Path: utzoo!attcan!uunet!husc6!uwvax!oddjob!gargoyle!att!ihnp4!poseidon!ech
From: ech@poseidon.UUCP (Edward C Horvath)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Re: what the heck is "reentrant"?
Message-ID: <465@poseidon.UUCP>
Date: 8 Aug 88 19:01:14 GMT
References: <104700046@p.cs.uiuc.edu>
Organization: AT&T Information Systems, Lincroft, NJ
Lines: 17

> Nf-ID: #R:hpcilzb.HP.COM:730049:p.cs.uiuc.edu:104700046:000:808
> Nf-From: p.cs.uiuc.edu!gillies    Aug  3 18:44:00 1988


> Here are a few common ways to make something NON-reentrant:
...

It's actually pretty easy: anything which modifies a statically-allocated
variable potentially loses reentrancy.  Consider
	i := i + 1;
If one copy of the program loads i, then another copy runs through the
whole statement, then the first copy completes, i winds up incremented
only once.  This kind of thing is particularly nasty, couse you only get
interrupts in that 10-microsecond "window of vulnerability" when the
system is already deployed in the field :-)

=Ned Horvath=