Subject: kern/7499: Problem with serial terminals and persistent children processes
To: None <>
From: Brian Buhrow <>
List: netbsd-bugs
Date: 04/29/1999 14:21:34
>Number:         7499
>Category:       kern
>Synopsis:       Subshells of the window program do not receive SIGHUP when window exits.
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people (Kernel Bug People)
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Apr 29 14:20:00 1999
>Originator:     Brian Buhrow
	UC Santa Cruz
>Release:        NetBSD-current April 16, 1999
System: NetBSD 1.4_ALPHA NetBSD 1.4_ALPHA (GLORFINDEL) #2: Fri Apr 16 12:13:16 PDT 1999 i386

	<precise description of the problem (multiple lines)>
	If the window program, shipped with the distribution, is invoked from
a serial terminal session, i.e. through a hardware serial port, when the
window program exits, the shells it spawned in the various windows, along
with any processes they spawn, do not receive a SIGHUP signal.  They are
supposed to receive a SIGHUP signal when window exits, and this does work
when logging in through a telnet connection and a pseudo terminal.  As a
result, the user of the window program leaves a bunch of orfaned processes
on the system when he or she logs out unless he or she kills them manually
by sending a SIGHUP with the kill(1) program.
	This functionality worked in NetBSD 0.9, 1.0, 1.1 and 1.2, I haven't
been able to test 1.3, but my suspicion is that it works there as well.
I'm not sure where the problem is precisely, but I suspect that it is a
problem with the interaction of the com driver and the tty layer.  The i386
binary snapshot of March 15, 1999 shows the same behavior as the sources I
used April 16, 1999.  The versions of the com and kern_tty files are as
     $NetBSD: tty.c,v 1.112 1998/09/11 12:50:11 mycroft Exp $
     $NetBSD: com.c,v 1.159 1999/03/31 12:44:04 mrg Exp $

	Activate a getty process on a serial port.

	Use a terminal or terminal emulator to login through that serial port.
(I don't know if kermit through two separate serial ports on the same
computer would be a good test.)

	Once you have a shell, install the enclosed .windowrc file in your
home directory as  ~/.windowrc.

	Launch the window program.
%window -e^o

Determine the process id for one of the shells in one of the windows that
[1]%ps -uxw |grep 'p2
[1]%cd /var/tmp
[1]%ktrace -p [pid found above]
[1]%ls -l ktrace.out
-rw------ 1 [user] 50 Apr 28 15:50 ktrace.out
^oq [Really quit? [yn]: y]
%cd /var/tmp

%ls -l ktrace.out
-rw------ 1 [user] 50 Apr 28 15:50 ktrace.out

	If the size of the file is unchanged, then the shell is still running
and has not received its SIGHUP signal.  Otherwise, it will be about 495
bytes or so and will have exited.  The ^o syntax above indicates a command
to the window program itself and means issue a control-o.  The brackets
indicate which window you're working in.  The non-bracketed prompts
indicate you're working in the raw tty session.
	Here is the .windowrc file I use and have used since window ran on
Vaxen under 4.3BSD.  

nline 1000
select 1

	I don't know how to work around this problem at this time.