linux-kernel - Re: drivers/acpi/processor_thermal.c: avoid cpufreq_get

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Date:   Thu, 30 Dec 2021 17:23:13 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Manfred Spraul <manfred@...orfullife.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>, Len Brown <lenb@...nel.org>,
        1vier1@....de
Subject: Re: drivers/acpi/processor_thermal.c: avoid cpufreq_get_policy()

On Wed, Dec 22, 2021 at 8:14 PM Manfred Spraul <manfred@...orfullife.com> wrote:
>
> cpu_has_cpufreq() stores a 'struct cpufreq_policy' on the stack.
> Unfortunately, with debugging options enabled, the structure can be
> larger than 1024 bytes, which causes a compiler warning/error.
>
> (actually observed: 1184 bytes).
>
> Therefore: Switch to cpufreq_cpu_get().
>
> Signed-off-by: Manfred Spraul <manfred@...orfullife.com>
>
> ---
>  drivers/acpi/processor_thermal.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/acpi/processor_thermal.c b/drivers/acpi/processor_thermal.c
> index a3d34e3f9f94..74210d63f62c 100644
> --- a/drivers/acpi/processor_thermal.c
> +++ b/drivers/acpi/processor_thermal.c
> @@ -53,10 +53,19 @@ static int phys_package_first_cpu(int cpu)
>
>  static int cpu_has_cpufreq(unsigned int cpu)
>  {
> -       struct cpufreq_policy policy;
> -       if (!acpi_processor_cpufreq_init || cpufreq_get_policy(&policy, cpu))
> +       struct cpufreq_policy *policy;
> +       int retval;

Why is this needed?

> +
> +       if (!acpi_processor_cpufreq_init)
>                 return 0;
> -       return 1;
> +
> +       retval = 0;
> +       policy = cpufreq_cpu_get(cpu);
> +       if (policy) {
> +               cpufreq_cpu_put(policy);

return 1;

> +               retval = 1;
> +       }
> +       return retval;

return 0;

>  }
>
>  static int cpufreq_get_max_state(unsigned int cpu)
> --
> 2.33.1
>