From: Jiri Kosina Date: Wed, 3 Sep 2014 13:04:28 +0000 (+0200) Subject: ACPI / cpuidle: fix deadlock between cpuidle_lock and cpu_hotplug.lock X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=4f6a1e6210f5aeed2832d69103fc6511c0ca7c2d;p=linux-edison.git ACPI / cpuidle: fix deadlock between cpuidle_lock and cpu_hotplug.lock 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 Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index 4056d317517..a88894190e4 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -1101,9 +1101,9 @@ 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) { @@ -1130,8 +1130,8 @@ 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;