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

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Date:   Tue, 24 Mar 2020 08:00:00 +0530
From:   Amit Kucheria <amit.kucheria@...durent.com>
To:     Daniel Lezcano <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>,
        "open list:THERMAL/CPU_COOLING" <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] thermal/drivers/cpufreq_cooling: Remove abusing WARN_ON

On Sun, Mar 22, 2020 at 1:01 AM Daniel Lezcano
<daniel.lezcano@...aro.org> wrote:
>
> 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>

Reviewed-by: Amit Kucheria <amit.kucheria@...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
>