linux-kernel - Re: [PATCH] kprobes: drop the unnecessary unlikely()

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Date:   Wed, 15 Jun 2022 09:15:01 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     l3b2w1@...il.com
Cc:     naveen.n.rao@...ux.ibm.com, anil.s.keshavamurthy@...el.com,
        davem@...emloft.net, linux-kernel@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] kprobes: drop the unnecessary unlikely()

On Mon, 13 Jun 2022 12:25:36 +0800
l3b2w1@...il.com wrote:

> From: "binglei.wang" <l3b2w1@...il.com>
> 
> !ap is likely when checking re-registering existing kprobe.
> 	register_kprobe -> warn_kprobe_rereg -> __get_valid_kprobe
> 
> !ap is unlikely when checking whether the kprobe is valid
> on enable/disable ocassion.
> 	__disable_kprobe/enable_kprobe -> __get_valid_kprobe
> 
> Considering these two cases, choose to drop the unlikely() here.
> 
> Signed-off-by: binglei.wang <l3b2w1@...il.com>

This looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thank you!

> ---
>  kernel/kprobes.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index f214f8c08..f4a829d98 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1504,7 +1504,7 @@ static struct kprobe *__get_valid_kprobe(struct kprobe *p)
>  	lockdep_assert_held(&kprobe_mutex);
>  
>  	ap = get_kprobe(p->addr);
> -	if (unlikely(!ap))
> +	if (!ap)
>  		return NULL;
>  
>  	if (p != ap) {
> -- 
> 2.27.0
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>