On Tue, Jan 14, 2020 at 10:31:22AM +0100, Michal Hocko wrote: > On Sat 11-01-20 03:03:52, Kirill A. Shutemov wrote: > > On Thu, Jan 09, 2020 at 10:30:54PM +0800, Wei Yang wrote: > > > As all the other places, we grab the lock before manipulate the defer list. > > > Current implementation may face a race condition. > > > > > > For example, the potential race would be: > > > > > > CPU1 CPU2 > > > mem_cgroup_move_account split_huge_page_to_list > > > !list_empty > > > lock > > > !list_empty > > > list_del > > > unlock > > > lock > > > # !list_empty might not hold anymore > > > list_del_init > > > unlock > > > > I don't think this particular race is possible. Both parties take page > > lock before messing with deferred queue, but anytway: > > > > Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > > I am confused, if the above race is not possible then what would be a > real race? We really do not want to have a patch with a misleading > changelog, do we? The alternative is to make sure that all page_deferred_list() called with page lock taken. I'll look into it. -- Kirill A. Shutemov
