From 07494d547e92bde6857522d2a92ff70896aecadb Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:10:30 +0530 Subject: intel-idle: Fix CPU hotplug callback registration Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the intel-idle code by using this latter form of callback registration. Cc: Len Brown Cc: Ingo Molnar Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki --- drivers/idle/intel_idle.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'drivers/idle') diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index 8e1939f564f4..51493ed4643b 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -681,14 +681,19 @@ static int __init intel_idle_init(void) if (intel_idle_cpuidle_devices == NULL) return -ENOMEM; + cpu_notifier_register_begin(); + for_each_online_cpu(i) { retval = intel_idle_cpu_init(i); if (retval) { + cpu_notifier_register_done(); cpuidle_unregister_driver(&intel_idle_driver); return retval; } } - register_cpu_notifier(&cpu_hotplug_notifier); + __register_cpu_notifier(&cpu_hotplug_notifier); + + cpu_notifier_register_done(); return 0; } @@ -698,10 +703,13 @@ static void __exit intel_idle_exit(void) intel_idle_cpuidle_devices_uninit(); cpuidle_unregister_driver(&intel_idle_driver); + cpu_notifier_register_begin(); if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE) on_each_cpu(__setup_broadcast_timer, (void *)false, 1); - unregister_cpu_notifier(&cpu_hotplug_notifier); + __unregister_cpu_notifier(&cpu_hotplug_notifier); + + cpu_notifier_register_done(); return; } -- cgit v1.2.1