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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,a3ca574fc2007430 X-Google-Attributes: gid103376,public X-Google-Thread: 115aec,f41f1f25333fa601 X-Google-Attributes: gid115aec,public From: Ken Garlington Subject: Re: Ada and Automotive Industry Date: 1996/11/08 Message-ID: <3283260C.7F5B@lmtas.lmco.com>#1/1 X-Deja-AN: 195316800 references: <55ea3g$m1j@newsbf02.news.aol.com> <3280DA96.15FB@hso.link.com> content-type: text/plain; charset=us-ascii organization: Lockheed Martin Tactical Aircraft Systems mime-version: 1.0 newsgroups: comp.lang.ada,comp.realtime x-mailer: Mozilla 2.02 (Macintosh; I; 68K) Date: 1996-11-08T00:00:00+00:00 List-Id: Robert I. Eachus wrote: > > > In Ada 83 you can't schedule a periodic event reliably -- no Ada > > task was guaranteed to run at the time requested. Everyone I knew > > who used Ada for avionics in the 80s wrote their own scheduler. > > A HUGE amount of wasted effort because people couldn't be bothered > to read the reference manual. What the Ada 83 RM said, and pretty > plainly at that, was that a critical task would run exactly (within > the limits of accuracy of the physical clock, etc.) when scheduled, > unless there was an equal or higher priority task using every > available processor. There was even an AI, published as a > ramification, titled "Preemptive scheduling is required" (AI-32). > Can it get any clearer? Unfortunately, in the early '80's, it appearently wasn't clear enough for compiler developers. I used multiple validated compilers during that time that didn't implement this AI. I don't expect this condition is quite as prevalent in the '90s, of course, particularly with Ada 95, but certainly there were problems with some tasking _implementations_ in the '80s, which is why applications with their roots in the 80's did not always use tasking. -- LMTAS - "Our Brand Means Quality" For more info, see http://www.lmtas.com or http://www.lmco.com