2023-03-13 14:35:01

by Rafael J. Wysocki

Subject: [PATCH v2 1/4] ACPI: processor: Reorder acpi_processor_driver_init()

From: Rafael J. Wysocki <[email protected]>

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 <[email protected]>
Link: https://lore.kernel.org/linux-pm/[email protected]/
Signed-off-by: Rafael J. Wysocki <[email protected]>
---

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:

2023-03-14 02:03:22

by Zhang, Rui

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 <[email protected]>
>
> 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 <[email protected]>
> Link:
> https://lore.kernel.org/linux-pm/[email protected]/
> Signed-off-by: Rafael J. Wysocki <[email protected]>

Tested-by: Zhang Rui <[email protected]>
Reviewed-by: Zhang Rui <[email protected]>

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:
>
>
>