Message-ID: <52e322e5-2dd4-488c-a98e-3a4018f0c323@kylinos.cn>
Date: Thu, 4 Sep 2025 18:37:54 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Viresh Kumar <viresh.kumar@...aro.org>,
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Subject: Re: [PATCH v4 07/10] powercap: dtpm_cpu: Use scope-based cleanup
 helper


在 2025/9/3 21:45, Rafael J. Wysocki 写道:
> On Wed, Sep 3, 2025 at 3:18 PM Zihuan Zhang <zhangzihuan@...inos.cn> wrote:
>> Replace the manual cpufreq_cpu_put() with __free(put_cpufreq_policy)
>> annotation for policy references. This reduces the risk of reference
>> counting mistakes and aligns the code with the latest kernel style.
>>
>> No functional change intended.
>>
>> Signed-off-by: Zihuan Zhang <zhangzihuan@...inos.cn>
>> ---
>>   drivers/powercap/dtpm_cpu.c | 30 +++++++++++-------------------
>>   1 file changed, 11 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/powercap/dtpm_cpu.c b/drivers/powercap/dtpm_cpu.c
>> index 99390ec1481f..f76594185fa2 100644
>> --- a/drivers/powercap/dtpm_cpu.c
>> +++ b/drivers/powercap/dtpm_cpu.c
>> @@ -144,19 +144,17 @@ static int update_pd_power_uw(struct dtpm *dtpm)
>>   static void pd_release(struct dtpm *dtpm)
>>   {
>>          struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm);
>> -       struct cpufreq_policy *policy;
>>
>>          if (freq_qos_request_active(&dtpm_cpu->qos_req))
>>                  freq_qos_remove_request(&dtpm_cpu->qos_req);
>>
>> -       policy = cpufreq_cpu_get(dtpm_cpu->cpu);
>> -       if (policy) {
>> +       struct cpufreq_policy *policy __free(put_cpufreq_policy) =
>> +               cpufreq_cpu_get(dtpm_cpu->cpu);
>> +
>> +       if (policy)
>>                  for_each_cpu(dtpm_cpu->cpu, policy->related_cpus)
>>                          per_cpu(dtpm_per_cpu, dtpm_cpu->cpu) = NULL;
>>
>> -               cpufreq_cpu_put(policy);
>> -       }
>> -
>>          kfree(dtpm_cpu);
>>   }
>>
>> @@ -192,7 +190,6 @@ static int cpuhp_dtpm_cpu_online(unsigned int cpu)
>>   static int __dtpm_cpu_setup(int cpu, struct dtpm *parent)
>>   {
>>          struct dtpm_cpu *dtpm_cpu;
>> -       struct cpufreq_policy *policy;
>>          struct em_perf_state *table;
>>          struct em_perf_domain *pd;
>>          char name[CPUFREQ_NAME_LEN];
>> @@ -202,21 +199,19 @@ static int __dtpm_cpu_setup(int cpu, struct dtpm *parent)
>>          if (dtpm_cpu)
>>                  return 0;
>>
>> -       policy = cpufreq_cpu_get(cpu);
>> +       struct cpufreq_policy *policy __free(put_cpufreq_policy) =
>> +               cpufreq_cpu_get(cpu);
>> +
>>          if (!policy)
>>                  return 0;
>>
>>          pd = em_cpu_get(cpu);
>> -       if (!pd || em_is_artificial(pd)) {
>> -               ret = -EINVAL;
>> -               goto release_policy;
>> -       }
>> +       if (!pd || em_is_artificial(pd))
>> +               return -EINVAL;
>>
>>          dtpm_cpu = kzalloc(sizeof(*dtpm_cpu), GFP_KERNEL);
>> -       if (!dtpm_cpu) {
>> -               ret = -ENOMEM;
>> -               goto release_policy;
>> -       }
>> +       if (!dtpm_cpu)
>> +               return -ENOMEM;
>>
>>          dtpm_init(&dtpm_cpu->dtpm, &dtpm_ops);
>>          dtpm_cpu->cpu = cpu;
>> @@ -239,7 +234,6 @@ static int __dtpm_cpu_setup(int cpu, struct dtpm *parent)
>>          if (ret < 0)
>>                  goto out_dtpm_unregister;
> So this change kind of goes against another recommendation given in cleanup.h:
>
>   * Lastly, given that the benefit of cleanup helpers is removal of
>   * "goto", and that the "goto" statement can jump between scopes, the
>   * expectation is that usage of "goto" and cleanup helpers is never
>   * mixed in the same function. I.e. for a given routine, convert all
>   * resources that need a "goto" cleanup to scope-based cleanup, or
>   * convert none of them.


Should I replace all the memory allocation cleanups here with `__free`?
That would allow us to drop all the `goto`s, but since this function has
quite a few of them, I’m concerned it might introduce new issues. What’s
your recommendation?

Thanks!

>> -       cpufreq_cpu_put(policy);
>>          return 0;
>>
>>   out_dtpm_unregister:
>> @@ -251,8 +245,6 @@ static int __dtpm_cpu_setup(int cpu, struct dtpm *parent)
>>                  per_cpu(dtpm_per_cpu, cpu) = NULL;
>>          kfree(dtpm_cpu);
>>
>> -release_policy:
>> -       cpufreq_cpu_put(policy);
>>          return ret;
>>   }
>>
>> --

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