Re: [PATCH 1/6] mm, oom: do not loop over all tasks if there are no external tasks sharing mm

From: Michal Hocko
Date: Fri May 27 2016 - 03:15:32 EST

On Fri 27-05-16 08:45:10, Michal Hocko wrote:
> It is still an operation which is not needed for 99% of situations. So
> if we do not need it for correctness then I do not think this is worth
> bothering.

Since you have pointed out exit_mm vs. __exit_signal race yesterday I
was thinking how to make the check reliable. Even
atomic_read(mm->mm_users) > get_nr_threads() is not reliable and we can
miss other tasks just because the current thread group is mostly past
exit_mm. So far I couldn't find a way to tweak this around though.
I will think about it more but I am afraid that a flag would be really
needed afterall.
Michal Hocko