Re: Memory hotplug softlock issue

[Vlastimil Babka]

On 11/19/18 5:46 PM, Vlastimil Babka wrote:
> On 11/19/18 5:46 PM, Michal Hocko wrote:
>> On Mon 19-11-18 17:36:21, Vlastimil Babka wrote:
>>>
>>> So what protects us from locking a page whose refcount dropped to zero?
>>> and is being freed? The checks in freeing path won't be happy about a
>>> stray lock.
>>
>> Nothing really prevents that. But does it matter. The worst that might
>> happen is that we lock a freed or reused page. Who would complain?
> 
> free_pages_check() for example
> 
> PAGE_FLAGS_CHECK_AT_FREE includes PG_locked

And besides... what about the last page being offlined and then the
whole struct page's part of vmemmap destroyed as the node goes away?