linux-kernel - Re: [PATCH v2 4/7] ACPI: processor: idle: Disable ACPI idle if get power information failed in power notify

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Message-ID: <CAJZ5v0idhxfOa8_Zp4Z_j5Rqh4GW4JsBpGT_hT=v=NgcEZRb+g@mail.gmail.com>
Date: Mon, 3 Nov 2025 19:09:14 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Huisong Li <lihuisong@...wei.com>
Cc: rafael@...nel.org, lenb@...nel.org, linux-acpi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Sudeep.Holla@....com, linuxarm@...wei.com, 
	jonathan.cameron@...wei.com, zhanjie9@...ilicon.com, zhenglifeng1@...wei.com, 
	yubowen8@...wei.com
Subject: Re: [PATCH v2 4/7] ACPI: processor: idle: Disable ACPI idle if get
 power information failed in power notify

On Mon, Nov 3, 2025 at 9:42 AM Huisong Li <lihuisong@...wei.com> wrote:
>
> The old states may not be usable any more if get power information
> failed in power notify. The ACPI idle should be disabled entirely.

How does it actually disable anything?  It only changes the
acpi_processor_power_state_has_changed() return value AFAICS, but that
return value isn't checked.

> Fixes: f427e5f1cf75 ("ACPI / processor: Get power info before updating the C-states")

So how does it fix anything?

> Signed-off-by: Huisong Li <lihuisong@...wei.com>
> ---
>  drivers/acpi/processor_idle.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index c73df5933691..4627b00257e6 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -1317,6 +1317,7 @@ int acpi_processor_power_state_has_changed(struct acpi_processor *pr)
>         int cpu;
>         struct acpi_processor *_pr;
>         struct cpuidle_device *dev;
> +       int ret = 0;
>
>         if (disabled_by_idle_boot_param())
>                 return 0;
> @@ -1345,8 +1346,18 @@ int acpi_processor_power_state_has_changed(struct acpi_processor *pr)
>                         cpuidle_disable_device(dev);
>                 }
>
> -               /* Populate Updated C-state information */
> -               acpi_processor_get_power_info(pr);
> +               /*
> +                * Populate Updated C-state information
> +                * The same idle state is used for all CPUs, cpuidle of all CPUs
> +                * should be disabled.
> +                */
> +               ret = acpi_processor_get_power_info(pr);
> +               if (ret) {
> +                       pr_err("Get processor-%u power information failed, disable cpuidle of all CPUs\n",
> +                              pr->id);

pr_info() at most, preferably pr_debug() or maybe pr_info_once().

> +                       goto release_lock;

"unlock" would be a better name.

> +               }
> +
>                 acpi_processor_setup_cpuidle_states(pr);
>
>                 /* Enable all cpuidle devices */
> @@ -1354,18 +1365,19 @@ int acpi_processor_power_state_has_changed(struct acpi_processor *pr)
>                         _pr = per_cpu(processors, cpu);
>                         if (!_pr || !_pr->flags.power_setup_done)
>                                 continue;
> -                       acpi_processor_get_power_info(_pr);
> -                       if (_pr->flags.power) {
> +                       ret = acpi_processor_get_power_info(_pr);

This does not need to be called if _pr->flags.power is unset.  Why are
you changing this?

> +                       if (!ret && _pr->flags.power) {
>                                 dev = per_cpu(acpi_cpuidle_device, cpu);
>                                 acpi_processor_setup_cpuidle_dev(_pr, dev);
>                                 cpuidle_enable_device(dev);
>                         }

If it succeeds for the next CPU, the return value will be still 0, won't it?

>                 }
> +release_lock:
>                 cpuidle_resume_and_unlock();
>                 cpus_read_unlock();
>         }
>
> -       return 0;
> +       return ret;
>  }
>
>  void acpi_processor_register_idle_driver(void)
> --