linux-kernel - Re: [PATCH] uprobe: Move arch_uprobe_optimize right after handlers execution

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Message-Id: <20251002082045.f9059a70eebea517e7cb67b8@kernel.org>
Date: Thu, 2 Oct 2025 08:20:45 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Andrii Nakryiko <andrii@...nel.org>, Linus Torvalds
 <torvalds@...ux-foundation.org>, bpf@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 x86@...nel.org, Song Liu <songliubraving@...com>, Yonghong Song
 <yhs@...com>, John Fastabend <john.fastabend@...il.com>, Hao Luo
 <haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Alan Maguire <alan.maguire@...cle.com>, David Laight
 <David.Laight@...LAB.COM>, Thomas Weißschuh
 <thomas@...ch.de>, Ingo Molnar <mingo@...nel.org>, Jann Horn
 <jannh@...gle.com>, Alejandro Colomar <alx@...nel.org>
Subject: Re: [PATCH] uprobe: Move arch_uprobe_optimize right after handlers
 execution

On Wed,  1 Oct 2025 15:24:49 +0200
Jiri Olsa <jolsa@...nel.org> wrote:

> It's less confusing to optimize uprobe right after handlers execution
> and before we do the check for changed ip register to avoid situations
> where changed ip register would skip uprobe optimization.
> 
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>

Looks good to me.

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


Thanks,

> ---
>  kernel/events/uprobes.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 5dcf927310fd..c14ec27b976d 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -2765,6 +2765,9 @@ static void handle_swbp(struct pt_regs *regs)
>  
>  	handler_chain(uprobe, regs);
>  
> +	/* Try to optimize after first hit. */
> +	arch_uprobe_optimize(&uprobe->arch, bp_vaddr);
> +
>  	/*
>  	 * If user decided to take execution elsewhere, it makes little sense
>  	 * to execute the original instruction, so let's skip it.
> @@ -2772,9 +2775,6 @@ static void handle_swbp(struct pt_regs *regs)
>  	if (instruction_pointer(regs) != bp_vaddr)
>  		goto out;
>  
> -	/* Try to optimize after first hit. */
> -	arch_uprobe_optimize(&uprobe->arch, bp_vaddr);
> -
>  	if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
>  		goto out;
>  
> -- 
> 2.51.0
> 


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