Re: [PATCH 3/5] sched: Enable PREEMPT_DYNAMIC for PREEMPT_RT

[Peter Zijlstra]

On Wed, Oct 09, 2024 at 11:52:36PM -0700, Christoph Hellwig wrote:
> On Mon, Oct 07, 2024 at 09:46:12AM +0200, Peter Zijlstra wrote:
> > In order to enable PREEMPT_DYNAMIC for PREEMPT_RT, remove PREEMPT_RT
> > from the 'Preemption Model' choice. Strictly speaking PREEMPT_RT is
> > not a change in how preemption works, but rather it makes a ton more
> > code preemptible.
> > 
> > Notably, take away NONE and VOLATILE options for PREEMPT_RT, they make
> > no sense (but are techincally possible).
> 
> Should we take away NONE entirely because it is kinda silly?
> 
> Just a bystander here, but the explosion of different preemption models
> is a bit silly and not really helpful to users.

The end goal is to get rid of Voluntary and None, but getting there will
require more work. A lot of careful work to be sure. In the end we
should be rid of those two preemption models and the cond_resched() and
much of the random need_resched() hackery they brought.

But we can't do it all at once, so yeah, we need to grow extra crap
before we can take out the old stuff. Nothing new there, but I get your
frustration.