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) 2017 by Delphix. All rights reserved.
  */
 
 /*
  *      Copyright (c) 1983,1984,1985,1986,1987,1988,1989  AT&T.

@@ -1392,11 +1393,11 @@
         struct nfs4_async_reqs *args;
         mntinfo4_t *mi = VFTOMI4(vfsp);
         clock_t time_left = 1;
         callb_cpr_t cprinfo;
         int i;
-        extern int nfs_async_timeout;
+        extern volatile int nfs_async_timeout;
         int async_types;
         kcondvar_t *async_work_cv;
 
         if (async_queue == NFS4_ASYNC_QUEUE) {
                 async_types = NFS4_ASYNC_TYPES;