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!news.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail From: Simon Wright Newsgroups: comp.lang.ada Subject: Re: Two-stage suspend operations Date: Tue, 10 May 2016 06:46:05 +0100 Organization: A noiseless patient Spider Message-ID: References: <9e93195a-eba0-4793-a64c-a24613090b3c@googlegroups.com> <95d6e489-463b-484b-b67e-8d37812f6b11@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: mx02.eternal-september.org; posting-host="078609b24ac737343a0c37340c7a7a6a"; logging-data="20622"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19QjelZaJEBE5QLKC5RTFLRIDz1iy5xXKc=" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (darwin) Cancel-Lock: sha1:2Kbvx2M1MClQhVvi42c8mxvAlEo= sha1:BKihDUPT41Mg2PaVevG9RQCG+Cg= Xref: news.eternal-september.org comp.lang.ada:30369 Date: 2016-05-10T06:46:05+01:00 List-Id: rieachus@comcast.net writes: > On Monday, May 9, 2016 at 4:56:15 AM UTC-4, Simon Wright wrote: >> I see what you mean. It's just that the wording in the ARM made it sound >> as though "two-stage suspend operations" was a phrase widely known in >> the community, which clearly isn't the case. > > If you look at this article from Wikipedia: > https://en.wikipedia.org/wiki/Two-phase_locking and go down to "strong > strict two-phase locking" you will see that it is not you, me or the > Ada Rationale. There are a lot of inconsistent names floating around > in this area, and the Rationale apparently chose one that lost > out. (Strong strict two-phase locking may not interest you, I just > picked the article as one showing considerable name confusion in > 2011.) Yes. I think part of my confusion is that the example in the Rationale doesn't actually involve locking at all. > I'm curious as to why you are interested in this area. Ada is a great > language for implementing in memory databases. At MITRE I worked on > both ground based and in-flight radar systems. The emphasis was on > consistency and non-blocking. I'm looking at a system[1] where I'm assured that we need to run a drone's motor controller at 20 kHz, and SOs seemed a possibility. Of course, if you need to avoid concurrency problems between a timer-driven ISR and tasking code, using SOs isn't going to work! so we are looking at swing-buffering or possibly GNAT's Lock_Free pragma/aspect[2]. [1] http://adapilot.likeabird.eu/index.html [2] https://gcc.gnu.org/onlinedocs/gnat_rm/Pragma-Lock_005fFree.html