re #13613 rb4516 Tunables needs volatile keyword

@@ -18,10 +18,11 @@
  *
  * CDDL HEADER END
  */
 /*
  * Copyright (c) 1986, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
  */
 
 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
 /*        All Rights Reserved   */
 

@@ -672,11 +673,11 @@
 extern  pgcnt_t total_pages;            /* total pages in the system */
 
 /*
  * Variables controlling locking of physical memory.
  */
-extern  pgcnt_t pages_pp_maximum;       /* tuning: lock + claim <= max */
+extern  volatile pgcnt_t pages_pp_maximum; /* tuning: lock + claim <= max */
 extern  void init_pages_pp_maximum(void);
 
 struct lgrp;
 
 /* page_list_{add,sub} flags */