The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 2abb0d5268ae7b5ddf82099b1f8d5aa8414637d4 Mon Sep 17 00:00:00 2001
From: Leonard Crestez <leonard.crestez@xxxxxxx>
Date: Tue, 24 Sep 2019 10:52:23 +0300
Subject: [PATCH] PM / devfreq: Lock devfreq in trans_stat_show
There is no locking in this sysfs show function so stats printing can
race with a devfreq_update_status called as part of freq switching or
with initialization.
Also add an assert in devfreq_update_status to make it clear that lock
must be held by caller.
Fixes: 39688ce6facd ("PM / devfreq: account suspend/resume for stats")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Leonard Crestez <leonard.crestez@xxxxxxx>
Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Reviewed-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
Signed-off-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 60859a2400bc..d6c3dce9e9d5 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -160,6 +160,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
int lev, prev_lev, ret = 0;
unsigned long cur_time;
+ lockdep_assert_held(&devfreq->lock);
cur_time = jiffies;
/* Immediately exit if previous_freq is not initialized yet. */
@@ -1397,12 +1398,17 @@ static ssize_t trans_stat_show(struct device *dev,
int i, j;
unsigned int max_state = devfreq->profile->max_state;
- if (!devfreq->stop_polling &&
- devfreq_update_status(devfreq, devfreq->previous_freq))
- return 0;
if (max_state == 0)
return sprintf(buf, "Not Supported.\n");
+ mutex_lock(&devfreq->lock);
+ if (!devfreq->stop_polling &&
+ devfreq_update_status(devfreq, devfreq->previous_freq)) {
+ mutex_unlock(&devfreq->lock);
+ return 0;
+ }
+ mutex_unlock(&devfreq->lock);
+
len = sprintf(buf, " From : To\n");
len += sprintf(buf + len, " :");
for (i = 0; i < max_state; i++)
