Re: [PATCH] mm,memory_hotplug: Drop unneeded locking

[Oscar Salvador]

On Tue, Jun 01, 2021 at 11:47:13AM +0200, Michal Hocko wrote:
> While you are touching this and want to drill all the way down then it
> would be reasonable to drop pgdat resize locks as well.
> It is only used in the early boot code and we have one executing thread
> context per numa node during the deferred initialization. I haven't
> checked all potential side effects the lock might have but it sounds
> like there is quite some clean up potential over there.

I am not sure about that. True is that deferred_init_memmap() gets executed
on numa-thread so it's not a problem for itself, but we also have deferred_grow_zone().
It might be that while deferred_init_memmap() is running, we also have calls to
deferred_grow_zone() for the same node and that would cause some trouble wrt.
first_deferred_pfn. I need to double check it, but IIRC, that is the case.


-- 
Oscar Salvador
SUSE L3