linux-kernel - [PATCH] thermal/drivers/cpufreq_cooling: Remove abusing WARN

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Date:   Sat, 21 Mar 2020 20:31:07 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     daniel.lezcano@...aro.org
Cc:     Amit Daniel Kachhap <amit.kachhap@...il.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Javi Merino <javi.merino@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        linux-pm@...r.kernel.org (open list:THERMAL/CPU_COOLING),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] thermal/drivers/cpufreq_cooling: Remove abusing WARN_ON

The WARN_ON macros are used at the entry functions state2power() and
set_cur_state().

state2power() is called with the max_state retrieved from
get_max_state which returns cpufreq_cdev->max_level, then it check if
max_state is > cpufreq_cdev->max_level. The test does not really makes
sense but let's assume we want to make sure to catch an error if the
code evolves. However the WARN_ON is overkill.

set_cur_state() is also called from userspace if we write to the
sysfs. It is easy to see a stack dumped by just writing to sysfs
/sys/class/thermal/cooling_device0/cur_state a value greater than
"max_level". A bit scary. Returing -EINVAL is enough.

Remove these WARN_ON.

Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
---
 drivers/thermal/cpufreq_cooling.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/cpufreq_cooling.c b/drivers/thermal/cpufreq_cooling.c
index af55ac08e1bd..d66791a71320 100644
--- a/drivers/thermal/cpufreq_cooling.c
+++ b/drivers/thermal/cpufreq_cooling.c
@@ -273,7 +273,7 @@ static int cpufreq_state2power(struct thermal_cooling_device *cdev,
 	struct cpufreq_cooling_device *cpufreq_cdev = cdev->devdata;
 
 	/* Request state should be less than max_level */
-	if (WARN_ON(state > cpufreq_cdev->max_level))
+	if (state > cpufreq_cdev->max_level)
 		return -EINVAL;
 
 	num_cpus = cpumask_weight(cpufreq_cdev->policy->cpus);
@@ -434,7 +434,7 @@ static int cpufreq_set_cur_state(struct thermal_cooling_device *cdev,
 	int ret;
 
 	/* Request state should be less than max_level */
-	if (WARN_ON(state > cpufreq_cdev->max_level))
+	if (state > cpufreq_cdev->max_level)
 		return -EINVAL;
 
 	/* Check if the old cooling action is same as new cooling action */
-- 
2.17.1