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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>
This commit is contained in:
Viresh Kumar 2015-01-06 21:09:15 +05:30 committed by Rafael J. Wysocki
parent e73476949c
commit 490285c65e
1 changed files with 1 additions and 5 deletions
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6
drivers/cpufreq/cpufreq_stats.c
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@ -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);