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

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Date:   Thu, 30 Dec 2021 17:47:32 +0100
From:   Manfred Spraul <manfred@...orfullife.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.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()

Hi Rafael,

On 12/30/21 17:23, Rafael J. Wysocki wrote:
> 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?
You are right, this can be simplified. Updated patch is attached.
>> +
>> +       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
>>

View attachment "0001-drivers-acpi-processor_thermal.c-avoid-cpufreq_get_p.patch" of type "text/x-patch" (1363 bytes)