cpufreq: stats: Fix concurrency issues while resetting stats

It is possible for cpufreq_stats_clear_table() and
cpufreq_stats_record_transition() to get called concurrently and they
will try to update same variables simultaneously and may lead to
corruption of data.

Prevent that with the help of existing spinlock.

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 941e63e3e652e6057323555b605305839a93a1f3..e2db5581489a03a4db6b91791e4deaec44c7e33a 100644 (file)
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -31,20 +31,20 @@ static void cpufreq_stats_update(struct cpufreq_stats *stats)
 {
        unsigned long long cur_time = get_jiffies_64();
 
-       spin_lock(&cpufreq_stats_lock);
        stats->time_in_state[stats->last_index] += cur_time - stats->last_time;
        stats->last_time = cur_time;
-       spin_unlock(&cpufreq_stats_lock);
 }
 
 static void cpufreq_stats_clear_table(struct cpufreq_stats *stats)
 {
        unsigned int count = stats->max_state;
 
+       spin_lock(&cpufreq_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);
 }
 
 static ssize_t show_total_trans(struct cpufreq_policy *policy, char *buf)
@@ -62,7 +62,10 @@ 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);
        cpufreq_stats_update(stats);
+       spin_unlock(&cpufreq_stats_lock);
+
        for (i = 0; i < stats->state_num; i++) {
                len += sprintf(buf + len, "%u %llu\n", stats->freq_table[i],
                        (unsigned long long)
@@ -239,9 +242,11 @@ 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);
        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);
 }