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Re: Hard-Realtime behaviour
- From: R Vamshi Krishna <vamshi at cse dot iitb dot ac dot in>
- To: John Carter <john dot carter at tait dot co dot nz>
- Cc: ecos-discuss at sourceware dot org
- Date: Mon, 19 Jun 2006 05:12:39 +0530 (IST)
- Subject: Re: [ECOS] Hard-Realtime behaviour
- References: <Pine.LNX.4.61.0605291751420.14208@mars.cse.iitb.ac.in><XFMail.2 0060529195143.wk-list@koebler.com> <20060530075335.GG2876@lunn.ch><69dd805e0605300109k5dcf7986of596c0b5f796c6b 4@mail.gmail.com><20060530081637.GH2876@lunn.ch><Pine.LNX.4.61.060530143151 0.22231@mars.cse.iitb.ac.in><20060530111112.GK2876@lunn.ch><Pine.LNX.4.61.0 606031953120.6382@mars.cse.iitb.ac.in><001501c6874a$10fbb9a0$070fe644@EngAt PlayWS><Pine.LNX.4.61.0606040253350.26447@mars.cse.iitb.ac.in><003401c6885d $23027ee0$070fe644@EngAtPlayWS><Pine.LNX.4.61.0606190324080.3571@mars.cse.i itb.ac.in> <Pine.LNX.4.64.0606191117470.3234@parore>
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.
Any help regarding hardening of eCos would be welcome.
On Mon, 19 Jun 2006, John Carter wrote:
On Mon, 19 Jun 2006, R Vamshi Krishna wrote:
Now this hard real-time OS would be for use in Safety-Critical Systems. We
would port the kernel to MISRA-C later stage but currently we are stuck-up
at "hardening" of eCos.
Since currently most of the kernel seems to be C++, that wouldn't be
"port", that would be "rewrite". ie. If MISRA-C for the kernel is a
fixed requirement, you have lost right there.
My mistake. I indeed did mean re-write.
This guarantee I understand cannot be given by an RTOS alone. It is the
combined guarantee by the application + RTOS. i.e. everything depends on
the way the application was developed using the features of an RTOS.
Comment 1: Ecos has met all hard deadline requirements on our app...
Getting our code to behave has been way more problematical than Ecos.
Comment 2: Given a choice of a "harder RTOS" than ecos, "misra-c"
kernel, or a faster / smarter CPU with loads of Flash/RAM, I will take
the faster smarter CPU.
Headroom and flexibility are more important than "guarantees".
Guarantees can be broken, but headroom lets you cope with any broken
guarantees and a lot more besides.
Comment 3: Most "hard to meet hard deadlines" I have seen have been the
result of
hardware designers saying "lets skimp a bit and fix it in the software".
So if you have a really hard hard to meet RT deadline, walk over to your
hardware designers and talk to them about life, the universe, safety and
trade offs.
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.
--
Regards,
Vamshi
-------------------------------------------------
R.Vamshi Krishna,
M.Tech. CSE (II year),
IIT Bombay
Room no. 320, A-wing, Hostel-12
Mobile : +919869781633
-------------------------------------------------
Yesterday is a past, tomorrow is a future , today is a gift that's why it's called 'present'
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