On Wed 30-09-20 05:53:36, Miaohe Lin wrote:
> Since commit 79dfdaccd1d5 ("memcg: make oom_lock 0 and 1 based rather than
> counter"), the mem_cgroup_unmark_under_oom() is added and the comment of
> the mem_cgroup_oom_unlock() is moved here. But this comment make no sense
> here because mem_cgroup_oom_lock() does not operate on under_oom field. So
> we reword the comment as this would be helpful.
> [Thanks Michal Hocko for rewording this comment.]
>
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Thanks!
> ---
> mm/memcontrol.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 6877c765b8d0..4f0c14cb8690 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1817,8 +1817,8 @@ static void mem_cgroup_unmark_under_oom(struct mem_cgroup *memcg)
> struct mem_cgroup *iter;
>
> /*
> - * When a new child is created while the hierarchy is under oom,
> - * mem_cgroup_oom_lock() may not be called. Watch for underflow.
> + * Be careful about under_oom underflows becase a child memcg
> + * could have been added after mem_cgroup_mark_under_oom.
> */
> spin_lock(&memcg_oom_lock);
> for_each_mem_cgroup_tree(iter, memcg)
> --
> 2.19.1
--
Michal Hocko
SUSE Labs
