[PATCH v1 0/2] ACPI: processor: idle: Fix and cleanup

[PATCH v1 0/2] ACPI: processor: idle: Fix and cleanup

[Rafael J. Wysocki]

Hi All,

One of the recent changes forgot to update a cpuidle driver check in the
ACPI processor driver, so fix this (first patch).

In addition, redefine two functions whose return values are ignored as
void (second patch).

Thanks!

[PATCH v1 1/2] ACPI: processor: Update cpuidle driver check in __acpi_processor_start()

[Rafael J. Wysocki]

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);

Re: [PATCH v1 1/2] ACPI: processor: Update cpuidle driver check in __acpi_processor_start()

[Rafael J. Wysocki]

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);
>
>
>
>

Re: [PATCH v1 1/2] ACPI: processor: Update cpuidle driver check in __acpi_processor_start()

[lihuisong (C)]

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);
>>
>>
>>
>>

[PATCH v1 2/2] ACPI: processor: idle: Redefine two functions as void

[Rafael J. Wysocki]

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

Notice that acpi_processor_power_init() and acpi_processor_power_exit()
don't need to return any values because their callers don't check them
anyway, so redefine those functions as void.

While at it, rearrange the code in acpi_processor_power_init() to
reduce the indentation level, get rid of a redundant local variable
in that function, and rephrase a code comment in it.

No intentional functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/processor_idle.c |   47 +++++++++++++++++++-----------------------
 include/acpi/processor.h      |    4 +--
 2 files changed, 24 insertions(+), 27 deletions(-)

--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -1137,47 +1137,45 @@ void acpi_processor_unregister_idle_driv
 	cpuidle_unregister_driver(&acpi_idle_driver);
 }
 
-int acpi_processor_power_init(struct acpi_processor *pr)
+void acpi_processor_power_init(struct acpi_processor *pr)
 {
-	int retval;
 	struct cpuidle_device *dev;
 
 	if (disabled_by_idle_boot_param())
-		return 0;
+		return;
 
 	acpi_processor_cstate_first_run_checks();
 
 	if (!acpi_processor_get_power_info(pr))
 		pr->flags.power_setup_done = 1;
 
-	if (pr->flags.power) {
-		dev = kzalloc(sizeof(*dev), GFP_KERNEL);
-		if (!dev)
-			return -ENOMEM;
-		per_cpu(acpi_cpuidle_device, pr->id) = dev;
-
-		acpi_processor_setup_cpuidle_dev(pr, dev);
-
-		/* Register per-cpu cpuidle_device. Cpuidle driver
-		 * must already be registered before registering device
-		 */
-		retval = cpuidle_register_device(dev);
-		if (retval) {
-
-			per_cpu(acpi_cpuidle_device, pr->id) = NULL;
-			kfree(dev);
-			return retval;
-		}
+	if (!pr->flags.power)
+		return;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return;
+
+	per_cpu(acpi_cpuidle_device, pr->id) = dev;
+
+	acpi_processor_setup_cpuidle_dev(pr, dev);
+
+	/*
+	 * Register a cpuidle device for this CPU.  The cpuidle driver using
+	 * this device is expected to be registered.
+	 */
+	if (cpuidle_register_device(dev)) {
+		per_cpu(acpi_cpuidle_device, pr->id) = NULL;
+		kfree(dev);
 	}
-	return 0;
 }
 
-int acpi_processor_power_exit(struct acpi_processor *pr)
+void acpi_processor_power_exit(struct acpi_processor *pr)
 {
 	struct cpuidle_device *dev = per_cpu(acpi_cpuidle_device, pr->id);
 
 	if (disabled_by_idle_boot_param())
-		return 0;
+		return;
 
 	if (pr->flags.power) {
 		cpuidle_unregister_device(dev);
@@ -1185,7 +1183,6 @@ int acpi_processor_power_exit(struct acp
 	}
 
 	pr->flags.power_setup_done = 0;
-	return 0;
 }
 
 MODULE_IMPORT_NS("ACPI_PROCESSOR_IDLE");
--- a/include/acpi/processor.h
+++ b/include/acpi/processor.h
@@ -419,8 +419,8 @@ static inline void acpi_processor_thrott
 /* in processor_idle.c */
 extern struct cpuidle_driver acpi_idle_driver;
 #ifdef CONFIG_ACPI_PROCESSOR_IDLE
-int acpi_processor_power_init(struct acpi_processor *pr);
-int acpi_processor_power_exit(struct acpi_processor *pr);
+void acpi_processor_power_init(struct acpi_processor *pr);
+void acpi_processor_power_exit(struct acpi_processor *pr);
 int acpi_processor_power_state_has_changed(struct acpi_processor *pr);
 int acpi_processor_hotplug(struct acpi_processor *pr);
 void acpi_processor_register_idle_driver(void);

Re: [PATCH v1 2/2] ACPI: processor: idle: Redefine two functions as void

[lihuisong (C)]

在 2025/9/19 5:10, Rafael J. Wysocki 写道:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Notice that acpi_processor_power_init() and acpi_processor_power_exit()
> don't need to return any values because their callers don't check them
> anyway, so redefine those functions as void.
>
> While at it, rearrange the code in acpi_processor_power_init() to
> reduce the indentation level, get rid of a redundant local variable
> in that function, and rephrase a code comment in it.
>
> No intentional functional impact.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
LGTM,
Acked-by: lihuisong@huawei.com
>
>
>

Re: [PATCH v1 0/2] ACPI: processor: idle: Fix and cleanup

[Mario Limonciello (AMD) (kernel.org)]

On 9/18/2025 4:07 PM, Rafael J. Wysocki wrote:
> Hi All,
> 
> One of the recent changes forgot to update a cpuidle driver check in the
> ACPI processor driver, so fix this (first patch).
> 
> In addition, redefine two functions whose return values are ignored as
> void (second patch).
> 
> Thanks!
> 
> 
> 

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>