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From: agnew@trwrc.UUCP (R.A. Agnew)
Newsgroups: comp.lang.ada
Subject: Re: Answer to 'a question'
Message-ID: <219@trwrc.UUCP>
Date: Fri, 4-Sep-87 12:58:38 EDT
Article-I.D.: trwrc.219
Posted: Fri Sep  4 12:58:38 1987
Date-Received: Sat, 5-Sep-87 23:07:27 EDT
References: <1987.8.27.15.36.30.Alfred.Peterson@sei.cmu.edu> <2181@cxsea.UUCP>
Reply-To: agnew@trwrc.UUCP (R.A. Agnew)
Organization: TRW/MEAD San Diego, Ca.
List-Id: <comp.lang.ada>

In article <2181@cxsea.UUCP> young@cxsea.UUCP (Gary Young) writes:
>|>My question is: Are those entry calls queued in the order of calls?
>|>YES. ... The key is that the execution of the
>
>Unfortunately, you are assuming a single processor system.  In any distributed
>or multiprocessor system, where calls are implemented via message exchange,

Wrong! Not in any OS. In a properly designed real-time, multiprocessor,
Ada OS, where tasking across machine boundaries is implemented via messages,
the design of the bus insures that the messages are received in the order
that they are sent out. A common solution is a ring bus such as the SAE-9B
token-passing ring. Why would the communication of a rendezvous over a
interprocessor bus between run-time systems in different kernals be any
different than passing a message from a task to a run-time kernal
in the same processor via system services? There are many synchronization
problems to be reconed with in these implementations and that is why it has
taken Ada contractors over five years to get even close to a solution.
As an example all processors are synchronized within nanoseconds by a
"heartbeat" signal and messages are time-tagged to resolve ambiguities between
real-time events.

	********** These opinions are solely my own **************