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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Finalization of library level tasks
Date: Tue, 17 Apr 2018 16:47:10 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:51557
Date: 2018-04-17T16:47:10+02:00
List-Id: <comp.lang.ada>

On 17/04/2018 16:08, J-P. Rosen wrote:
> Le 17/04/2018 à 14:47, Dmitry A. Kazakov a écrit :
>> I don't understand the meaning of "revive". The meaning of
>>
>>     select
>>        terminate;
>>     else
>>        null;
>>     end select;
>>
>> is crystal clear: continue if no master did request termination else
>> continue. Again, I thought that T'Callable were there to determine if a
>> master wants the task to terminate.
> It's just that your mental model of 'Callable and Terminate is not the
> one of Ada. A master does not require termination from its dependent
> tasks: it checks (recursively) if all the dependent tasks are either
> already terminated or similarly waiting on a select-with-terminate. If
> yes, the whole family terminates simultaneously.

That simply cannot work. The task (or task manager) must know if the 
terminate alternative can be selected. That depends on the master's 
state. Master or something on its behalf must tell the task that it must 
start selecting terminate alternatives.

> When a master is waiting for dependent tasks to terminate (at its end,
> NOT if on a select-with-terminate), it is not yet Terminated, but it is
> no more Callable.

In that case

    task body T is
    begin
       while T'Callable loop
          ...
       end loop;
    end T;

must work, GNAT is correct, I am happy.

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