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" Newsgroups: comp.lang.ada Subject: Re: A question about task's select delay alternative Date: Mon, 23 Apr 2018 22:40:27 +0200 Organization: Aioe.org NNTP Server Message-ID: References: NNTP-Posting-Host: kQkuQcRDy1QFvWpyB1foYw.user.gioia.aioe.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@aioe.org User-Agent: Mozilla/5.0 (Windows NT 10.0; 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:51687 Date: 2018-04-23T22:40:27+02:00 List-Id: On 2018-04-23 19:32, NiGHTS wrote: > In a task with a select like this... > > task body X is > begin > loop > select > accept Y; > or > delay 10.0; > exit; > end select; > end loop; > end X; > > What does "delay" actually do to the CPU? In this case I am using the Adacore GNAT compiler for a PC. Is it a loop constantly evaluating elapsed time? Or is it some kind of timed interrupt? On most systems there is a way to do it in a non-busy manner. E.g. by waiting for a system waitable object with 10s timeout under Windows or doing same with a futex under Linux or by using pthreads API, whatever pleases the Ada RTS provider. When the entry is accepted/completed by the task scheduler, the object is signaled. Otherwise the timeout is expired and the thread is released with a different return code. In short, do not worry. -- Regards, Dmitry A. Kazakov http://www.dmitry-kazakov.de