linux-kernel - Re: [PATCH linux-next] mm/huge_memory: mark racy access on huge_anon_orders

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Date: Mon, 13 May 2024 13:05:28 -0600
From: Yang Shi <shy828301@...il.com>
To: xu.xin16@....com.cn
Cc: akpm@...ux-foundation.org, david@...hat.com, willy@...radead.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, ziy@...dia.com
Subject: Re:  [PATCH linux-next] mm/huge_memory: mark racy access on huge_anon_orders_always

On Sat, May 11, 2024 at 12:44 AM <xu.xin16@....com.cn> wrote:
>
> From: Ran Xiaokai <ran.xiaokai@....com.cn>
>
> huge_anon_orders_always and huge_anon_orders_always are accessed
> lockless, it is better to use the READ_ONCE() wrapper.
> This is not fixing any visible bug, hopefully this can cease some
> KCSAN complains in the future.

A little bit confused here. Did you see complaints from KCSAN?

> Also do that for huge_anon_orders_madvise.
>
> Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>
> ---
>  include/linux/huge_mm.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index de0c89105076..6573430ea600 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -122,8 +122,8 @@ static inline bool hugepage_flags_enabled(void)
>          * So we don't need to look at huge_anon_orders_inherit.
>          */
>         return hugepage_global_enabled() ||
> -              huge_anon_orders_always ||
> -              huge_anon_orders_madvise;
> +                       READ_ONCE(huge_anon_orders_always) ||
> +                       READ_ONCE(huge_anon_orders_madvise);
>  }
>
>  static inline int highest_order(unsigned long orders)
> --
> 2.15.2