From 1124bfbdf69015c9f00e587b056fa048e2df3199 Mon Sep 17 00:00:00 2001
From: Corey Minyard <cminyard@mvista.com>
Date: Mon, 11 Jul 2016 13:16:27 -0500
Subject: [PATCH 403/414] x86: Fix an RT MCE crash

On some x86 systems an MCE interrupt would come in before the kernel
was ready for it.  Looking at the latest RT code, it has similar
(but not quite the same) code, except it adds a bool that tells if
MCE handling is initialized.  That was required because they had
switched to use swork instead of a kernel thread.  Here, just
checking to see if the thread is NULL is good enough to see if
MCE handling is initialized.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 arch/x86/kernel/cpu/mcheck/mce.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 3a7ab0b08cdf..9901b77ed819 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1403,7 +1403,8 @@ static int mce_notify_work_init(void)
 
 static void mce_notify_work(void)
 {
-	wake_up_process(mce_notify_helper);
+	if (mce_notify_helper)
+		wake_up_process(mce_notify_helper);
 }
 #else
 static void mce_notify_work(void)
-- 
2.10.2

