Re: [PATCH v4 07/10] powercap: dtpm_cpu: Use scope-based cleanup helper

["Rafael J. Wysocki" <rafael@kernel.org>]

On Wed, Sep 3, 2025 at 3:18 PM Zihuan Zhang <zhangzihuan@kylinos.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@kylinos.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.

>
> -       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;
>  }
>
> --