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ACPI / cpuidle: fix deadlock between cpuidle_lock and cpu_hotplug.lock

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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_begin()
   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>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Jiri Kosina 2014-09-03 15:04:28 +02:00 committed by Rafael J. Wysocki
parent 69e273c0b0
commit 6726655dfd
1 changed files with 2 additions and 2 deletions
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4
drivers/acpi/processor_idle.c
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@ -1071,9 +1071,9 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr)
if (pr->id == 0 && cpuidle_get_driver() == &acpi_idle_driver) {
cpuidle_pause_and_lock();
/* Protect against cpu-hotplug */
get_online_cpus();
cpuidle_pause_and_lock();
/* Disable all cpuidle devices */
for_each_online_cpu(cpu) {
@ -1100,8 +1100,8 @@ int acpi_processor_cst_has_changed(struct acpi_processor *pr)
cpuidle_enable_device(dev);
}
}
put_online_cpus();
cpuidle_resume_and_unlock();
put_online_cpus();
}
return 0;