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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Problem with task component
Date: Tue, 25 Sep 2012 09:35:13 +0200
Organization: cbb software GmbH
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Date: 2012-09-25T09:35:13+02:00
List-Id: <comp.lang.ada>

On Mon, 24 Sep 2012 22:49:07 +0200, J-P. Rosen wrote:

> Le 24/09/2012 18:29, Dmitry A. Kazakov a �crit :
>> Else-alternative is no less important than delay. We need something like
>> 
>>    select
>>       terminate; -- Terminate if requested otherwise continue
>>    else
>>       null;
>>    end select;
> Which is of course undecidable.

Tasks behavior is undecidable most of the time. I dare to say that tasks
were useless when behaved in a decidable manner.

It does not make sense to require something from specifically task
termination, when the rest is not constrained. And it does not work,
anyway, because it is in no way to prevent deadlocking upon task
finalization. Happens all the time in Ada.

> If the master is on a select-or-terminate, what should the task do?

I propose a competing rule:

   Selection of the terminate alternative by the master shall not depend on
the states of the client tasks.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de