[src/netbsd-9]: src/bin/sh Pull up following revision(s) (requested by kre in...

[martin <martin%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/5d04869bcad0
branches:  netbsd-9
changeset: 843714:5d04869bcad0
user:      martin <martin%NetBSD.org@localhost>
date:      Thu Dec 26 20:16:47 2019 +0000

description:
Pull up following revision(s) (requested by kre in ticket #582):

        bin/sh/eval.c: revision 1.177

Use fork() rather than vfork() when forking to run a background
process with redirects.   If we use vfork() and a redirect hangs
(eg: opening a fifo) which the parent was intended to unhang,
then the parent never gets to continue to unhang the child.
eg:  mkfifo f; cat <f &; echo foo>f

The parent should not be waiting for a background process, even
just for its exec() to complete.   if there are no redirects there
is (should be) nothing left that might be done that will cause any
noticeable delay, so vfork() should be safe in all other cases.

diffstat:

 bin/sh/eval.c |  9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diffs (38 lines):

diff -r 71d37e57a4e6 -r 5d04869bcad0 bin/sh/eval.c
--- a/bin/sh/eval.c     Tue Dec 24 17:47:14 2019 +0000
+++ b/bin/sh/eval.c     Thu Dec 26 20:16:47 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: eval.c,v 1.175.2.1 2019/12/11 14:52:50 martin Exp $    */
+/*     $NetBSD: eval.c,v 1.175.2.2 2019/12/26 20:16:47 martin Exp $    */
 
 /*-
  * Copyright (c) 1993
@@ -37,7 +37,7 @@
 #if 0
 static char sccsid[] = "@(#)eval.c     8.9 (Berkeley) 6/8/95";
 #else
-__RCSID("$NetBSD: eval.c,v 1.175.2.1 2019/12/11 14:52:50 martin Exp $");
+__RCSID("$NetBSD: eval.c,v 1.175.2.2 2019/12/26 20:16:47 martin Exp $");
 #endif
 #endif /* not lint */
 
@@ -552,8 +552,8 @@
            forkshell(jp = makejob(n, 1), n, backgnd?FORK_BG:FORK_FG) == 0) {
                if (backgnd)
                        flags &=~ EV_TESTED;
+               INTON;
                redirect(n->nredir.redirect, REDIR_KEEP);
-               INTON;
                evaltree(n->nredir.n, flags | EV_EXIT);   /* never returns */
        } else if (backgnd)
                exitstatus = 0;
@@ -1086,7 +1086,8 @@
                 * child's address space is actually shared with the parent as
                 * we rely on this.
                 */
-               if (usefork == 0 && cmdentry.cmdtype == CMDNORMAL) {
+               if (usefork == 0 && cmdentry.cmdtype == CMDNORMAL &&
+                   (!cmd->ncmd.backgnd || cmd->ncmd.redirect == NULL)) {
                        pid_t   pid;
                        int serrno;