Re: [PATCH v2 1/2] cpu/hotplug: introduce 'num_dying_cpus' to get dying CPUs count

[Thomas Gleixner]

On Thu, Apr 06 2023 at 09:56, Ye Bin wrote:
> From: Ye Bin <yebin10@xxxxxxxxxx>
>
> Introduce '__num_dying_cpus' variable to cache the number of dying CPUs
> in the core and just return the cached variable.

Why?

That atomic counter is racy too if read and acted upon w/o having CPUs
read locked.

All it does is making the race window smaller vs. the cpumask_weight()
based implementation. It's still racy and incorrect.

So no, this is not going to happen.

Thanks,

        tglx