From b032bf70df2e43149ce2b4e9a865b076c6140753 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 27 Jul 2008 23:47:12 +0200 Subject: [PATCH] ACPI/CPUIDLE: prevent setting pm_idle to NULL pm_idle_save resp. pm_idle_old can be NULL when the restore code in acpi_processor_cst_has_changed() resp. cpuidle_uninstall_idle_handler() is called. This can set pm_idle unconditinally to NULL, which causes the kernel to panic when calling pm_idle in the x86 idle code. This was covered by an extra check for !pm_idle in the x86 idle code, which was removed during the x86 idle code refactoring. Instead of restoring the pm_idle check in the x86 code prevent the acpi/cpuidle code to set pm_idle to NULL. Reported by: Dhaval Giani http://lkml.org/lkml/2008/7/2/309 Based on a debug patch from Ingo Molnar Signed-off-by: Thomas Gleixner Signed-off-by: Linus Torvalds --- drivers/acpi/processor_idle.c | 15 +++++++++++---- drivers/cpuidle/cpuidle.c | 2 +- 2 files changed, 12 insertions(+), 5 deletions(-) diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index b7f2963693a7..283c08f5f4d4 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -1332,9 +1332,15 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr) if (!pr->flags.power_setup_done) return -ENODEV; - /* Fall back to the default idle loop */ - pm_idle = pm_idle_save; - synchronize_sched(); /* Relies on interrupts forcing exit from idle. */ + /* + * Fall back to the default idle loop, when pm_idle_save had + * been initialized. + */ + if (pm_idle_save) { + pm_idle = pm_idle_save; + /* Relies on interrupts forcing exit from idle. */ + synchronize_sched(); + } pr->flags.power = 0; result = acpi_processor_get_power_info(pr); @@ -1896,7 +1902,8 @@ int acpi_processor_power_exit(struct acpi_processor *pr, /* Unregister the idle handler when processor #0 is removed. */ if (pr->id == 0) { - pm_idle = pm_idle_save; + if (pm_idle_save) + pm_idle = pm_idle_save; /* * We are about to unload the current idle thread pm callback diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 5405769020a1..5ce07b517c58 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -94,7 +94,7 @@ void cpuidle_install_idle_handler(void) */ void cpuidle_uninstall_idle_handler(void) { - if (enabled_devices && (pm_idle != pm_idle_old)) { + if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) { pm_idle = pm_idle_old; cpuidle_kick_cpus(); }