ACPI / cpuidle: fix deadlock between cpuidle_lock and cpu_hotplug.lock
There is a following AB-BA dependency between cpu_hotplug.lock and
cpuidle_lock:
1) cpu_hotplug.lock -> cpuidle_lock
enable_nonboot_cpus()
_cpu_up()
cpu_hotplug_being()
LOCK(cpu_hotplug.lock)
cpu_notify()
...
acpi_processor_hotplug()
cpuidle_pause_and_lock()
LOCK(cpuidle_lock)
2) cpuidle_lock -> cpu_hotplug.lock
acpi_os_execute_deferred() workqueue
...
acpi_processor_cst_has_changed()
cpuidle_pause_and_lock()
LOCK(cpuidle_lock)
get_online_cpus()
LOCK(cpu_hotplug.lock)
Fix this by reversing the order acpi_processor_cst_has_changed() does thigs --
let it first execute the protection against CPU hotplug by calling get_online_cpus()
and obtain the cpuidle lock only after that (and perform the symmentric change
when allowing CPUs hotplug again and dropping cpuidle lock).
Spotted by lockdep.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
1 file changed
