From: Leonard Crestez <leonard.crestez@nxp.com>
To: Matthias Kaehlcke <mka@chromium.org>,
MyungJoo Ham <myungjoo.ham@samsung.com>,
Kyungmin Park <kyungmin.park@samsung.com>
Cc: "Artur Świgoń" <a.swigon@partner.samsung.com>,
linux-pm@vger.kernel.org, "Krzysztof Kozlowski" <krzk@kernel.org>,
"Lukasz Luba" <l.luba@partner.samsung.com>,
"Chanwoo Choi" <cw00.choi@samsung.com>,
"NXP Linux Team" <linux-imx@nxp.com>,
"Georgi Djakov" <georgi.djakov@linaro.org>,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH] PM / devfreq: Lock devfreq in trans_stat_show
Date: Mon, 23 Sep 2019 19:27:27 +0300 [thread overview]
Message-ID: <714675448e7fbf3c930b0dca6fbe54fa5f87211b.1569256001.git.leonard.crestez@nxp.com> (raw)
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.
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
---
drivers/devfreq/devfreq.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
Changes since v1:
* Split from series: low-priority bugfix not strictly required for PM QoS
* Only keep lock during update, release before sprintf
Link to v1: https://patchwork.kernel.org/patch/11149493/
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 4c58fbf7d4e4..00fc23fea5b2 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -206,10 +206,11 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
{
int lev, prev_lev, ret = 0;
unsigned long cur_time;
cur_time = jiffies;
+ lockdep_assert_held(&devfreq->lock);
/* Immediately exit if previous_freq is not initialized yet. */
if (!devfreq->previous_freq)
goto out;
@@ -1507,16 +1508,22 @@ static ssize_t trans_stat_show(struct device *dev,
struct devfreq *devfreq = to_devfreq(dev);
ssize_t len;
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");
+ /* lock and update */
+ 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++)
len += sprintf(buf + len, "%10lu",
devfreq->profile->freq_table[i]);
--
2.17.1
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next reply other threads:[~2019-09-23 16:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20190923162736epcas3p2c1db3bf767a07f17b609bc91fbbd9648@epcas3p2.samsung.com>
2019-09-23 16:27 ` Leonard Crestez [this message]
2019-09-23 18:54 ` [PATCH] PM / devfreq: Lock devfreq in trans_stat_show Matthias Kaehlcke
2019-09-23 23:34 ` Matthias Kaehlcke
2019-09-24 2:11 ` Chanwoo Choi
2019-09-24 7:44 ` Leonard Crestez
2019-09-24 15:44 ` Matthias Kaehlcke
2019-09-25 1:21 ` Chanwoo Choi
2019-09-25 19:36 ` Leonard Crestez
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