| From | Kamal Mostafa <> | Subject | [PATCH 3.13 103/103] ACPI / cpuidle: fix deadlock between cpuidle_lock and cpu_hotplug.lock | Date | Tue, 30 Sep 2014 14:31:48 -0700 |
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3.13.11.8 -stable review patch. If anyone has any objections, please let me know.
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From: Jiri Kosina <jkosina@suse.cz>
commit 6726655dfdd2dc60c035c690d9f10cb69d7ea075 upstream.
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> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- drivers/acpi/processor_idle.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 644516d..ba60290 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -1089,9 +1089,9 @@ 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) { @@ -1118,8 +1118,8 @@ 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; -- 1.9.1
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