From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 29141 invoked by alias); 19 Jun 2006 00:27:33 -0000 Received: (qmail 29129 invoked by uid 22791); 19 Jun 2006 00:27:32 -0000 X-Spam-Check-By: sourceware.org Received: from gatekeeper.tait.co.nz (HELO gatekeeper.tait.co.nz) (202.37.96.11) by sourceware.org (qpsmtpd/0.31) with ESMTP; Mon, 19 Jun 2006 00:27:29 +0000 Received: from gatekeeper.tait.co.nz (localhost.localdomain [127.0.0.1]) by localhost.tait.co.nz (Postfix) with ESMTP id A31DF46757 for ; Mon, 19 Jun 2006 12:27:26 +1200 (NZST) Received: from sunstrike.tait.co.nz (sunstrike [172.25.40.92])by gatekeeper.tait.co.nz (Postfix) with ESMTP id 92CB846749for ; Mon, 19 Jun 2006 12:27:26 +1200 (NZST) Received: from conversion-daemon.sunstrike.tait.co.nz by sunstrike.tait.co.nz(Sun Java System Messaging Server 6.1 (built Apr 28 2004))id <0J1200901W4VSG00@sunstrike.tait.co.nz>(original mail from john.carter@tait.co.nz) for ecos-discuss@sourceware.org;Mon, 19 Jun 2006 12:27:26 +1200 (NZST) Received: from parore ([172.25.140.12])by sunstrike.tait.co.nz (Sun Java System Messaging Server 6.1 (built Apr 282004)) with ESMTP id <0J12006IHZXOSR70@sunstrike.tait.co.nz>; Mon,19 Jun 2006 12:27:24 +1200 (NZST) Received: from localhost ([127.0.0.1] ident=johnc)by parore with esmtp (Exim 4.34) id 1Fs7bw-0001gh-7M; Mon,19 Jun 2006 12:27:24 +1200 Date: Mon, 19 Jun 2006 00:27:00 -0000 From: John Carter In-reply-to: To: R Vamshi Krishna Cc: ecos-discuss@sourceware.org Message-id: MIME-version: 1.0 X-Mailer: Pidgeon Post Content-type: TEXT/PLAIN; format=flowed; charset=US-ASCII Content-transfer-encoding: 7BIT X-Apparently-From: mars X-Contents: May contain traces of nuts. References: <"XFMail. 2 0060529195143.wk-list"@koebler.com> <20060530075335.GG2876@lunn.ch><"69dd805e0605300109k5dcf7986of596c0b5f796c6 b 4"@mail.gmail.com><20060530081637.GH2876@lunn.ch><"Pine.LNX.4.61.0605301431 51 0.22231"@mars.cse.iitb.ac.in><20060530111112.GK2876@lunn.ch><"Pine.LNX.4.61 .0 606031953120.6382"@mars.cse.iitb.ac.in><"003401c6885d $23027ee0$070fe644"@EngAtPlayWS>

X-imss-version: 2.040 X-imss-result: Passed X-imss-approveListMatch: *@tait.co.nz X-IsSubscribed: yes 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 Subject: Re: [ECOS] Hard-Realtime behaviour X-SW-Source: 2006-06/txt/msg00160.txt.bz2 On Mon, 19 Jun 2006, R Vamshi Krishna wrote: > Thank you for the reply. But the fact remains that we would like to have a > "Hard" real-time OS irrespective of the processor/speed and ram/rom. Let me give you a concrete, real life, happened several times, example. If say some dumb user level code, in a non-safety critical part of your code does a timer call back. And in the call back calls some other code, that calls some other code that does a wait of some form. Since the timer call back is in an ecos DSR context, even though ecos kernel is entirely well behaved, your user code will cause the kernel to lock up until the wait is over. Not the kernel's fault, ecos did exactly what was asked according to spec. However, all kinds of even pretty soft deadlines got missed. 99% of the code in a usual app does not, should not have hard RT deadlines. (If they do, you are designing it wrong!) But in an RTOS like ecos, that 99% of the code can trivially screw up the deadlines of the 1% time critical code. Suggestion: If it is really "safety critical", use embedded linux with a MMU and processes not threads. PS: If your project is just a very very thin smear of code that can be wired direct to the hardware interrupts and doesn't need threads and schedulers and mutexs and mailboxes etc, ignore the next paragraph. If your project is seriously planning on "rewriting" an RTOS semi-from scratch for your App just for the supposed benefit of MISRA_C.... This project you are on is a one-way ticket to deathmarch hell. John Carter Phone : (64)(3) 358 6639 Tait Electronics Fax : (64)(3) 359 4632 PO Box 1645 Christchurch Email : john.carter@tait.co.nz New Zealand Carter's Clarification of Murphy's Law. "Things only ever go right so that they may go more spectacularly wrong later." >From this principle, all of life and physics may be deduced. -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss