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From: Andriy Gapon <avg@FreeBSD.org>
Date: Sat, 9 Oct 2010 08:07:49 +0000 (UTC)
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Subject: svn commit: r213648 - head/sys/kern
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Author: avg
Date: Sat Oct  9 08:07:49 2010
New Revision: 213648
URL: http://svn.freebsd.org/changeset/base/213648

Log:
  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

Modified:
  head/sys/kern/kern_shutdown.c

Modified: head/sys/kern/kern_shutdown.c
==============================================================================
--- head/sys/kern/kern_shutdown.c	Sat Oct  9 07:45:24 2010	(r213647)
+++ head/sys/kern/kern_shutdown.c	Sat Oct  9 08:07:49 2010	(r213648)
@@ -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;