linux-kernel - Re: [PATCH v2 1/4] ACPI: processor: Reorder acpi_processor_driver

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Date:   Tue, 14 Mar 2023 02:03:01 +0000
From:   "Zhang, Rui" <rui.zhang@...el.com>
To:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>
CC:     "srinivas.pandruvada@...ux.intel.com" 
        <srinivas.pandruvada@...ux.intel.com>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "Wang, Quanxian" <quanxian.wang@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] ACPI: processor: Reorder
 acpi_processor_driver_init()

On Mon, 2023-03-13 at 15:27 +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The cpufreq policy notifier in the ACPI processor driver may as
> well be registered before the driver itself, which causes
> acpi_processor_cpufreq_init to be true (unless the notifier
> registration fails, which is unlikely at that point) when the
> ACPI CPU thermal cooling devices are registered, so the
> processor_get_max_state() result does not change while
> acpi_processor_driver_init() is running.
> 
> Change the ordering in acpi_processor_driver_init() accordingly
> to prevent the max_state value from remaining 0 permanently for all
> ACPI CPU cooling devices due to setting acpi_processor_cpufreq_init
> too late.  [Note that processor_get_max_state() may still return
> different values at different times after this change, depending on
> the cpufreq driver registration time, but that issue needs to be
> addressed separately.]
> 
> Fixes: a365105c685c("thermal: sysfs: Reuse cdev->max_state")
> Reported-by: Wang, Quanxian <quanxian.wang@...el.com>
> Link: 
> https://lore.kernel.org/linux-pm/53ec1f06f61c984100868926f282647e57ecfb2d.camel@intel.com/
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Tested-by: Zhang Rui <rui.zhang@...el.com>
Reviewed-by: Zhang Rui <rui.zhang@...el.com>

thanks,
rui
> ---
> 
> v1 -> v2: Expand changelog to explain that this particular patch
> addresses
>           part of the issue.
> 
> ---
>  drivers/acpi/processor_driver.c |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> Index: linux-pm/drivers/acpi/processor_driver.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/processor_driver.c
> +++ linux-pm/drivers/acpi/processor_driver.c
> @@ -263,6 +263,12 @@ static int __init acpi_processor_driver_
>  	if (acpi_disabled)
>  		return 0;
>  
> +	if (!cpufreq_register_notifier(&acpi_processor_notifier_block,
> +				       CPUFREQ_POLICY_NOTIFIER)) {
> +		acpi_processor_cpufreq_init = true;
> +		acpi_processor_ignore_ppc_init();
> +	}
> +
>  	result = driver_register(&acpi_processor_driver);
>  	if (result < 0)
>  		return result;
> @@ -276,12 +282,6 @@ static int __init acpi_processor_driver_
>  	cpuhp_setup_state_nocalls(CPUHP_ACPI_CPUDRV_DEAD, "acpi/cpu-
> drv:dead",
>  				  NULL, acpi_soft_cpu_dead);
>  
> -	if (!cpufreq_register_notifier(&acpi_processor_notifier_block,
> -				       CPUFREQ_POLICY_NOTIFIER)) {
> -		acpi_processor_cpufreq_init = true;
> -		acpi_processor_ignore_ppc_init();
> -	}
> -
>  	acpi_processor_throttling_init();
>  	return 0;
>  err:
> 
> 
>