Path: utzoo!censor!geac!torsqnt!jarvis.csri.toronto.edu!dgp.toronto.edu!lansd
From: lansd@dgp.toronto.edu (Robert Lansdale)
Newsgroups: comp.sys.sgi
Subject: How to kill tasks after a user abort?
Message-ID: <1990Mar4.121456.14599@jarvis.csri.toronto.edu>
Date: 4 Mar 90 17:14:56 GMT
Distribution: na
Lines: 31


	I have been running my 3d renderer successfully in parallel
on our 4D/140 for several months now, but I have yet to get the ^C
signal handling (SIGINT) to terminate the tasks gracefully. 

	My renderer is set up so the user may abort the display process
(which runs in parallel using tasks distributed with taskcreate()) by
typing ^C, at which point the signal handler shuts the display code down
and kills any stray tasks (I've noticed that random tasks get killed when
SIGINT is seen - is this documented anywhere??). The signal handler then
does a long jump back to the command line parser. The parent process is
usually asleep while the tasks are running (it distributes work to the
tasks and goes to sleep in a uspsema() statement).

	So how do I assure that the parent process gets woken and becomes
the first process to enter the signal handler? I've (carefully) read through
the signal man page several times and tried a number of variations of the 
SIGCLD signal catcher, but I still find that the parent process is getting
stuck occansionally in the printf() routine when it is about to print that 
the display code is shutdown (printf() -> Psema() -> blockproc() ...). This
printf() is part of the signal handling code.

	Any pointers would be most appreciated. Thanks.

--> Rob Lansdale

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Robert Lansdale - (416) 978-6619       Dynamic Graphics Project	
Internet: lansd@dgp.toronto.edu        Computer Systems Research Institute
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Bitnet:	  lansd@dgp.utoronto           Toronto, Ontario M5S 1A4, CANADA