[comp.unix.wizards] suspend question -- Berkeley kernels kill TSTP processes

D. Allen [CGL]) (09/18/89)

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

chris@mimsy.UUCP (Chris Torek) (09/18/89)

In article <11512@watcgl.waterloo.edu> idallen@watcgl.waterloo.edu
(Ian! D. Allen [CGL]) writes:
>Berkeley-derived unix kernels SIGKILL processes that receive SIGTSTP,
>SIGTTOU, or SIGTTIN if they have no parent (parent pid == 1 [init]).  

`Fixed in 4.4'

>    % stty tostop
>    % ( date & )
>    % 

[ucb2] stty tostop
[ucb3] (date &)
[ucb4] Mon Sep 18 06:00:20 PDT 1989
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris