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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Finalization of library level tasks
Date: Wed, 18 Apr 2018 23:00:53 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:51620
Date: 2018-04-18T23:00:53+02:00
List-Id: <comp.lang.ada>

On 2018-04-18 22:26, AdaMagica wrote:
> Am Mittwoch, 18. April 2018 17:04:58 UTC+2 schrieb Dmitry A. Kazakov:
>> On 18/04/2018 16:52, J-P. Rosen wrote:
>>> Le 18/04/2018 à 16:12, Dmitry A. Kazakov a écrit :
>>>> In pseudo-code:
>>>>
>>>>      task body Worker is
>>>>      begin
>>>>         while the object lives loop
>>>>            do some chunk of work
>>>>         end loop;
>>>>      end Worker;
>>>>
>>>> P.S. I posted an example in a separate thread. The posted solution
>>>> should work except the cases when the access type is at the same level
>>>> as the object and both are below the library level.
>>>>
>>> OK. You were actually quite close... Use a killer task (with the same
>>> master as your worker) like this:
>>>
>>> task Killer is
>>>      entry Never_Called;
>>> end Killer;
>>>
>>> task body Killer is
>>> begin
>>>      accept Never_Called;
>>> exception
>>>      when Tasking_Error =>
>>>        -- Kill the other task
>>> end Killer;
>>>
>>> Hint: when the master completes, Tasking_Error is raised in all tasks
>>> waiting on entries that depend on that master.
>>
>> Does it raise for all entries? If it does no killer task is needed:
>>
>>      task body Worker is
>>      begin
>>         loop
>>            begin
>>               select
>>                  accept Never;
>>               else
>>                  null;
>>               end select;
>>            exception
>>               when Tasking_Eror =>
>>                  exit;
>>            end;
>>            do some chunk of work
>>         end loop;
>>      end Worker;
>>
>> Should this work?
> 
> No, because it's not waiting at the rendezvous.

Strange semantics, at least. How about this:

    task body Worker is
    begin
       loop
          begin
             select
                accept Never;
             or delay 0.000_001;
             end select;
          exception
             when Tasking_Eror =>
                exit;
          end;
          do some chunk of work
       end loop;
    end Worker;

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