Path: utzoo!attcan!utgpu!watmath!watcgl!idallen
From: idallen@watcgl.waterloo.edu (Ian! D. Allen [CGL])
Newsgroups: comp.unix.wizards
Subject: Re: suspend question -- Berkeley kernels kill TSTP processes
Message-ID: <11512@watcgl.waterloo.edu>
Date: 18 Sep 89 05:13:26 GMT
References: <8397@boring.cwi.nl>
Reply-To: idallen@watcgl.waterloo.edu (Ian! D. Allen [CGL])
Organization: U. of Waterloo, Ontario
Lines: 24

Berkeley-derived unix kernels SIGKILL processes that receive SIGTSTP,
SIGTTOU, or SIGTTIN if they have no parent (parent pid == 1 [init]).  

Try this:

    % stty tostop
    % ( date & )
    % 

and you'll see no output from the date command.  Or, try:

    % ( sleep 999 & )
    % kill -TSTP <pidofsleep>
    % ps x

I quote the reason from sys/kern_sig.c:

			/*
			 * Don't clog system with children of init
			 * stopped from the keyboard.
			 */
-- 
-IAN! (Ian! D. Allen) idallen@watcgl.uwaterloo.ca idallen@watcgl.waterloo.edu
 129.97.128.64    Computer Graphics Lab/University of Waterloo/Ontario/Canada