Index: kern_fork.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_fork.c,v
retrieving revision 1.257
diff -u -r1.257 kern_fork.c
--- kern_fork.c	8 Feb 2006 08:09:16 -0000	1.257
+++ kern_fork.c	15 Mar 2006 07:19:27 -0000
@@ -220,6 +220,16 @@
 	 * certain parts of a process from itself.
 	 */
 	if ((flags & RFPROC) == 0) {
+		if ((p1->p_flag & P_HADTHREADS) &&
+		    (flags & (RFCFDG | RFFDG))) {
+			PROC_LOCK(p1);
+			if (thread_single(SINGLE_BOUNDARY)) {
+				PROC_UNLOCK(p1);
+				return (ERESTART);
+			}
+			PROC_UNLOCK(p1);
+		}
+
 		vm_forkproc(td, NULL, NULL, flags);
 
 		/*
@@ -237,6 +247,13 @@
 		 */
 		if (flags & RFFDG) 
 			fdunshare(p1, td);
+
+		if ((p1->p_flag & P_HADTHREADS) &&
+		    (flags & (RFCFDG | RFFDG))) {
+			PROC_LOCK(p1);
+			thread_single_end();
+			PROC_UNLOCK(p1);
+		}
 		*procp = NULL;
 		return (0);
 	}