[ECOS] Hard-Realtime behaviour

R Vamshi Krishna vamshi@cse.iitb.ac.in
Sun Jun 18 23:46:00 GMT 2006

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.


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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