policy;
 
-			j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
-			j_dbs_info->prev_cpu_idle_down
-				= j_dbs_info->prev_cpu_idle_up;
+			j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
+			j_dbs_info->prev_cpu_wall = get_jiffies_64();
 		}
 		this_dbs_info->enable = 1;
 		sysfs_create_group(&policy->kobj, &dbs_attr_group);
-		dbs_enable++;
 		/*
 		 * Start the timerschedule work, when this governor
 		 * is used for first time
@@ -457,50 +395,44 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 				def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 
 			dbs_tuners_ins.sampling_rate = def_sampling_rate;
-			dbs_timer_init();
 		}
+		dbs_timer_init(policy->cpu);
 
 		mutex_unlock(&dbs_mutex);
 		break;
 
 	case CPUFREQ_GOV_STOP:
 		mutex_lock(&dbs_mutex);
-		this_dbs_info->enable = 0;
+		dbs_timer_exit(this_dbs_info);
 		sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 		dbs_enable--;
-		/*
-		 * Stop the timerschedule work, when this governor
-		 * is used for first time
-		 */
 		if (dbs_enable == 0)
-			dbs_timer_exit();
+			destroy_workqueue(kondemand_wq);
 
 		mutex_unlock(&dbs_mutex);
 
 		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,
-					policy->max, CPUFREQ_RELATION_H);
+			__cpufreq_driver_target(this_dbs_info->cur_policy,
+			                        policy->max,
+			                        CPUFREQ_RELATION_H);
 		else if (policy->min > this_dbs_info->cur_policy->cur)
-			__cpufreq_driver_target(
-					this_dbs_info->cur_policy,
-					policy->min, CPUFREQ_RELATION_L);
+			__cpufreq_driver_target(this_dbs_info->cur_policy,
+			                        policy->min,
+			                        CPUFREQ_RELATION_L);
 		mutex_unlock(&dbs_mutex);
-		unlock_cpu_hotplug();
 		break;
 	}
 	return 0;
 }
 
 static struct cpufreq_governor cpufreq_gov_dbs = {
-	.name		= "ondemand",
-	.governor	= cpufreq_governor_dbs,
-	.owner		= THIS_MODULE,
+	.name = "ondemand",
+	.governor = cpufreq_governor_dbs,
+	.owner = THIS_MODULE,
 };
 
 static int __init cpufreq_gov_dbs_init(void)
@@ -510,21 +442,15 @@ static int __init cpufreq_gov_dbs_init(void)
 
 static void __exit cpufreq_gov_dbs_exit(void)
 {
-	/* Make sure that the scheduled work is indeed not running.
-	   Assumes the timer has been cancelled first. */
-	if (dbs_workq) {
-		flush_workqueue(dbs_workq);
-		destroy_workqueue(dbs_workq);
-	}
-
 	cpufreq_unregister_governor(&cpufreq_gov_dbs);
 }
 
 
-MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
-MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for "
-		"Low Latency Frequency Transition capable processors");
-MODULE_LICENSE ("GPL");
+MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
+MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
+MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
+                   "Low Latency Frequency Transition capable processors");
+MODULE_LICENSE("GPL");
 
 module_init(cpufreq_gov_dbs_init);
 module_exit(cpufreq_gov_dbs_exit);
diff --git a/drivers/cpufreq/cpufreq_userspace.c b/drivers/cpufreq/cpufreq_userspace.c
index 44ae5e5b94c..a06c204589c 100644
--- a/drivers/cpufreq/cpufreq_userspace.c
+++ b/drivers/cpufreq/cpufreq_userspace.c
@@ -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;
 }