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 <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index b7f2963..283c08f 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -1332,9 +1332,15 @@
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 @@
/* 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
