From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!aioe.org!.POSTED!not-for-mail
From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Finalization of library level tasks
Date: Wed, 18 Apr 2018 13:58:00 +0200
Organization: Aioe.org NNTP Server
Message-ID: <pb7bs8$1olg$1@gioia.aioe.org>
References: <pavkou$1go7$1@gioia.aioe.org> <pavm21$ko5$1@dont-email.me>
 <pavmla$1k1o$1@gioia.aioe.org> <pavp2a$81n$1@dont-email.me>
 <pavqa6$1qdj$1@gioia.aioe.org>
 <702e2422-a93f-4200-9749-5122c3d0f899@googlegroups.com>
 <e55e3c35-5f4d-4a6c-a053-b76cf91268d5@googlegroups.com>
 <pb02qj$a5t$1@gioia.aioe.org> <pb1bpo$48m$1@gioia.aioe.org>
 <pb1jec$gnl$1@gioia.aioe.org> <pb1kta$ja4$1@gioia.aioe.org>
 <pb1lum$loe$1@gioia.aioe.org> <pb1n3o$nt9$1@gioia.aioe.org>
 <pb2fbf$516$1@gioia.aioe.org>
 <04f19a56-7fab-416e-8ec0-b9a73e239e90@googlegroups.com>
 <pb4pep$1nov$1@gioia.aioe.org>
 <da57e8f5-8fa3-4144-9c82-5ca1fa623886@googlegroups.com>
 <pb6veb$139g$1@gioia.aioe.org>
 <f6f94430-17eb-4d9d-8713-145ade3eb8b3@googlegroups.com>
 <pb74sr$1cmf$1@gioia.aioe.org> <pb7aeq$1m8j$1@gioia.aioe.org>
NNTP-Posting-Host: MyFhHs417jM9AgzRpXn7yg.user.gioia.aioe.org
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
X-Complaints-To: abuse@aioe.org
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.7.0
X-Notice: Filtered by postfilter v. 0.8.3
Content-Language: en-US
Xref: reader02.eternal-september.org comp.lang.ada:51582
Date: 2018-04-18T13:58:00+02:00
List-Id: <comp.lang.ada>

On 18/04/2018 13:33, J-P. Rosen wrote:
> Le 18/04/2018 à 11:58, Dmitry A. Kazakov a écrit :
>> can be emulated using Callable on the helper task:
>>
>>     task Helper is
>>        entry Never;
>>     end Helper;
>>
>>     task body Helper is
>>     begin
>>        select
>>           accept Never;
>>        or terminate;
>>        end select;
>>     end Helper;
>>
>>     task body Worker_Task is
>>     begin
>>        while Helper'Callable loop
>>           ... -- Do something
>>        end loop;
>>     end Worker_Task;
>>
>> When Helper and Worker_Task have same master then Worker_Task can break
>> finalization deadlock by looking at the Helper.
> Won't work. Please read 9.3(6/1):
>   the open terminate_alternative is selected if and only if the following
> conditions are satisfied:
> - The task depends on some completed master; and
> - Each task that depends on the master considered is either already
> terminated or similarly blocked at a select_statement with an open
> terminate_alternative.

(plus a race condition in tow. One could construct a case when a couple 
of tasks will never terminate calling each other to ensure that at a 
time at least two of them do not offer terminate alternative. How nice)

> Since Worker_Task and Helper depend on the same master, and Worker_Task
> is still busy, Helper won't select the terminate alternative, and will
> be still Callable.

Well, it seems broken beyond repair then. Let me guess, there going to 
be no change to fix the mess. Right?

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