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Message-ID: <aaf68971-2a06-4be7-aeb0-1f100d628cea@lucifer.local>
Date: Mon, 13 Oct 2025 11:20:30 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Lance Yang <lance.yang@...ux.dev>
Cc: akpm@...ux-foundation.org, elver@...gle.com, Liam.Howlett@...cle.com,
david@...hat.com, harry.yoo@...cle.com, jannh@...gle.com,
linux-kernel@...r.kernel.org, linux-mm@...ck.org, riel@...riel.com,
syzkaller-bugs@...glegroups.com, vbabka@...e.cz,
syzbot+60192c8877d0bc92a92b@...kaller.appspotmail.com
Subject: Re: [PATCH 1/1] mm: silence data-race in update_hiwater_rss
On Fri, Sep 26, 2025 at 05:24:26PM +0800, Lance Yang wrote:
> From: Lance Yang <lance.yang@...ux.dev>
>
> KCSAN reports a data race on mm_cluster.hiwater_rss, which can be accessed
> concurrently from various paths like page migration and memory unmapping
> without synchronization.
>
> Since hiwater_rss is a statistical field for accounting purposes, this data
> race is benign. Annotate both the read and write accesses with data_race()
> to make KCSAN happy.
>
> Reported-by: syzbot+60192c8877d0bc92a92b@...kaller.appspotmail.com
> Closes: https://lore.kernel.org/linux-mm/68d6364e.050a0220.3390a8.000d.GAE@google.com
> Signed-off-by: Lance Yang <lance.yang@...ux.dev>
LGTM, so:
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> ---
> include/linux/mm.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 6b6c6980f46c..dd93335e3a13 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2757,7 +2757,7 @@ static inline void update_hiwater_rss(struct mm_struct *mm)
> unsigned long _rss = get_mm_rss(mm);
>
> if (data_race(mm->hiwater_rss) < _rss)
> - (mm)->hiwater_rss = _rss;
> + data_race(mm->hiwater_rss = _rss);
> }
>
> static inline void update_hiwater_vm(struct mm_struct *mm)
> --
> 2.49.0
>
>
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