[PATCH 2/7] devfreq: protect devfreq stats data with spinlock

[Kamil Konieczny]

Protect access to devfreq transitions stats with spinlock.

Signed-off-by: Kamil Konieczny <k.konieczny@xxxxxxxxxxx>
---
 drivers/devfreq/devfreq.c | 18 +++++++++++++++---
 include/linux/devfreq.h   |  3 +++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 1602cca20fc4..ac04b5baef70 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -163,10 +163,16 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
 	cur_time = get_jiffies_64();
 
 	/* Immediately exit if previous_freq is not initialized yet. */
-	if (!devfreq->previous_freq)
-		goto out;
+	if (!devfreq->previous_freq) {
+		spin_lock(&devfreq->stats_lock);
+		devfreq->last_stat_updated = cur_time;
+		spin_unlock(&devfreq->stats_lock);
+		return 0;
+	}
 
 	prev_lev = devfreq_get_freq_level(devfreq, devfreq->previous_freq);
+
+	spin_lock(&devfreq->stats_lock);
 	if (prev_lev < 0) {
 		ret = prev_lev;
 		goto out;
@@ -174,7 +180,6 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
 
 	devfreq->time_in_state[prev_lev] +=
 			 cur_time - devfreq->last_stat_updated;
-
 	lev = devfreq_get_freq_level(devfreq, freq);
 	if (lev < 0) {
 		ret = lev;
@@ -189,6 +194,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
 
 out:
 	devfreq->last_stat_updated = cur_time;
+	spin_unlock(&devfreq->stats_lock);
 	return ret;
 }
 EXPORT_SYMBOL(devfreq_update_status);
@@ -478,7 +484,9 @@ void devfreq_monitor_resume(struct devfreq *devfreq)
 		queue_delayed_work(devfreq_wq, &devfreq->work,
 			msecs_to_jiffies(devfreq->profile->polling_ms));
 
+	spin_lock(&devfreq->stats_lock);
 	devfreq->last_stat_updated = get_jiffies_64();
+	spin_unlock(&devfreq->stats_lock);
 	devfreq->stop_polling = false;
 
 	if (devfreq->profile->get_cur_freq &&
@@ -707,6 +715,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 	}
 
 	devfreq->last_stat_updated = get_jiffies_64();
+	spin_lock_init(&devfreq->stats_lock);
 
 	srcu_init_notifier_head(&devfreq->transition_notifier_list);
 
@@ -1405,6 +1414,8 @@ static ssize_t trans_stat_show(struct device *dev,
 
 	len = sprintf(buf, "     From  :   To\n");
 	len += sprintf(buf + len, "           :");
+
+	spin_lock(&devfreq->stats_lock);
 	for (i = 0; i < max_state; i++)
 		len += sprintf(buf + len, "%10lu",
 				devfreq->profile->freq_table[i]);
@@ -1429,6 +1440,7 @@ static ssize_t trans_stat_show(struct device *dev,
 
 	len += sprintf(buf + len, "Total transition : %u\n",
 					devfreq->total_trans);
+	spin_unlock(&devfreq->stats_lock);
 	return len;
 }
 static DEVICE_ATTR_RO(trans_stat);
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index b81a86e47fb9..a344e0be99f3 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -135,6 +135,8 @@ struct devfreq_dev_profile {
  * @trans_table:	Statistics of devfreq transitions
  * @time_in_state:	Statistics of devfreq states
  * @last_stat_updated:	The last time stat updated
+ * @stats_lock:		Lock protecting trans_table, time_in_state, last_time
+ *			and total_trans used for statistics
  * @transition_notifier_list: list head of DEVFREQ_TRANSITION_NOTIFIER notifier
  *
  * This structure stores the devfreq information for a give device.
@@ -176,6 +178,7 @@ struct devfreq {
 	unsigned int *trans_table;
 	u64 *time_in_state;
 	unsigned long long last_stat_updated;
+	spinlock_t stats_lock;
 
 	struct srcu_notifier_head transition_notifier_list;
 };
-- 
2.24.0