diff options
| -rw-r--r-- | drivers/cpufreq/cpufreq_stats.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c index 8e7d64f34041..1b1389face85 100644 --- a/drivers/cpufreq/cpufreq_stats.c +++ b/drivers/cpufreq/cpufreq_stats.c @@ -47,6 +47,11 @@ static void cpufreq_stats_reset_table(struct cpufreq_stats *stats) /* Adjust for the time elapsed since reset was requested */ WRITE_ONCE(stats->reset_pending, 0); + /* + * Prevent the reset_time read from being reordered before the + * reset_pending accesses in cpufreq_stats_record_transition(). + */ + smp_rmb(); cpufreq_stats_update(stats, READ_ONCE(stats->reset_time)); } @@ -71,10 +76,16 @@ static ssize_t show_time_in_state(struct cpufreq_policy *policy, char *buf) for (i = 0; i < stats->state_num; i++) { if (pending) { - if (i == stats->last_index) + if (i == stats->last_index) { + /* + * Prevent the reset_time read from occurring + * before the reset_pending read above. + */ + smp_rmb(); time = get_jiffies_64() - READ_ONCE(stats->reset_time); - else + } else { time = 0; + } } else { time = stats->time_in_state[i]; if (i == stats->last_index) @@ -99,6 +110,11 @@ static ssize_t store_reset(struct cpufreq_policy *policy, const char *buf, * avoid races. */ WRITE_ONCE(stats->reset_time, get_jiffies_64()); + /* + * The memory barrier below is to prevent the readers of reset_time from + * seeing a stale or partially updated value. + */ + smp_wmb(); WRITE_ONCE(stats->reset_pending, 1); return count; |