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Subject[tip:x86/urgent] x86, MCE: Robustify mcheck_init_device
Commit-ID:  51cbe7e7c400def749950ab6b2c120624dbe21a7
Gitweb: http://git.kernel.org/tip/51cbe7e7c400def749950ab6b2c120624dbe21a7
Author: Borislav Petkov <bp@suse.de>
AuthorDate: Fri, 20 Jun 2014 23:16:45 +0200
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Mon, 21 Jul 2014 18:14:32 +0200

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 bb92f38..9a79c8d 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -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

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