From: Leonard Crestez leonard.crestez@nxp.com
commit 2abb0d5268ae7b5ddf82099b1f8d5aa8414637d4 upstream.
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@vger.kernel.org Signed-off-by: Leonard Crestez leonard.crestez@nxp.com Reviewed-by: Matthias Kaehlcke mka@chromium.org Reviewed-by: Chanwoo Choi cw00.choi@samsung.com Signed-off-by: Chanwoo Choi cw00.choi@samsung.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/devfreq/devfreq.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
--- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -163,6 +163,7 @@ int devfreq_update_status(struct devfreq 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. */ @@ -1287,12 +1288,17 @@ static ssize_t trans_stat_show(struct de 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++)