| From | Ben Hutchings <> | Date | Sat, 01 Nov 2014 22:28:03 +0000 | Subject | [PATCH 3.2 024/102] ACPI / cpuidle: fix deadlock between cpuidle_lock and cpu_hotplug.lock |
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3.2.64-rc1 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: Ben Hutchings <ben@decadent.org.uk> --- drivers/acpi/processor_idle.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -1165,9 +1165,9 @@ int acpi_processor_cst_has_changed(struc if (smp_processor_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) { @@ -1192,8 +1192,8 @@ int acpi_processor_cst_has_changed(struc cpuidle_enable_device(&_pr->power.dev); } } - put_online_cpus(); cpuidle_resume_and_unlock(); + put_online_cpus(); } return 0;
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