linux-kernel - Re: [PATCH] cpufreq: exit() callback is optional

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Date: Fri, 12 Apr 2024 13:08:21 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, linux-pm@...r.kernel.org, 
	Vincent Guittot <vincent.guittot@...aro.org>, sensor1010@....com, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: exit() callback is optional

On Fri, Apr 12, 2024 at 7:49 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> The exit() callback is optional and shouldn't be called without checking
> a valid pointer first.
>
> Also, we must clear freq_table pointer even if the exit() callback isn't
> present.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/cpufreq/cpufreq.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 66e10a19d76a..fd9c3ed21f49 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1679,10 +1679,13 @@ static void __cpufreq_offline(unsigned int cpu, struct cpufreq_policy *policy)
>          */
>         if (cpufreq_driver->offline) {
>                 cpufreq_driver->offline(policy);
> -       } else if (cpufreq_driver->exit) {
> -               cpufreq_driver->exit(policy);
> -               policy->freq_table = NULL;
> +               return;
>         }
> +
> +       if (cpufreq_driver->exit)
> +               cpufreq_driver->exit(policy);
> +
> +       policy->freq_table = NULL;
>  }
>
>  static int cpufreq_offline(unsigned int cpu)
> @@ -1740,7 +1743,7 @@ static void cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif)
>         }
>
>         /* We did light-weight exit earlier, do full tear down now */
> -       if (cpufreq_driver->offline)
> +       if (cpufreq_driver->offline && cpufreq_driver->exit)
>                 cpufreq_driver->exit(policy);
>
>         up_write(&policy->rwsem);
> --

I have applied this patch (for 6.10 because I don't think it is
urgent) because it addresses both issues with missing ->exit() driver
callback checks.  I honestly don't think it would be better to apply a
separate patch for each of them.

Thanks!