From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on ip-172-31-74-118.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.5-pre1 Path: eternal-september.org!reader02.eternal-september.org!.POSTED!not-for-mail From: "J-P. Rosen" Newsgroups: comp.lang.ada Subject: Re: is there a version of unix written in Ada Date: Fri, 2 Oct 2020 09:42:02 +0200 Organization: Adalog Message-ID: References: <00cd3aaa-d518-43a2-b321-58d6fae70aebo@googlegroups.com> <57eb7a65-51ea-4624-b9dc-9c4dda0fee59n@googlegroups.com> <5f70fd3b$0$13541$426a74cc@news.free.fr> <87wo0d3iac.fsf@nightsong.com> <87sgb02l7b.fsf@nightsong.com> <875z7vyy1u.fsf@nightsong.com> <87wo0bkns3.fsf@nightsong.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Date: Fri, 2 Oct 2020 07:42:02 -0000 (UTC) Injection-Info: reader02.eternal-september.org; posting-host="b4fd8c57d77b003b02ecb9df47963ac0"; logging-data="12703"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18N8DZ6B/nDCmFLVNQTRtvc" User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 Cancel-Lock: sha1:9yavGYtAyRivE0J6DKDKO6wOX/I= In-Reply-To: Content-Language: fr Xref: reader02.eternal-september.org comp.lang.ada:60383 List-Id: Le 02/10/2020 à 08:56, Dmitry A. Kazakov a écrit : > On 02/10/2020 07:36, J-P. Rosen wrote: > >> To continue on Randy's response: mutual exclusion is not blocking. >> "Blocking" (as in "potentially blocking operation") means "being put on >> a queue", i.e. when the waiting time is potentially unbounded. > > It would be a poor definition, because deadlock in not bounded as well. > If jumping from one protected object to another is legal, we can > construct a deadlock out of mutual exclusion. But this would necessarily involve an "external call to the same protected object", which is defined as a potentially blocking operation. Note that AdaControl is quite powerful at detecting that situation (by following the call graph). > We also have a situation > when multiple tasks executing protected procedures are awaiting their > turn to enter a procedure of some object. They will continue (if not > deadlocked) in some order, which is obviously a queue. No, it can be implemented with a spin lock. It is bounded by the number of waiting tasks x service time. You don't have to wait for some unpredictable barrier. -- J-P. Rosen Adalog 2 rue du Docteur Lombard, 92441 Issy-les-Moulineaux CEDEX Tel: +33 1 45 29 21 52, Fax: +33 1 45 29 25 00 http://www.adalog.fr