On Mon, Aug 02, 1999 at 09:45:38AM -0400, Dresner, Norman A. wrote:
> Obviously we can translate the ISR's directly into device drivers and the
> display tasks into "normal" UNIX prioritized tasks, but what's the best way
> to handle what are the currently prioritized message and hardware-handling
> tasks? We can't guarantee timely completion every time because the running
> time is (partially) data-dependent, but we know from years of experience
> that on the average we're >99% timely completion. We do feel that we'd like
> to maintain the prioritized nature of these tasks Is there any way within
> RTLinux to prioritize real-time tasks?
RTLinux tassk are prioritized and the scheduler uses the priorities
to pick which task to run next.
So, the answer is, it's trivial.
>
> Norm
>
> > -----Original Message-----
> >
> > Avoid the use of priority if at all possible, and if needed use it as
> > little as possible. Instead, have your tasks designed so they have
> > well defined completion time bounds (or time bounds for time to yield
> > the CPU to other tasks).
> >
> > One of the nasty ways systems can fail is that they work fine until
> > presented with a very high load, at which point critical things don't
> > get done anymore because other things were given higher priority and
> > they now consume 100% of the CPU. If you don't use priority and your
> > tasks all have time bounds, this failure cannot happen, and your
> > system is stable under all loads.
> >
> > To put it differently: if you use priority, it is far harder to prove
> > liveness and time bounds for any tasks other than the subset that uses
> > the highest priority. (And if you use interrupts, it gets even
> > harder.)
> >
> >
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