From 64dd590ece7b4aaa41990dca511f91e50f22ba0d Mon Sep 17 00:00:00 2001
From: Andriy Gapon <avg@FreeBSD.org>
Date: Sat, 9 Oct 2010 08:07:49 +0000
Subject: [PATCH] panic_cpu variable should be volatile

This is to prevent caching of its value in a register when it is checked
and modified by multiple CPUs in parallel.
Also, move the variable  into the scope of the only function that uses it.

Reviewed by:	jhb
Hint from:	mdf
MFC after:	1 week
---
 sys/kern/kern_shutdown.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/sys/kern/kern_shutdown.c b/sys/kern/kern_shutdown.c
index 018bd8eecfd..0f1462380b5 100644
--- a/sys/kern/kern_shutdown.c
+++ b/sys/kern/kern_shutdown.c
@@ -513,10 +513,6 @@ shutdown_reset(void *junk, int howto)
 	/* NOTREACHED */ /* assuming reset worked */
 }
 
-#ifdef SMP
-static u_int panic_cpu = NOCPU;
-#endif
-
 /*
  * Panic is called on unresolvable fatal errors.  It prints "panic: mesg",
  * and then reboots.  If we are called twice, then we avoid trying to sync
@@ -525,6 +521,9 @@ static u_int panic_cpu = NOCPU;
 void
 panic(const char *fmt, ...)
 {
+#ifdef SMP
+	static volatile u_int panic_cpu = NOCPU;
+#endif
 	struct thread *td = curthread;
 	int bootopt, newpanic;
 	va_list ap;