Re: RT patch acceptance

Andrea Arcangeli
2005-05-31T17:54:55Z

On Tue, May 31, 2005 at 01:42:59PM -0400, Steven Rostedt wrote:
> How does one demonstrate that something works without a test. You may
> call it a "demo", but in reality it is just another test. It's been
> quite some time since I use to work on that, and I never read the
> MilSpec myself, I was just told what to do by those that did read it.
> But I would still call it testing. Every requirement must have a way to
> prove that it was fulfilled, whether it was by "demo", inspection, or
> measurement, I would call all those tests.

With testing I meant to run the OS on the bare hardware in the
final configuration and verifying that it works (possibly by measuring
the worst case latencies you get during the testing, like what Ingo does
to claim worst case latency for preempt-RT).

> One of the tests that were done was to inspect ever module (or function)
> for every code path it took. This grows exponential with every branch.

Yes, that's what I meant.

> the integration level, and system level. Could you imagine what it
> would take to do this with Linux! Linux is much bigger than that code
> that ran the engine of an aircraft, and that testing took ten years!

Indeed, that's why I believe hard-RT with preempt-RT is just a joke.

> Not to mention that Linux is a moving target, and the engine control
> code was designed for a single purpose and a single type of hardware.

Exactly.

> Before I put my hand under that saw, I would want to test it several
> times with a hotdog first!

;)