Re: Tasking and delays, again

[wes@wsccs.UUCP (Barnacle Wes)]

In article <8802160441.AA16876@ajpo.sei.cmu.edu>, MFELDMAN@GWUVM.BITNET (Mike Feldman) writes:
> 1. A and B have the same priority
> 
> 2. A has higher priority than B
> 
> 3. B has higher priority than A
> 
> If I read the recent discussion of AI-something correctly, a legal
> system in which 2 or 3 is even possible must, somehow, interrupt. Am
> I correct in this reading? Does it make any difference if case 1
> obtains?
> 

I can't answer your questions, unfortunately, but I do know of some code for
an Air Force command and control system that would break (horribly) if the
Ada compiler did not support pre-emption.  By pre-emption I mean:

	process A has a higher priority than process B
	process B is currently running
	process A becomes ready to run due to some event

most of the executives I have worked on in command and control systems need
to be guaranteed that A will run within a specified amount of time, or they
would not work at all.  C2 messages would be scrambled or lost.  Does the
Ada language allow tasking systems that do not support time-slicing of some
sort on single-processor systems?
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