[RFC 2/3] kernel/cpu: Mark nonboot cpus as inactive when shutting down nonboot cpus

[Thomas Gleixner]

On Tue, Oct 28 2025 at 10:51, Pingfan Liu wrote:
> On Mon, Oct 27, 2025 at 06:06:32PM +0100, Thomas Gleixner wrote:
>> When kexec() is in progress, then running user space tasks at all is a
>> completely pointless exercise.
>> 
>> So the obvious solution to the problem is to freeze all user space tasks
>
> I agree, but what about a less intrusive approach? Simply stopping the 
> DL tasks should suffice, as everything works correctly without them.

What's intrusive about that? Task freezing exists already.

> I have a draft patch ready. Let's discuss it and go from there.
>
>> when kexec() is invoked. No horrible hacks in the deadline scheduler and
>> elsewhere required to make that work. No?
>
> To clarify, skipping the dl_bw_deactivate() validation is necessary 
> because it prevents CPU hot-removal.

If you freeze stuff there is nothing to do. Hibernation works exactly
that way without any magic hacks in a particular scheduling class, no?

Thanks,

        tglx