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Date: Mon, 15 Sep 2014 12:26:09 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Jiri Kosina <jkosina@...e.cz>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com> Subject: [PATCH 3.14 069/114] ACPI / cpuidle: fix deadlock between cpuidle_lock and cpu_hotplug.lock 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiri Kosina <jkosina@...e.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@...e.cz> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- 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 @@ -1071,9 +1071,9 @@ int acpi_processor_cst_has_changed(struc 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(struc cpuidle_enable_device(dev); } } - put_online_cpus(); cpuidle_resume_and_unlock(); + put_online_cpus(); } return 0; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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