Re: [PATCH v3] mm: memcontrol: reword obsolete comment of mem_cgroup_unmark_under_oom()

[Michal Hocko]

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 
> Cc: Johannes Weiner 
> Cc: Michal Hocko 
> Cc: Vladimir Davydov 

Acked-by: Michal Hocko 

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

[PATCH v3] mm: memcontrol: reword obsolete comment of mem_cgroup_unmark_under_oom()

[Miaohe Lin]

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 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Vladimir Davydov 
---
 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