linux-kernel - Re: [PATCH] mm/slub: Refactor note_cmpxchg

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Message-ID: <aL6WTrXczZJYUoGb@hyeyoo>
Date: Mon, 8 Sep 2025 17:39:42 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Ye Liu <ye.liu@...ux.dev>
Cc: Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>, Ye Liu <liuye@...inos.cn>,
        Christoph Lameter <cl@...two.org>,
        David Rientjes <rientjes@...gle.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/slub: Refactor note_cmpxchg_failure for better
 readability

On Mon, Sep 08, 2025 at 03:19:21PM +0800, Ye Liu wrote:
> From: Ye Liu <liuye@...inos.cn>
> 
> Use IS_ENABLED() and standard if-else to make the code clearer.
> 
> Signed-off-by: Ye Liu <liuye@...inos.cn>
> ---

Looks good to me,
Reviewed-by: Harry Yoo <harry.yoo@...cle.com>

with a nit,

>  mm/slub.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 30003763d224..34853c0441a6 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -3064,18 +3064,16 @@ static inline void note_cmpxchg_failure(const char *n,
>  
>  	pr_info("%s %s: cmpxchg redo ", n, s->name);
>  
> -#ifdef CONFIG_PREEMPTION
> -	if (tid_to_cpu(tid) != tid_to_cpu(actual_tid))
> +	if (IS_ENABLED(CONFIG_PREEMPTION) && tid_to_cpu(tid) != tid_to_cpu(actual_tid)) {

nit: insert newline after && as it's more than 80 columns?

>  		pr_warn("due to cpu change %d -> %d\n",
>  			tid_to_cpu(tid), tid_to_cpu(actual_tid));
> -	else
> -#endif
> -	if (tid_to_event(tid) != tid_to_event(actual_tid))
> +	} else if (tid_to_event(tid) != tid_to_event(actual_tid)) {
>  		pr_warn("due to cpu running other code. Event %ld->%ld\n",
>  			tid_to_event(tid), tid_to_event(actual_tid));
> -	else
> +	} else {
>  		pr_warn("for unknown reason: actual=%lx was=%lx target=%lx\n",
>  			actual_tid, tid, next_tid(tid));
> +	}
>  #endif
>  	stat(s, CMPXCHG_DOUBLE_CPU_FAIL);
>  }
> -- 
> 2.43.0