linux-kernel - Re: [PATCH 2/5] kprobes: Use guard() for external locks

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Message-ID: <20241209110411.GL21636@noisy.programming.kicks-ass.net>
Date: Mon, 9 Dec 2024 12:04:11 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S . Miller" <davem@...emloft.net>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
	Naveen N Rao <naveen@...nel.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Jason Baron <jbaron@...mai.com>, Ard Biesheuvel <ardb@...nel.org>,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] kprobes: Use guard() for external locks

On Mon, Dec 09, 2024 at 11:41:26AM +0900, Masami Hiramatsu (Google) wrote:
> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Use guard() for text_mutex, cpu_read_lock, and jump_label_lock in
> the kprobes.

> @@ -853,29 +850,24 @@ static void try_to_optimize_kprobe(struct kprobe *p)
>  		return;
>  
>  	/* For preparing optimization, jump_label_text_reserved() is called. */
> -	cpus_read_lock();
> -	jump_label_lock();
> -	mutex_lock(&text_mutex);
> +	guard(cpus_read_lock)();
> +	guard(jump_label_lock)();
> +	guard(mutex)(&text_mutex);
>  

> @@ -1294,62 +1280,55 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
>  	int ret = 0;
>  	struct kprobe *ap = orig_p;
>  
> -	cpus_read_lock();
> -
> -	/* For preparing optimization, jump_label_text_reserved() is called */
> -	jump_label_lock();
> -	mutex_lock(&text_mutex);

Why does kprobe need jump_label_lock and how does it then not also need
static_call_lock ?