2916 DTrace in a zone should be able to access fds[]

@@ -19,10 +19,11 @@
  * CDDL HEADER END
  */
 
 /*
  * Copyright (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012, Joyent Inc. All rights reserved.
  */
 
 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
 /*      All Rights Reserved */
 

@@ -52,10 +53,11 @@
 #include <sys/atomic.h>
 #include <sys/fcntl.h>
 #include <sys/poll.h>
 #include <sys/rctl.h>
 #include <sys/port_impl.h>
+#include <sys/dtrace.h>
 
 #include <c2/audit.h>
 #include <sys/nbmlock.h>
 
 #ifdef DEBUG

@@ -950,10 +952,22 @@
                 return (error);
         }
         ASSERT(fp->f_count == 0);
         mutex_exit(&fp->f_tlock);
 
+        /*
+         * If DTrace has getf() subroutines active, it will set dtrace_closef
+         * to point to code that implements a barrier with respect to probe
+         * context.  This must be called before the file_t is freed (and the
+         * vnode that it refers to is released) -- but it must be after the
+         * file_t has been removed from the uf_entry_t.  That is, there must
+         * be no way for a racing getf() in probe context to yield the fp that
+         * we're operating upon.
+         */
+        if (dtrace_closef != NULL)
+                (*dtrace_closef)();
+
         VN_RELE(vp);
         /*
          * deallocate resources to audit_data
          */
         if (audit_active)