re #13613 rb4516 Tunables needs volatile keyword

@@ -19,10 +19,11 @@
  * CDDL HEADER END
  */
 
 /*
  * Copyright (c) 1991, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
  * Copyright (c) 2013, Joyent, Inc.  All rights reserved.
  */
 
 #include <sys/types.h>
 #include <sys/param.h>

@@ -118,12 +119,12 @@
 #define MIN_STKSIZE     DEFAULTSTKSZ
 
 /*
  * default_stksize overrides lwp_default_stksize if it is set.
  */
-int     default_stksize;
-int     lwp_default_stksize;
+volatile int    default_stksize;
+volatile int    lwp_default_stksize;
 
 static zone_key_t zone_thread_key;
 
 unsigned int kmem_stackinfo;            /* stackinfo feature on-off */
 kmem_stkinfo_t *kmem_stkinfo_log;       /* stackinfo circular log */