Re: PREEMPT_RT support

[Bruce Ashfield <bruce.ashfield@windriver.com>]

On 10-12-06 6:06 PM, Darren Hart wrote:
> I'm looking at how to best support PREEMPT_RT. We have a few things in
> the works which prevent the ideal scenario (which is just a new recipe
> using the preempt_rt branch in linux-yocto).
>
> 2.6.34 never had an -rt patch. The WR folks created one that builds and
> is undergoing review from tglx - but that doesn't appear to be near the
> top of his stack. 2.6.37 is still pending an -rt patch, also blocked on
> -tglx.

We'll be doing one at WR eventually, so it will exist in
one form or another for version > 2.6.34.

>
> I'm thinking of creating a meta-rt layer which would provide a latest
> -rt kernel and the rt-tests suite along with a non-graphical image
> definition that facilitates latency detection and rt performance
> measurement. poky-image-rt-test or something along those lines.
>
> Any objection to this approach? As we will eventually move these recipes
> into the core poky recipes, I'd suggest we put this in an
> "experimental/meta_rt" git repository.

I'm worrying about this muddying the water with respect to the
-rt branches in the linux-yocto repositories. In particular if
we go *backward* from the 2.6.34 variant that we already have
(remember, that -rt kernel has been heavily abused for 9
months now and is just as stable (probably more so for
non-x86) as anything else you'll find).

Why can't we continue to consolidate these into fewer kernels
and recipes ? We can't share fixes and BSPs easily if everything
is kept separate. We can obviously pair the tests/utilities along
with the linux-yocto -rt branches, so I'd prefer that approach
and continue to work on improving the base that we already
have.

Cheers,

Bruce

>
> Thoughts?
>