From 43ff36c4a5a574ee83b4b0d3f3d74f09a3a8c2d3 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 25 Nov 2025 15:06:12 +0100 Subject: [PATCH] Revert "ACPI: processor: idle: Optimize ACPI idle driver registration" Revert commit 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle driver registration") because it is reported to introduce a cpuidle regression leading to a kernel crash on a platform using the ACPI idle driver. Signed-off-by: Rafael J. Wysocki Reported-by: Borislav Petkov Tested-by: Borislav Petkov (AMD) Closes: https://lore.kernel.org/lkml/20251124200019.GIaSS5U9HhsWBotrQZ@fat_crate.local/ --- drivers/acpi/processor_driver.c | 3 -- drivers/acpi/processor_idle.c | 65 ++++++++++++--------------------- include/acpi/processor.h | 2 - 3 files changed, 23 insertions(+), 47 deletions(-) diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c index de17c14126780..7644de24d2faa 100644 --- a/drivers/acpi/processor_driver.c +++ b/drivers/acpi/processor_driver.c @@ -263,8 +263,6 @@ static int __init acpi_processor_driver_init(void) if (result < 0) return result; - acpi_processor_register_idle_driver(); - result = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "acpi/cpu-drv:online", acpi_soft_cpu_online, NULL); @@ -303,7 +301,6 @@ static void __exit acpi_processor_driver_exit(void) cpuhp_remove_state_nocalls(hp_online); cpuhp_remove_state_nocalls(CPUHP_ACPI_CPUDRV_DEAD); - acpi_processor_unregister_idle_driver(); driver_unregister(&acpi_processor_driver); } diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 5dacf41d7cc0a..4166090db6420 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -1357,48 +1357,7 @@ int acpi_processor_power_state_has_changed(struct acpi_processor *pr) return 0; } -void acpi_processor_register_idle_driver(void) -{ - struct acpi_processor *pr; - int ret = -ENODEV; - int cpu; - - /* - * Acpi idle driver is used by all possible CPUs. - * Install the idle handler by the processor power info of one in them. - * Note that we use previously set idle handler will be used on - * platforms that only support C1. - */ - for_each_cpu(cpu, (struct cpumask *)cpu_possible_mask) { - pr = per_cpu(processors, cpu); - if (!pr) - continue; - - ret = acpi_processor_get_power_info(pr); - if (!ret) { - pr->flags.power_setup_done = 1; - acpi_processor_setup_cpuidle_states(pr); - break; - } - } - - if (ret) { - pr_debug("No ACPI power information from any CPUs.\n"); - return; - } - - ret = cpuidle_register_driver(&acpi_idle_driver); - if (ret) { - pr_debug("register %s failed.\n", acpi_idle_driver.name); - return; - } - pr_debug("%s registered with cpuidle.\n", acpi_idle_driver.name); -} - -void acpi_processor_unregister_idle_driver(void) -{ - cpuidle_unregister_driver(&acpi_idle_driver); -} +static int acpi_processor_registered; int acpi_processor_power_init(struct acpi_processor *pr) { @@ -1413,7 +1372,22 @@ int acpi_processor_power_init(struct acpi_processor *pr) if (!acpi_processor_get_power_info(pr)) pr->flags.power_setup_done = 1; + /* + * Install the idle handler if processor power management is supported. + * Note that we use previously set idle handler will be used on + * platforms that only support C1. + */ if (pr->flags.power) { + /* Register acpi_idle_driver if not already registered */ + if (!acpi_processor_registered) { + acpi_processor_setup_cpuidle_states(pr); + retval = cpuidle_register_driver(&acpi_idle_driver); + if (retval) + return retval; + pr_debug("%s registered with cpuidle\n", + acpi_idle_driver.name); + } + dev = kzalloc(sizeof(*dev), GFP_KERNEL); if (!dev) return -ENOMEM; @@ -1426,11 +1400,14 @@ int acpi_processor_power_init(struct acpi_processor *pr) */ retval = cpuidle_register_device(dev); if (retval) { + if (acpi_processor_registered == 0) + cpuidle_unregister_driver(&acpi_idle_driver); per_cpu(acpi_cpuidle_device, pr->id) = NULL; kfree(dev); return retval; } + acpi_processor_registered++; } return 0; } @@ -1444,6 +1421,10 @@ int acpi_processor_power_exit(struct acpi_processor *pr) if (pr->flags.power) { cpuidle_unregister_device(dev); + acpi_processor_registered--; + if (acpi_processor_registered == 0) + cpuidle_unregister_driver(&acpi_idle_driver); + kfree(dev); } diff --git a/include/acpi/processor.h b/include/acpi/processor.h index ff864c1cee3a4..d0eccbd920e5c 100644 --- a/include/acpi/processor.h +++ b/include/acpi/processor.h @@ -423,8 +423,6 @@ int acpi_processor_power_init(struct acpi_processor *pr); int 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); -void acpi_processor_unregister_idle_driver(void); #else static inline int acpi_processor_power_init(struct acpi_processor *pr) { -- 2.47.3