cpufreq: stats: drop unnecessary locking

There is no possibility of any race on updating last_index, trans_table or
total_trans as these are updated only by cpufreq_stat_notifier_trans() which
will be called sequentially.

The only place where locking is still relevant is: cpufreq_stats_update(), which
updates time_in_state and last_time. This can be called by two thread in
parallel, that may result in races.

The two threads being:
- sysfs read of time_in_state
- and frequency transition that calls cpufreq_stat_notifier_trans().

Remove locking from the first case mentioned above.

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

diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index c948086a332bae702a5a6fc20b14a409e3d21f4f..5e370a30a964f5f30e9944daa9a768507c938af4 100644 (file)
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -207,12 +207,10 @@ static int __cpufreq_stats_create_table(struct cpufreq_policy *policy)
        cpufreq_for_each_valid_entry(pos, table)
                if (freq_table_get_index(stats, pos->frequency) == -1)
                        stats->freq_table[i++] = pos->frequency;
-       stats->state_num = i;
 
-       spin_lock(&cpufreq_stats_lock);
+       stats->state_num = i;
        stats->last_time = get_jiffies_64();
        stats->last_index = freq_table_get_index(stats, policy->cur);
-       spin_unlock(&cpufreq_stats_lock);
 
        policy->stats = stats;
        ret = sysfs_create_group(&policy->kobj, &stats_attr_group);
@@ -294,13 +292,11 @@ static int cpufreq_stat_notifier_trans(struct notifier_block *nb,
 
        cpufreq_stats_update(stats);
 
-       spin_lock(&cpufreq_stats_lock);
        stats->last_index = new_index;
 #ifdef CONFIG_CPU_FREQ_STAT_DETAILS
        stats->trans_table[old_index * stats->max_state + new_index]++;
 #endif
        stats->total_trans++;
-       spin_unlock(&cpufreq_stats_lock);
 
 put_policy:
        cpufreq_cpu_put(policy);