Re: [PATCH v1 1/4] ACPI: processor: Reorder acpi_processor_driver_init()

["Zhang, Rui" <rui.zhang@intel.com>]

On Fri, 2023-03-03 at 20:19 +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.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.
> 
> Fixes: a365105c685c("thermal: sysfs: Reuse cdev->max_state")
> Reported-by: Wang, Quanxian <quanxian.wang@intel.com>
> Link: 
> https://lore.kernel.org/linux-pm/53ec1f06f61c984100868926f282647e57ecfb2d.camel@intel.com/
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

The full patch series fixes the problem but this one does not.

This is because,

static int cpu_has_cpufreq(unsigned int cpu)
{
        struct
cpufreq_policy *policy;

        if (!acpi_processor_cpufreq_init)
                return 0;

        policy = cpufreq_cpu_get(cpu);
        if (policy) {
                cpufreq_cpu_put(policy);
                return 1;
        }
        return 0;
}

Although acpi_processor_cpufreq_init is set to true with patch 1/4, but
we don't have cpufreq driver registered, thus cpufreq_cpu_get() return
NULL.

so acpi_processor_cpufreq_init is not the only dependency here. :(

thanks,
rui

> ---
>  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:
> 
> 
>