linux-kernel - Re: [PATCH] mm: change memcg->oom_group access with atomic operations

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Message-ID: <Y/PhmEPc/qYeZ52T@P9FQF9L96D>
Date:   Mon, 20 Feb 2023 13:09:44 -0800
From:   Roman Gushchin <roman.gushchin@...ux.dev>
To:     Yue Zhao <findns94@...il.com>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org, hannes@...xchg.org,
        mhocko@...nel.org, shakeelb@...gle.com, muchun.song@...ux.dev,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: change memcg->oom_group access with atomic operations

On Mon, Feb 20, 2023 at 11:16:38PM +0800, Yue Zhao wrote:
> The knob for cgroup v2 memory controller: memory.oom.group
> will be read and written simultaneously by user space
> programs, thus we'd better change memcg->oom_group access
> with atomic operations to avoid concurrency problems.
> 
> Signed-off-by: Yue Zhao <findns94@...il.com>

Hi Yue!

I'm curious, have any seen any real issues which your patch is solving?
Can you, please, provide a bit more details.

Also, WRITE/READ_ONCE() don't generally make operations atomic,
they only prevent the compiler from merging and re-fetching reads
and writes.

Thanks!