From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,97ae587931c0f702
X-Google-Attributes: gid103376,public
From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: Ada Task priorities
Date: 1997/01/28
Message-ID: <EACHUS.97Jan27210405@spectre.mitre.org>#1/1
X-Deja-AN: 212638199
references: <kmradke-2601971335300001@dip7.inav.net> <dewar.854313404@merv>
organization: The Mitre Corp., Bedford, MA.
newsgroups: comp.lang.ada
Date: 1997-01-28T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <dewar.854313404@merv> dewar@merv.cs.nyu.edu (Robert Dewar) writes:

  >> Can one guarantee that if all 3 tasks are eligible for execution
  >> at the same time, that task a will finish it's work before
  >> task b begins to run, and task c will only run after both
  >> tasks a and b finish? (Assuming no tasks rendezvous with
  >> other tasks during this time?)
  >> I suppose even OS calls would make this highly platform dependent.

  >   Of course not, think multiprocessors for a moment!

  Quite correct. There is another case to keep in mind.  If task a and
b read from disk, it is perfectly legitimate (in Ada 83 or 95) for c
to run while waiting for the I/O to complete.  This is usually a
special case of multiprocessing, but one most people overlook in
desktop systems.  (In embedded systems, I/O latencies are carefully
calculated and there is unlikely to be any disk I/O of any kind. ;-)

  In Ada it is possible to cover all the bases and get predicable
tasking behavior, but in modern systems you really have to understand
the underlying hardware design.

--

					Robert I. Eachus

with Standard_Disclaimer;
use  Standard_Disclaimer;
function Message (Text: in Clever_Ideas) return Better_Ideas is...