update to reality from netbsd

1 files changed, 15 insertions, 46 deletions

diff --git a/lib/libc/sys/vfork.2 b/lib/libc/sys/vfork.2
index 55e184b2954..e363e74fc7e 100644
--- a/lib/libc/sys/vfork.2
+++ b/lib/libc/sys/vfork.2
@@ -1,4 +1,4 @@
-.\"	$NetBSD: vfork.2,v 1.6 1995/02/27 12:39:30 cgd Exp $
+.\"	$NetBSD: vfork.2,v 1.8 1997/07/10 07:54:13 mikel Exp $
 .\"
 .\" Copyright (c) 1980, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -33,66 +33,42 @@
 .\"
 .\"     @(#)vfork.2	8.1 (Berkeley) 6/4/93
 .\"
-.Dd June 4, 1993
+.Dd June 30, 1997
 .Dt VFORK 2
 .Os BSD 4
 .Sh NAME
 .Nm vfork
-.Nd spawn new process in a virtual memory efficient way
+.Nd spawn new process and block parent
 .Sh SYNOPSIS
 .Fd #include <unistd.h>
 .Ft pid_t
 .Fn vfork void
 .Sh DESCRIPTION
 .Fn Vfork
-can be used to create new processes without fully copying the address
+was originally used to create new processes without fully copying the address
 space of the old process, which is horrendously inefficient in a paged
-environment.  It is useful when the purpose of
+environment.  It was useful when the purpose of
 .Xr fork 2
 would have been to create a new system context for an
-.Xr execve 2 .
+.Xr execve .
+It is the case that 
+.Xr fork
+is now efficient, even in the above case, so that the need for
+.Fn vfork
+is diminished.
 .Fn Vfork
 differs from
-.Xr fork 2
-in that the child borrows the parent's memory and thread of
-control until a call to
+.Xr fork
+in that the parent is suspended until the child makes a call to
 .Xr execve 2
 or an exit (either by a call to
-.Xr exit 2
+.Xr _exit 2
 or abnormally.)
-The parent process is suspended while the child is using its resources.
 .Pp
 .Fn Vfork
 returns 0 in the child's context and (later) the pid of the child in
 the parent's context.
-.Pp
-.Fn Vfork
-can normally be used just like
-.Xr fork 2 .
-It does not work, however, to return while running in the childs context
-from the procedure that called
-.Fn vfork
-since the eventual return from
-.Fn vfork
-would then return to a no longer existent stack frame.
-Be careful, also, to call
-.Xr _exit 2
-rather than
-.Xr exit 3
-if you can't
-.Xr execve 2 ,
-since
-.Xr exit 3
-will flush and close standard I/O channels, and thereby mess up the
-parent processes standard I/O data structures.
-(Even with
-.Xr fork 2
-it is wrong to call
-.Xr exit 3
-since buffered data would then be flushed twice.)
 .Sh SEE ALSO
-.Xr _exit 2 ,
-.Xr exit 3 ,
 .Xr fork 2 ,
 .Xr execve 2 ,
 .Xr sigaction 2 ,
@@ -101,13 +77,6 @@ since buffered data would then be flushed twice.)
 Same as for
 .Xr fork 2 .
 .Sh BUGS
-This system call will be eliminated when proper system sharing
-mechanisms are implemented. 
-Users should not depend on the memory
-sharing semantics of
-.Xr vfork 2
-as it will, in that case, be made synonymous to
-.Xr fork 2 .
 .Pp
 To avoid a possible deadlock situation,
 processes that are children in the middle
@@ -127,4 +96,4 @@ and input attempts result in an end-of-file indication.
 The
 .Fn vfork
 function call appeared in
-.Bx 3.0 .
+.Bx 2.9 .