2020-06-12 17:49:20

by Chris Down

Subject: [PATCH] mm, memcg: prevent missed memory.low load tears

Looks like one of these got missed when massaging in f86b810c2610 ("mm,
memcg: prevent memory.low load/store tearing") with other linux-mm
changes.

Reported-by: Michal Koutn? <[email protected]>
Signed-off-by: Chris Down <[email protected]>
---
mm/memcontrol.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0b38b6ad547d..f7cc66a80348 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6416,7 +6416,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,

if (parent == root) {
memcg->memory.emin = READ_ONCE(memcg->memory.min);
- memcg->memory.elow = memcg->memory.low;
+ memcg->memory.elow = READ_ONCE(memcg->memory.low);
goto out;
}

@@ -6428,7 +6428,8 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
atomic_long_read(&parent->memory.children_min_usage)));

WRITE_ONCE(memcg->memory.elow, effective_protection(usage, parent_usage,
- memcg->memory.low, READ_ONCE(parent->memory.elow),
+ READ_ONCE(memcg->memory.low),
+ READ_ONCE(parent->memory.elow),
atomic_long_read(&parent->memory.children_low_usage)));

out:
--
2.27.0

2020-06-15 06:47:30

by Michal Hocko

Subject: Re: [PATCH] mm, memcg: prevent missed memory.low load tears

On Fri 12-06-20 18:44:37, Chris Down wrote:
> Looks like one of these got missed when massaging in f86b810c2610 ("mm,
> memcg: prevent memory.low load/store tearing") with other linux-mm
> changes.
>
> Reported-by: Michal Koutn? <[email protected]>
> Signed-off-by: Chris Down <[email protected]>

Acked-by: Michal Hocko <[email protected]>

> ---
> mm/memcontrol.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 0b38b6ad547d..f7cc66a80348 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -6416,7 +6416,7 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
>
> if (parent == root) {
> memcg->memory.emin = READ_ONCE(memcg->memory.min);
> - memcg->memory.elow = memcg->memory.low;
> + memcg->memory.elow = READ_ONCE(memcg->memory.low);
> goto out;
> }
>
> @@ -6428,7 +6428,8 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root,
> atomic_long_read(&parent->memory.children_min_usage)));
>
> WRITE_ONCE(memcg->memory.elow, effective_protection(usage, parent_usage,
> - memcg->memory.low, READ_ONCE(parent->memory.elow),
> + READ_ONCE(memcg->memory.low),
> + READ_ONCE(parent->memory.elow),
> atomic_long_read(&parent->memory.children_low_usage)));
>
> out:
> --
> 2.27.0
>

--
Michal Hocko
SUSE Labs