Re: [PATCH] ACPI: processor: Add cpuidle driver check in acpi_processor_register_idle_driver

[lihuisong (C)]

Hello Tony,

Thank you for reporting this issue. Good point.
This patch is messy and not good to review and merge. please resend it.
In addition, suggest you add a fixed tag.

/Huisong


On 5/19/2026 5:19 PM, Tony W Wang-oc wrote:
> Commit 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idledriver registration") moved the ACPI idle driver registration toacpi_processor_driver_init(), but it didn't check whether a cpuidledriver was already registered.For example, on Intel platforms, if the intel_idle driver is alreadyloaded, the code would still evaluate the _CST object in the ACPItable and attempt to register the acpi_idle driver. This registrationwould fail with -EBUSY due to the existing check in cpuidle_register_driver.Add a check at the beginning of acpi_processor_register_idle_driver()to avoid unnecessary _CST evaluate and potential registration failures.--- drivers/acpi/processor_idle.c | 5 +++++ 1 file changed, 5 insertions(+)diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.cindex ee5facccbe10..0409411abb83 100644--- a/drivers/acpi/processor_idle.c+++ b/drivers/acpi/processor_idle.c@@ -1355,6 +1355,11 @@ void acpi_processor_register_idle_driver(void) 	int ret = -ENODEV; 	int cpu; +	if (cpuidle_get_driver()) {+		pr_debug("cpuidle driver %pS already registered.\n", cpuidle_get_driver());+		return;+	}+ 	acpi_processor_update_max_cstate();  	/*-- 2.25.1
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