Re: [PATCH v2 2/5] preempt/dynamic: Introduce preempt mode accessors

On 11/11/21 11:32, Mike Galbraith wrote:

On Thu, 2021-11-11 at 10:36 +0100, Marco Elver wrote:

quoted

I guess the question is if is_preempt_full() should be true also if
is_preempt_rt() is true?

That's what CONFIG_PREEMPTION is.  More could follow, but it was added
to allow multiple models to say "preemptible".

That's what I was gonna say, but you can have CONFIG_PREEMPTION while being
is_preempt_none() due to PREEMPT_DYNAMIC...

quoted

Not sure all cases are happy with that, e.g. the kernel/trace/trace.c
case, which wants to print the precise preemption level.

Yeah, that's the "annoying" bit, needing one oddball model accessor
that isn't about a particular model.

quoted

To avoid confusion, I'd introduce another helper that says true if the
preemption level is "at least full", currently that'd be "full or rt".
Something like is_preempt_full_or_rt() (but might as well write
"is_preempt_full() || is_preempt_rt()"), or is_preemption() (to match
that Kconfig variable, although it's slightly confusing). The
implementation of that helper can just be a static inline function
returning "is_preempt_full() || is_preempt_rt()".

Would that help?

Yeah, as it sits two accessors are needed, one that says PREEMPT the
other PREEMPTION, spelling optional.

Per the above, I think we need the full || rt thingie.

      -Mike