Re: [PATCH 4/4] cpu/hotplug: Fix CPU down rollback

[Peter Zijlstra]

On Mon, Jan 11, 2021 at 05:10:47PM +0000, vincent.donnefort@xxxxxxx wrote:
> From: Vincent Donnefort <vincent.donnefort@xxxxxxx>
> 
> After the AP brought itself down to CPUHP_TEARDOWN_CPU, the BP will finish
> the job. The steps left are as followed:
> 
>    +--------------------+
>    | CPUHP_TEARDOWN_CPU |  -> If fails state is CPUHP_TEARDOWN_CPU
>    +--------------------+
>    |   ATOMIC STATES    |  -> Cannot Fail
>    +--------------------+
>    |  CPUHP_BRINGUP_CPU |  -> Cannot fail
>    +--------------------+
>    |        ...         |
>    |        ...         |  -> Can fail and rollback

These are the PREPARE/DEAD states, right? It would be _really_ daft for
a DEAD notifier to fail. But yeah, I suppose that if it does, it will
indeed end up in CPUHP_AP_ONLINE_IDLE.

Do we want to WARN when a DEAD notifier fails?