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From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: Need help with PowerPC/Ada and realtime tasking
Date: 1996/05/20
Message-ID: <EACHUS.96May20180337@spectre.mitre.org>#1/1
X-Deja-AN: 155816656
references: <d-struble.107.001A95C3@ti.com> <1026696wnr@diphi.demon.co.uk>
organization: The Mitre Corp., Bedford, MA.
newsgroups: comp.lang.ada
Date: 1996-05-20T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <1026696wnr@diphi.demon.co.uk> JP Thornley <jpt@diphi.demon.co.uk> writes:

  > My first response is that safety-critical software does not go well
  > with interrupts and the use of tasking.  The main requirement of 
  > safety-critical code is predictability, which is made impossible if
  > you are coping with unpredictable interrupts and with hard-to-analyse
  > tasking syncronisations.

  Your second sentence is correct, but the first doesn't follow...  If
you want to use tasking in a safety-critical system look at the work
on hard deadline scheduling by Liu and Goodenough at the SEI.  It
works, it can be a pain to work through unless you have good tools,
but it works reliably.

   If there are only a few tasks, and the timing is not too tight,  a
cyclic executive is a reasonable alternative.


--

					Robert I. Eachus

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