Commit 51cbe7e7 authored Jun 20, 2014 by Borislav Petkov

x86, MCE: Robustify mcheck_init_device

BorisO reports that misc_register() fails often on xen. The current code
unregisters the CPU hotplug notifier in that case. If then a CPU is
offlined and onlined back again, we end up with a second timer running
on that CPU, leading to soft lockups and system hangs.

So let's leave the hotcpu notifier always registered - even if
mce_device_create failed for some cores and never unreg it so that we
can deal with the timer handling accordingly.

Reported-and-Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: http://lkml.kernel.org/r/1403274493-1371-1-git-send-email-boris.ostrovsky@oracle.com

Signed-off-by: Borislav Petkov <bp@suse.de>

parent 9a3c4145

arch/x86/kernel/cpu/mcheck/mce.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -2451,6 +2451,12 @@ static __init int mcheck_init_device(void)
		for_each_online_cpu(i) {
		err = mce_device_create(i);
		if (err) {
		/*
		* Register notifier anyway (and do not unreg it) so
		* that we don't leave undeleted timers, see notifier
		* callback above.
		*/
		__register_hotcpu_notifier(&mce_cpu_notifier);
		cpu_notifier_register_done();
		goto err_device_create;
		}
		@@ -2471,10 +2477,6 @@ static __init int mcheck_init_device(void)
		err_register:
		unregister_syscore_ops(&mce_syscore_ops);

		cpu_notifier_register_begin();
		__unregister_hotcpu_notifier(&mce_cpu_notifier);
		cpu_notifier_register_done();

		err_device_create:
		/*
		* We didn't keep track of which devices were created above, but