Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/3/83; site utcsrgv.UUCP
Path: utzoo!utcsrgv!dave
From: dave@utcsrgv.UUCP (Dave Sherman)
Newsgroups: net.bugs.uucp
Subject: Re: LCK. files and cu (low flame)
Message-ID: <2227@utcsrgv.UUCP>
Date: Mon, 12-Sep-83 15:38:19 EDT
Article-I.D.: utcsrgv.2227
Posted: Mon Sep 12 15:38:19 1983
Date-Received: Mon, 12-Sep-83 16:02:20 EDT
References: <1003@ittvax.UUCP>
Organization: The Law Society of Upper Canada, Toronto
Lines: 21

Alan Watt has a point about exclusive use having to be set after the
file is open, causing a race condition.

Maybe this is time to consider adding options to open() which can
be OR'ed into the higher bits of the second argument. Exclusive-use
is an obvious candidate. Presumably, it wouldn't be hard to change
stdio to add some letter (say, 'e') to the fopen call (e.g.,
fopen(iop, "we")), if necessary. Then again, I can see this leading
to a horribly complex system, with a lot of overlap between open
and ioctl, once it extends beyond exclusive-use.

Incidentally, not all drivers implement TIOCEXCL. (Yes, Virginia,
exclusive-use is implemented in the *driver*.) I have had to add
a check for ISOPEN&XCLUDE to both the kl.c (DLV-11J) and dz.c (DZV-11)
drivers on the lsuc 11/23 running v7.

Dave Sherman
The Law Society of Upper Canada
Toronto
-- 
 {cornell,decvax,floyd,ihnp4,linus,utzoo,uw-beaver,watmath}!utcsrgv!lsuc!dave