Commit b032bf70 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
Browse files

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

Based on a debug patch from Ingo Molnar
Signed-off-by: default avatarThomas Gleixner <>
Signed-off-by: default avatarLinus Torvalds <>
parent 9ffc1699
......@@ -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. */
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
......@@ -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;
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