re #13613 rb4516 Tunables needs volatile keyword

*** 18,27 ****
--- 18,28 ----
   *
   * CDDL HEADER END
   */
  /*
   * Copyright (c) 1990, 2010, Oracle and/or its affiliates. All rights reserved.
+  * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
   */
  
  #ifndef _SYS_MODCTL_H
  #define _SYS_MODCTL_H
  
*** 545,555 ****
   */
  extern kmutex_t mod_lock;
  
  extern char *systemfile;
  extern char **syscallnames;
! extern int moddebug;
  
  /*
   * this is the head of a doubly linked list.  Only the next and prev
   * pointers are used
   */
--- 546,556 ----
   */
  extern kmutex_t mod_lock;
  
  extern char *systemfile;
  extern char **syscallnames;
! extern volatile int moddebug;
  
  /*
   * this is the head of a doubly linked list.  Only the next and prev
   * pointers are used
   */