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Commit 9795607d authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki
Browse files

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: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 10b81821

drivers/cpufreq/cpufreq_stats.c

+7 −2
Original line number Diff line number Diff line
@@ -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);

}