Re: [PATCH v16 3/8] cpu/hotplug: Add dynamic parallel bringup states before CPUHP_BRINGUP_CPU

David Woodhouse
2023-03-24T10:01:27Z

[-- Attachment #1: Type: text/plain, Size: 793 bytes --]

On Fri, 2023-03-24 at 10:46 +0100, Thomas Gleixner wrote:
>
> It's even worse. Any topology relevant change _must_ be serialized by
> holding cpu_hotplug_lock write locked. So this needs fundamentally more
> thought

Yes. Yes, it does. Which is why it isn't being done in parallel in this
patch series. The topology update happens from smp_callin() which
happens from do_wait_cpu_initialized(), which is still in the
CPUHP_BRINGUP_CPU stage for now, being done one at a time.

When we come to look at the next stage, doing do_wait_cpu_initialized()
in parallel for multiple APs too, we will be happy to hear specifics of
why this "must" be serialized by the cpu_hotplug_lock and no other. It
will be great to check that we haven't missed anything.

But we aren't there yet.

[-- Attachment #2: smime.p7s --]
[-- Type: application/pkcs7-signature, Size: 5965 bytes --]