3 files changed, 31 insertions, 26 deletions

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 6c6121b85a5..23a63207d74 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -38,7 +38,6 @@ static struct cpufreq_driver   	*cpufreq_driver;
 static struct cpufreq_policy	*cpufreq_cpu_data[NR_CPUS];
 static DEFINE_SPINLOCK(cpufreq_driver_lock);
 
-
 /* internal prototypes */
 static int __cpufreq_governor(struct cpufreq_policy *policy, unsigned int event);
 static void handle_update(void *data);
@@ -593,12 +592,11 @@ static int cpufreq_add_dev (struct sys_device * sys_dev)
 		goto module_out;
 	}
 
-	policy = kmalloc(sizeof(struct cpufreq_policy), GFP_KERNEL);
+	policy = kzalloc(sizeof(struct cpufreq_policy), GFP_KERNEL);
 	if (!policy) {
 		ret = -ENOMEM;
 		goto nomem_out;
 	}
-	memset(policy, 0, sizeof(struct cpufreq_policy));
 
 	policy->cpu = cpu;
 	policy->cpus = cpumask_of_cpu(cpu);
@@ -1116,24 +1114,21 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
 	int retval = -EINVAL;
 
 	/*
-	 * Converted the lock_cpu_hotplug to preempt_disable()
-	 * and preempt_enable(). This is a bit kludgy and relies on how cpu
-	 * hotplug works. All we need is a guarantee that cpu hotplug won't make
-	 * progress on any cpu. Once we do preempt_disable(), this would ensure
-	 * that hotplug threads don't get onto this cpu, thereby delaying
-	 * the cpu remove process.
-	 *
-	 * We removed the lock_cpu_hotplug since we need to call this function
-	 * via cpu hotplug callbacks, which result in locking the cpu hotplug
-	 * thread itself. Agree this is not very clean, cpufreq community
-	 * could improve this if required. - Ashok Raj <ashok.raj@intel.com>
+	 * If we are already in context of hotplug thread, we dont need to
+	 * acquire the hotplug lock. Otherwise acquire cpucontrol to prevent
+	 * hotplug from removing this cpu that we are working on.
 	 */
-	preempt_disable();
+	if (!current_in_cpu_hotplug())
+		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);
-	preempt_enable();
+
+	if (!current_in_cpu_hotplug())
+		unlock_cpu_hotplug();
+
 	return retval;
 }
 EXPORT_SYMBOL_GPL(__cpufreq_driver_target);
diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index c1fc9c62bb5..17741111246 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -48,7 +48,10 @@
  * All times here are in uS.
  */
 static unsigned int 				def_sampling_rate;
-#define MIN_SAMPLING_RATE			(def_sampling_rate / 2)
+#define MIN_SAMPLING_RATE_RATIO			(2)
+/* for correct statistics, we need at least 10 ticks between each measure */
+#define MIN_STAT_SAMPLING_RATE			(MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
+#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)
@@ -416,13 +419,16 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 		if (dbs_enable == 1) {
 			unsigned int latency;
 			/* policy latency is in nS. Convert it to uS first */
+			latency = policy->cpuinfo.transition_latency / 1000;
+			if (latency == 0)
+				latency = 1;
 
-			latency = policy->cpuinfo.transition_latency;
-			if (latency < 1000)
-				latency = 1000;
-
-			def_sampling_rate = (latency / 1000) *
+			def_sampling_rate = latency *
 					DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
+
+			if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
+				def_sampling_rate = MIN_STAT_SAMPLING_RATE;
+
 			dbs_tuners_ins.sampling_rate = def_sampling_rate;
 			dbs_tuners_ins.ignore_nice = 0;
 
diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index 3597f25d5ef..0bddb8e694d 100644
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -193,11 +193,15 @@ cpufreq_stats_create_table (struct cpufreq_policy *policy,
 	unsigned int cpu = policy->cpu;
 	if (cpufreq_stats_table[cpu])
 		return -EBUSY;
-	if ((stat = kmalloc(sizeof(struct cpufreq_stats), GFP_KERNEL)) == NULL)
+	if ((stat = kzalloc(sizeof(struct cpufreq_stats), GFP_KERNEL)) == NULL)
 		return -ENOMEM;
-	memset(stat, 0, sizeof (struct cpufreq_stats));
 
 	data = cpufreq_cpu_get(cpu);
+	if (data == NULL) {
+		ret = -EINVAL;
+		goto error_get_fail;
+	}
+
 	if ((ret = sysfs_create_group(&data->kobj, &stats_attr_group)))
 		goto error_out;
 
@@ -217,12 +221,11 @@ cpufreq_stats_create_table (struct cpufreq_policy *policy,
 	alloc_size += count * count * sizeof(int);
 #endif
 	stat->max_state = count;
-	stat->time_in_state = kmalloc(alloc_size, GFP_KERNEL);
+	stat->time_in_state = kzalloc(alloc_size, GFP_KERNEL);
 	if (!stat->time_in_state) {
 		ret = -ENOMEM;
 		goto error_out;
 	}
-	memset(stat->time_in_state, 0, alloc_size);
 	stat->freq_table = (unsigned int *)(stat->time_in_state + count);
 
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
@@ -245,6 +248,7 @@ cpufreq_stats_create_table (struct cpufreq_policy *policy,
 	return 0;
 error_out:
 	cpufreq_cpu_put(data);
+error_get_fail:
 	kfree(stat);
 	cpufreq_stats_table[cpu] = NULL;
 	return ret;