Path: utzoo!attcan!uunet!husc6!ogccse!blake!uw-beaver!cornell!rochester!rutgers!bellcore!texbell!bigtex!milano!cs.utexas.edu!sm.unisys.com!csun!polyslo!steve
From: steve@polyslo.CalPoly.EDU (Steve DeJarnett)
Newsgroups: news.sysadmin
Subject: Re: Outrageous amount of multiple forks
Message-ID: <5810@polyslo.CalPoly.EDU>
Date: 16 Nov 88 21:56:20 GMT
References: <22401@cornell.UUCP> <2210005@acf3.NYU.EDU> <382@ivucsb.UUCP>
Reply-To: steve@polyslo.CalPoly.EDU (Steve DeJarnett)
Organization: Lab Rat Rumpus Room -- Cal Poly SLO
Lines: 34

In article <382@ivucsb.UUCP> news@ivucsb.UUCP (Todd Day) writes:
>In article <2210005@acf3.NYU.EDU> rosenblg@acf3.NYU.EDU (Gary J. Rosenblum) writes:
>_On another note, today I found a student running this wonderful
>_little ditty, which he named oddly enough virus.c:
>_
>_main() { while (1) fork (); }
>_
>_and he effectively halted a small vax (11/750).
>
>Isn't there something to prevent this sort of system crashing?  It's
>all too easy...

	Well, we have this happen about one week out of every quarter.  The
faculty tell the students about fork() for some operating systems project or
for networking (or some such thing), but they fail to tell them how to use
fork properly (not that it's that difficult, but people manage to do what you
mentioned above all the time).  The only possible solutions we've found (short
of removing fork() from the libraries) is to limit CPU usage (you can do this
on BSD -- don't know about System V or other Unix variants).  The problem you
run into is people doing real work that need more CPU time than normal (maybe
only for one quarter).  Sure, you can change the allocation, but it's an
overhead that we (and many other places, I'm sure) don't want/need.  So, we
make broad, sweeping threats in the hopes of getting people to check their
code thoroughly before running it (but it does still happen).  You can either
put up with it (which is what we chose to do), or implement resource limits.

	Other than that, you're basically stuck.

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