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From: eachus@mitre-bedford.ARPA (Robert Eachus)
Newsgroups: comp.sys.amiga.tech
Subject: Negative Open Counts (was Re: IEEE libraries)
Summary: A compatible fix.
Keywords: open counts
Message-ID: <39822@linus.UUCP>
Date: 12 Sep 88 19:02:13 GMT
References: <1356@percival.UUCP> <b03Kac9bnd10108qAIk@amdahl.uts.amdahl.com> <358@boing.UUCP> <1570@sbcs.sunysb.edu> <362@boing.UUCP>
Sender: news@linus.UUCP
Reply-To: eachus@mitre-bedford.ARPA (Robert I. Eachus)
Distribution: na
Organization: The MITRE Corporation, Bedford, Mass.
Lines: 35


     What we need is an upwardly compatible solution which does not
cause existing correct programs to Guru if some other task fouls
things up.  The following suggestion points the way:

>In article <1570@sbcs.sunysb.edu> root@sbcs.sunysb.edu (root) writes:
>>
>>	No, please no more GURU conditions.  It seems to be that a reasonable
>>	thing to do is when the count would go negative just mark the
>>	library as permanently open and ignore any further closes.

     If setting the open  count  negative makes a library  permanently
resident (at least  till the  next warm boot, or someone intentionally
diddles the bits) we get the following rule:

     When a  library is opened  by a task, if the (open) count is
     non-negative, increment it by one.  When a library is closed
     decrement  the count by one.  Libraries may only be unloaded
     when the count is zero.

     Simple and sweet.  I like the idea  of ratcheting the count down,
but  setting all negative  counts to minus  one or some other value is
equally acceptable.    In   any case, other  than  to  very  simple OS
changes,  no   fuss, no  bother.   It might  be nice   to  add a  make
permanently resident call, and  a  force unload utility, but these are
frills.  And it is all  very  useful. A library  could force itself to
stay resident  if it opened a  resouce behind the users  back  when it
needed to maintain state.  (Such a library would have to track itself,
but this shouldn't be hard if it is needed.)


					Robert I. Eachus

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