From 27c934158c5be0bebfb2970da521b9d9efc0058b Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@suse.de>
Date: Fri, 20 Jun 2014 23:16:45 +0200
Subject: [PATCH] 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>
---
arch/x86/kernel/cpu/mcheck/mce.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 8fecdd34f2d2d..4fc57975acc1c 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -2450,6 +2450,12 @@ 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;
}
@@ -2470,10 +2476,6 @@ 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
--
2.30.2