Re: [PATCH v2 3/3] drivers/base/memory: fix locking for poison accounting lookup

["David Hildenbrand (Arm)" <david@kernel.org>]

On 4/29/26 12:11, Usama Arif wrote:
> On Wed, 29 Apr 2026 12:18:08 +0800 Muchun Song <muchun.song@linux.dev> wrote:
> 
>>
>>
>>>
>>>
>>> lock_device_hotplug is a mutex lock, and we already take other mutex locks while
>>> holding lock_folio in other paths, so I am not sure I see what should be special
>>> in this case.
>>
>> Hi Oscar and Miaohe,
>>
>> I saw sashiko's report [1] related to folio lock and lock_device_hotplug.
>> Seems it is possible. You can correct me if I am wrong.
>>
>> [1] https://sashiko.dev/#/patchset/20260428085219.1316047-1-songmuchun%40bytedance.com
>>
>> We could fix this by calling action_result() without holding folio lock.
>> What do you think?
>>
> 
> Hello Muchun,
> 
> You could end up in memblk_nr_poison_sub() while holding hugetlb_lock spin lock
> from get_huge_page_for_hwpoison(), right?
> 
> Lockdep would flag this as sleeping while atomic when acquiring mutex I think.

Another thought would be, that we always call the inc/sub from memory failure
code while we hold a folio reference and the page is not poisoned yet.

That way, memory offlining cannot continue and the memory block cannot go away.

So we'd let out page reference keep the memory block alive.

-- 
Cheers,

David