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

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Message-Id: <20241210110428.aa5446ca9b2153c21f8fcdf9@kernel.org>
Date: Tue, 10 Dec 2024 11:04:28 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Peter Zijlstra <peterz@...radead.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, 9 Dec 2024 12:04:11 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> 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 ?

Good catch! It has not been updated for static_call_text_reserved().
We need static_call_lock() here too.

Thanks!

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