linux-kernel - Re: [PATCH] mm, memcg: prevent missed memory.low load tears

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Message-ID: <20200615064219.GA25296@dhcp22.suse.cz>
Date:   Mon, 15 Jun 2020 08:42:19 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Chris Down <chris@...isdown.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Michal Koutný <mkoutny@...e.com>
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 Koutný <mkoutny@...e.com>
> Signed-off-by: Chris Down <chris@...isdown.name>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  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