Re: [RFC PATCH RT v2 1/2] time/hrtimer: Add PINNED_HARD mode for realtime hrtimers

[Juri Lelli]

Hi,

On 19/06/21 09:56, Thomas Gleixner wrote:
> On Sat, Jun 19 2021 at 01:35, Thomas Gleixner wrote:
> > The wild west of anything which scratches 'my itch' based on 'my use
> > case numbers' in Linux ended many years ago and while RT was always a
> > valuable playground for unthinkable ideas we definitely tried hard not
> > to accept use case specific hacks wihtout a proper justification that it
> > makes sense in general.
> >
> > So why are you even trying to sell this to me?
> 
> I wouldn't have been that grumpy if you'd at least checked whether the
> task is pinned. Still I would have told you that you "fix" it at the
> wrong place.

Ah, indeed. Pulled the trigger too early it seems. I'll ponder more.

> Why on earth is that nohz heuristic trainwreck not even checking that?
> It's not a RT problem and it's not a problem restricted to RT tasks
> either. If a task is pinned then arming the timer on a random other CPU
> is blatant nonsense independent of the scheduling class.

Agree. Lemme look more into it.

Thanks for the comments!

Best,
Juri