Re: [PATCH] timers: Exclude isolated cpus from timer migation

Gabriele Monaco
2025-04-14T08:06:14Z

On Sat, 2025-04-12 at 00:57 +0200, Frederic Weisbecker wrote:
>
> If you want housekeeping CPUs to pull timers from isolated ones, then
> you
> need isolated CPUs to eventually be part of the hierarchy (be
> "available"),
> because they would need to propagate their global timers up to the
> top.
>
> If they propagate their global timers then they must play the whole
> hierarchy
> game and be ready to pull the timers from any other CPUs.
>
> Because if they propagate their timers, they must also propagate
> their
> idle state to synchronize with the whole hierarchy and know if there
> is
> a non-idle housekeeping CPU to take care of their timers. And if they
> propagate
> their (non) idle state, the isolated CPUs also declare themselves as
> available
> to handle other's timers.
>
> And working around that would be very nasty.
>

Well, that's exactly what I was trying to do, thanks for pointing this
out. I guess I won't go down that rabbit hole then.

Thanks,
Gabriele