5056 ZFS deadlock on db_mtx and dn_holds
Reviewed by: Will Andrews <willa@spectralogic.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

*** 19,28 ****
--- 19,29 ----
   * CDDL HEADER END
   */
  /*
   * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright (c) 2012 by Delphix. All rights reserved.
+  * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
   */
  
  #include <sys/dsl_dataset.h>
  #include <sys/dmu.h>
  #include <sys/refcount.h>
*** 117,126 ****
--- 118,129 ----
  dsl_deadlist_close(dsl_deadlist_t *dl)
  {
          void *cookie = NULL;
          dsl_deadlist_entry_t *dle;
  
+         dl->dl_os = NULL;
+ 
          if (dl->dl_oldfmt) {
                  dl->dl_oldfmt = B_FALSE;
                  bpobj_close(&dl->dl_bpobj);
                  return;
          }