Re: [RFC PATCH] mm: thp: grab the lock before manipulation defer list

[Wei Yang]

On Mon, Jan 06, 2020 at 11:23:45AM +0100, Michal Hocko wrote:
>On Fri 03-01-20 22:34:07, Wei Yang wrote:
>> As all the other places, we grab the lock before manipulate the defer list.
>> Current implementation may face a race condition.
>
>Please always make sure to describe the effect of the change. Why a racy
>list_empty check matters?
>

Hmm... access the list without proper lock leads to many bad behaviors.

For example, if we grab the lock after checking list_empty, the page may
already be removed from list in split_huge_page_list. And then list_del_init
would trigger bug.

-- 
Wei Yang
Help you, Help me