re #13613 rb4516 Tunables needs volatile keyword

@@ -20,10 +20,13 @@
  */
 /*
  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
+/*
+ * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
+ */
 
 /*
  * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 

@@ -198,11 +201,11 @@
 /* lwp states */
 #define LWP_USER        0x01            /* Running in user mode */
 #define LWP_SYS         0x02            /* Running in kernel mode */
 
 #if     defined(_KERNEL)
-extern  int     lwp_default_stksize;
+extern  volatile int    lwp_default_stksize;
 extern  int     lwp_reapcnt;
 
 extern  struct _kthread *lwp_deathrow;
 extern  kmutex_t        reaplock;
 extern  struct kmem_cache *lwp_cache;