Re: [gentoo-embedded] Hard Real Time Systems with Gentoo?

[wireless]

not.
Bob Paddock wrote:

> The way I posed the question was meant to result in:

> "Yes, there is a RTOS that works well with Gentoo-Embedded,
> and it is XYZ at http...."
>
> How would you have asked the question?


I think you just did. You seem to be very versed
in the RTOS offerings, commercial or opensource.
Notice the name RTOS, it does not differential
between soft and hard. When it all boils down to the essence,
that distinction is meaningless. What the should be called
is reliable, low-latency executive. But everybody
accepts the moniker RTOS as OS for embedded systems.
RTOS do not have State Machine semantics, unless the
firmware engineer that using the RTOS imposes that
rigidly in the software design. The RTOS might have
available mechanisms and resources for the firmware
engineer to create a state machine, using their RTOS,
but it's not ensured, just by selecting a given RTOS.


>> Soft real time, means that timing constraints are soft
>> or guildlines for process performance metrics.

> Erlang is a 'Soft' Real Time System, not what I need at the moment.

>> Hard real time, means the timing constraints are hard
>> or an absolute requirement.

> I am aware of the issues, that is why I made the distinction,
> in what I was after.

>> to not be 'real time'. But think about if a missile,
>> is suppose to change it's rudder in response to an
>> AD input, in 150ns, does it mean that the missile   as
>> as system is a failure if the rudder response is
>> 151 ns or 150.002 ns?

> If it is in the targeting system, it makes the difference between
> hitting the target or not.  A 1 ns difference, is a large
> area to transverse when your missile is traveling at Mach-6.
> A missed target is a failed Missile System.

possibly, possible not.


> TechUpdate from the Missile Defense Agency
> comes out quarterly.  MDA funds a lot of research in other
> areas.   The Summer 2006 laying here beside me is
> about "Phasing out Brest Cancer" using Microwaves.
> "Fuzzy-logic software" on page ten might be more relevant to this
> list.  Check it out at: http://www.mdatechnology.net/
> Maybe someone can make a ebuild for their screen saver?

Yes many of those publications and organizations participate
in promulgation of pop-science. However, that does not
affect the reality of mathematics but it does taint the use
of precise language constructs used in math, science and engineering.

I guess if Webster's includes a word from Eubonics into the
English dictionary it becomes acceptable English?


>> Determinism is another funny character. Real embedded
>> systems use a 'state machine' design where every
>> state or transition is fully characterized and defined.

>> ON a large complex system, it is virtually impossible to
>> discover, characterize, define and test all possible states
>> of a complex system.

> Use the appropriate tools and languages such as Esterel.
> http://www.esterel-technologies.com/

Or state machine design and native assembler or ansi C.
If either system meets the (arbitrarily set timing constraints
both are classified as RT..... by the masses of pop-science.

What happens when after months of deployment a failure
in the OO dev tools appears?  Not very common with
a tested state machine design, but too often common when
OO tools are used.

>> Embedded linux anything, currently, can never be fully deterministic.
> Embedded Linux can be run as a task of a fully deterministic RTOS,
> built with a Finite State Machine if you like.


Are you kidding?   Deterministic means all possible state/transitions
have been defined, tested and verified. Do you really think that
has ever been accomplished on any Unix/Linux system?

Nasa did it decades ago on a processor and spent so much time
and money that it has never been attempted again, except as
pop-science projects using magic and pop-statistical models.

> Any done with Gentoo-Embedded?

Nope and never with any Unix/linux/bsd operation system.
However, Bill Gates will probable tell you that windowXP
has this feature (again pop-science).

> I know what I'm building, as well as being well aware of the high
> importance of System Design Requirements.
> But will I find one that actually answered my question?  :-)

If you ask a question with common mathematical misconceptions,
some may point out the invalid requests. And no you did not
ask for RTOS options, you asked for
"Does anyone know of any Hard Real Time Systems,
where deterministic response is required, that work
with Gentoo-Embedded?"

Although RTOS is a common term, it does not ensure HRT performance,
but, the user accepts 'best effort' reliable, timing constraints
when using an RTOS embedded operating systems. If others want
to incorrectly use terms such as hard and soft real time,
then it's either pop-science or marketing; you pick.

(Fully) Deterministic systems are an enormous level above HRT and
rarely exist except in smaller systems. The very nature of a uinx
OS (embedded or not) is gargantuan when you look at the possible
number of states and transitions.


James




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