From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Commit 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle
driver registration") moved the ACPI idle driver registration to
acpi_processor_driver_init() and acpi_processor_power_init() does
not register an idle driver any more, so the cpuidle driver check
in __acpi_processor_start() needs to be updated to avoid calling
acpi_processor_power_init() without a cpuidle driver (in which
case the registration of the cpuidle device in that function
would fail anyway).

Fixes: 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle driver registration")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

Commit 7a8c994cbb2d is only in linux-next at this point.

---
 drivers/acpi/processor_driver.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -166,7 +166,7 @@ static int __acpi_processor_start(struct
 	if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
 		dev_dbg(&device->dev, "CPPC data invalid or not present\n");
 
-	if (!cpuidle_get_driver() || cpuidle_get_driver() == &acpi_idle_driver)
+	if (cpuidle_get_driver() == &acpi_idle_driver)
 		acpi_processor_power_init(pr);
 
 	acpi_pss_perf_init(pr);

On Thu, Sep 18, 2025 at 11:10 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Commit 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle
> driver registration") moved the ACPI idle driver registration to
> acpi_processor_driver_init() and acpi_processor_power_init() does
> not register an idle driver any more, so the cpuidle driver check
> in __acpi_processor_start() needs to be updated to avoid calling
> acpi_processor_power_init() without a cpuidle driver (in which
> case the registration of the cpuidle device in that function
> would fail anyway).

It's worse, it won't just fail, it'll lead to a NULL pointer
dereference in __cpuidle_register_device().

I'll update the changelog while applying the patch.


> Fixes: 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle driver registration")
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
>
> Commit 7a8c994cbb2d is only in linux-next at this point.
>
> ---
>  drivers/acpi/processor_driver.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/drivers/acpi/processor_driver.c
> +++ b/drivers/acpi/processor_driver.c
> @@ -166,7 +166,7 @@ static int __acpi_processor_start(struct
>         if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
>                 dev_dbg(&device->dev, "CPPC data invalid or not present\n");
>
> -       if (!cpuidle_get_driver() || cpuidle_get_driver() == &acpi_idle_driver)
> +       if (cpuidle_get_driver() == &acpi_idle_driver)
>                 acpi_processor_power_init(pr);
>
>         acpi_pss_perf_init(pr);
>
>
>
>

在 2025/9/19 19:17, Rafael J. Wysocki 写道:
> On Thu, Sep 18, 2025 at 11:10 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>>
>> Commit 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle
>> driver registration") moved the ACPI idle driver registration to
>> acpi_processor_driver_init() and acpi_processor_power_init() does
>> not register an idle driver any more, so the cpuidle driver check
>> in __acpi_processor_start() needs to be updated to avoid calling
>> acpi_processor_power_init() without a cpuidle driver (in which
>> case the registration of the cpuidle device in that function
>> would fail anyway).
> It's worse, it won't just fail, it'll lead to a NULL pointer
> dereference in __cpuidle_register_device().
>
> I'll update the changelog while applying the patch.
Yeah, thanks for fixing it.
Acked-by: lihuisong@huawei.com
>
>> Fixes: 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle driver registration")
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> ---
>>
>> Commit 7a8c994cbb2d is only in linux-next at this point.
>>
>> ---
>>   drivers/acpi/processor_driver.c |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> --- a/drivers/acpi/processor_driver.c
>> +++ b/drivers/acpi/processor_driver.c
>> @@ -166,7 +166,7 @@ static int __acpi_processor_start(struct
>>          if (result && !IS_ENABLED(CONFIG_ACPI_CPU_FREQ_PSS))
>>                  dev_dbg(&device->dev, "CPPC data invalid or not present\n");
>>
>> -       if (!cpuidle_get_driver() || cpuidle_get_driver() == &acpi_idle_driver)
>> +       if (cpuidle_get_driver() == &acpi_idle_driver)
>>                  acpi_processor_power_init(pr);
>>
>>          acpi_pss_perf_init(pr);
>>
>>
>>
>>