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From: md@sco.COM (Michael Davidson)
Newsgroups: comp.unix.programmer
Subject: Re: possible race condition?
Message-ID: <12141@scolex.sco.COM>
Date: 20 May 91 17:09:56 GMT
Article-I.D.: scolex.12141
References: <1991May9.144935.20078@ge-dab.GE.COM> <1991May9.182241.17090@robobar.co.uk> <1991May11.073648.1970@am.sublink.org>
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alex@am.sublink.org (Alex Martelli) writes:

>ronald@robobar.co.uk (Ronald S H Khoo) writes:
>	...
>:Part of the System V interface definition apparently guarantees the
>:child to execute before the parent, I hear -- I'd like chapter and
>:verse from someone who has a copy, if that's not too much trouble.
>Does not look that way to me - SVID 2, p.86, under fork(ba_os), says
>"both processes will run as system resources become available".

>:So, in principle, yes, you're right, but the code works correctly
>:on "real" System V.
>It's possibly that way depending on how it is *implemented*, but it
>does not seem to me that you get any guarantee from the interface
>*specification*.

The SVID does *not* specify whether the child process or the
parent process must execute first. Unfortunately many of the
SVVS tests are rather badly written and have unpleasant timing
windows in them - something you find out as soon as you try to
run SVVS on a multiprocessor system where it is quite possible
that the parent and child will run simultaneously on different
processors.