cpufreq: stats: Use lock by stat to replace global spin lock

Stats is updated by each policy, using the lock by stat can
reduce the contention.

Signed-off-by: Kyle Lin <linkyle0915@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cpufreq_stats.c

@@ -14,7 +14,6 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 
-static DEFINE_SPINLOCK(cpufreq_stats_lock);
 
 struct cpufreq_stats {
 	unsigned int total_trans;
@@ -23,6 +22,7 @@ struct cpufreq_stats {
 	unsigned int state_num;
 	unsigned int last_index;
 	u64 *time_in_state;
+	spinlock_t lock;
 	unsigned int *freq_table;
 	unsigned int *trans_table;
 };
@@ -39,12 +39,12 @@ static void cpufreq_stats_clear_table(struct cpufreq_stats *stats)
 {
 	unsigned int count = stats->max_state;
 
-	spin_lock(&cpufreq_stats_lock);
+	spin_lock(&stats->lock);
 	memset(stats->time_in_state, 0, count * sizeof(u64));
 	memset(stats->trans_table, 0, count * count * sizeof(int));
 	stats->last_time = get_jiffies_64();
 	stats->total_trans = 0;
-	spin_unlock(&cpufreq_stats_lock);
+	spin_unlock(&stats->lock);
 }
 
 static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
@@ -62,9 +62,9 @@ static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf)
 	if (policy->fast_switch_enabled)
 		return 0;
 
-	spin_lock(&cpufreq_stats_lock);
+	spin_lock(&stats->lock);
 	cpufreq_stats_update(stats);
-	spin_unlock(&cpufreq_stats_lock);
+	spin_unlock(&stats->lock);
 
 	for (i = 0; i < stats->state_num; i++) {
 		len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i],
@@ -211,6 +211,7 @@ void cpufreq_stats_create_table(struct cpufreq_policy *policy)
 	stats->state_num = i;
 	stats->last_time = get_jiffies_64();
 	stats->last_index = freq_table_get_index(stats, policy->cur);
+	spin_lock_init(&stats->lock);
 
 	policy->stats = stats;
 	ret = sysfs_create_group(&policy->kobj, &stats_attr_group);
@@ -242,11 +243,11 @@ void cpufreq_stats_record_transition(struct cpufreq_policy *policy,
 	if (old_index == -1 || new_index == -1 || old_index == new_index)
 		return;
 
-	spin_lock(&cpufreq_stats_lock);
+	spin_lock(&stats->lock);
 	cpufreq_stats_update(stats);
 
 	stats->last_index = new_index;
 	stats->trans_table[old_index * stats->max_state + new_index]++;
 	stats->total_trans++;
-	spin_unlock(&cpufreq_stats_lock);
+	spin_unlock(&stats->lock);
 }