Hi Steven,
I don't know what a "long" deadline is ... is is something like this:
http://harolds-planet.blogspot.com/2006/02/how-to-deal-with-deadlines.html
Cheers
--Armin
PS: I think you mean a time range where results are treated as delivered
timely ?
Steven Rostedt wrote:
On Thu, 2010-09-16 at 08:27 -0700, Nivedita Singhvi wrote:
Steven Rostedt wrote:
Hardware that is less complex is easier to mathematically prove that it
will do what you expect to do in all cases, than hardware that is over
engineered, just like software.
I hold that PREEMPT_RT is not soft real time, but is hard real time
designed. That is, we can't prove that it is hard real time, but any
time we find a case that the software can break its deterministic
result, it is a bug and needs to be fixed. (aka, a system failure).
Which serves to highlight my point about using these terms -- you're
the terms "hard" and "soft" in a different way than a previous poster.
(Assuming "hard real time designed" can get mistaken for "hard real time".
Hard and soft are relative terms.
You're saying it's hard because we intend it to meet system deadlines
(regardless of deadline??), and it's a bug if it doesn't.
heh, no. The "regardless of deadlines" was not what I meant. I meant "we
have determined that the worse case runtime is X+delta, and if we run
within that time the system works". The deadlines are determined at
system design based on the hardware and software used. If you can not
make a deadline at design time, you go back to the drawing board.
It's all about determinism.
The previous poster in this list was using it to imply guarantees of
of very specific response times (< xxx us).
You really, really have to talk about the specifics of the environment,
the requirements, the application needs, etc. And I'm missing about
half a dozen "really"'s there.
Note, I'm not sure you implied that vanilla Linux being fast enough can
be considered "real-time" for long deadlines. If that's the case, it is
wrong. A simple classic case of priority inversion will cause the system
to fail no matter how long the deadlines are.
-- Steve
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