linux-kernel - Re: [PATCH] mm: don't rely on system state to detect hot-plug operations

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Date:   Wed, 9 Sep 2020 11:24:24 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Laurent Dufour <ldufour@...ux.ibm.com>,
        Michal Hocko <mhocko@...e.com>
Cc:     akpm@...ux-foundation.org, Oscar Salvador <osalvador@...e.de>,
        rafael@...nel.org, nathanl@...ux.ibm.com, cheloha@...ux.ibm.com,
        stable@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: don't rely on system state to detect hot-plug
 operations

>> I am not sure an enum is going to make the existing situation less
>> messy. Sure we somehow have to distinguish boot init and runtime hotplug
>> because they have different constrains. I am arguing that a) we should
>> have a consistent way to check for those and b) we shouldn't blow up
>> easily just because sysfs infrastructure has failed to initialize.
> 
> For the point a, using the enum allows to know in register_mem_sect_under_node() 
> if the link operation is due to a hotplug operation or done at boot time.
> 
> For the point b, one option would be ignore the link error in the case the link 
> is already existing, but that BUG_ON() had the benefit to highlight the root issue.
> 

WARN_ON_ONCE() would be preferred  - not crash the system but still
highlight the issue.

> Cheers,
> Laurent.
> 


-- 
Thanks,

David / dhildenb