From 82a8f131aadf55ac7fbc8c6f65f34d83101160de Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:07:04 +0530 Subject: [PATCH] x86, mce: 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 mce code in x86 by using this latter form of callback registration. Cc: Tony Luck Cc: Borislav Petkov Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki --- arch/x86/kernel/cpu/mcheck/mce.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 4d5419b249da..9b7734b1f975 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -2434,14 +2434,18 @@ static __init int mcheck_init_device(void) if (err) return err; + cpu_notifier_register_begin(); for_each_online_cpu(i) { err = mce_device_create(i); - if (err) + if (err) { + cpu_notifier_register_done(); return err; + } } register_syscore_ops(&mce_syscore_ops); - register_hotcpu_notifier(&mce_cpu_notifier); + __register_hotcpu_notifier(&mce_cpu_notifier); + cpu_notifier_register_done(); /* register character device /dev/mcelog */ misc_register(&mce_chrdev_device);