Re: [PATCH 1/1] mm, oom_adj: don't loop through tasks in __set_oom_adj when not necessary

Oleg Nesterov
2020-08-21T16:38:25Z

again, don't really understand...

On 08/21, Suren Baghdasaryan wrote:
>
> Actually, reviewing again and considering where list_add_tail_rcu is
> happening, maybe the race with clone(CLONE_VM) does not introduce
> false negatives.

I think it does... Whatever we check, mm_users or MMF_PROC_SHARED,
the task can do clone(CLONE_VM) right after the check.

> However a false negative I think will happen when a
> task shares mm with another task and also has an additional thread.
> Shared mm will increment mm_users without adding to signal->live

Yes,

> and
> the additional thread will advance signal->live without adding to
> mm_users.

No, please note that CLONE_THREAD requires CLONE_VM.

Oleg.