From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15688 invoked by alias); 24 Jun 2005 19:52:12 -0000 Mailing-List: contact ecos-discuss-help@ecos.sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: ecos-discuss-owner@ecos.sourceware.org Received: (qmail 15654 invoked by uid 22791); 24 Jun 2005 19:52:07 -0000 Received: from nproxy.gmail.com (HELO nproxy.gmail.com) (64.233.182.194) by sourceware.org (qpsmtpd/0.30-dev) with ESMTP; Fri, 24 Jun 2005 19:52:07 +0000 Received: by nproxy.gmail.com with SMTP id d4so103977nfe for ; Fri, 24 Jun 2005 12:52:04 -0700 (PDT) Received: by 10.48.4.20 with SMTP id 20mr66854nfd; Fri, 24 Jun 2005 12:52:04 -0700 (PDT) Received: by 10.48.43.13 with HTTP; Fri, 24 Jun 2005 12:52:04 -0700 (PDT) Message-ID: <69dd805e050624125228f3b7c0@mail.gmail.com> Date: Fri, 24 Jun 2005 19:52:00 -0000 From: Fabian Scheler Reply-To: Fabian Scheler To: R Vamshi Krishna Cc: ecos-discuss@sources.redhat.com In-Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline References: Subject: Re: [ECOS]: Is eCos Hard Real Time OS ?? X-SW-Source: 2005-06/txt/msg00254.txt.bz2 Hi, I somehow have the feeling, that you have a somehow strange opinion about what you call "hard real time systems", so what is a hard real time system? Well, the general understanding of a hard real time systems is that is has to fulfill some tasks which underlie hard timing constraints called deadlines. These deadlines must be guaranteed under all circumstances otherwise the whole system fails. But these tasks (these tasks do not directly correspond to threads or processes!) are part of the whole real time system, t.m. of an application, an operating system just provides an infrastructure to execute this application. Deadlines now have to be guaranteed within the application, not within the operating system, as these deadlines are application specific! How should an operating system guarantee the deadline of such a task? You have to analyze the whole application and make sure that every task completes in time by some kind of formal technique (WCET, scheduling theory ...). The most important property of an RTOS is determinism, so you can such formal techniques and verify your system. OK, some operating systems do not provide an infrastructure that is suitable for building real time systems,of course (eg. Windows, Linux ...), but eCos does. At least: they way you are describing your requirements seems like you are going to build a time triggered real time system, maybe eCos is not the best choice here. eCos is better for designing event triggered systems. Ciao, Fabian -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss