Re: [PATCH v5 7/9] task_isolation: don't interrupt CPUs with tick_nohz_full_kick_cpu()

Thomas Gleixner
2020-11-23T22:37:05Z

On Mon, Nov 23 2020 at 17:58, Alex Belits wrote:
> From: Yuri Norov <ynorov@marvell.com>
>
> For nohz_full CPUs the desirable behavior is to receive interrupts
> generated by tick_nohz_full_kick_cpu(). But for hard isolation it's
> obviously not desirable because it breaks isolation.
>
> This patch adds check for it.

git grep 'This patch' Documentation/process/

> */
> void tick_nohz_full_kick_cpu(int cpu)
> {
> - if (!tick_nohz_full_cpu(cpu))
> + smp_rmb();

Undocumented smp_rmb() ...

> + if (!tick_nohz_full_cpu(cpu) || task_isolation_on_cpu(cpu))
> return;

I still have to see a convincing argument why task isolation is special
and not just a straight forward extension of NOHZ full cpu isolation.

It's not special as much as you want it to be special.

Thanks,

tglx