linux-kernel - Re: [PATCH v3 3/5] tracing: Use __free() for kprobe events to cleanup

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Message-Id: <20250108094051.f6b72d853fd9a67638ec5bc6@kernel.org>
Date: Wed, 8 Jan 2025 09:40:51 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Peter Zijlstra <peterz@...radead.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 v3 3/5] tracing: Use __free() for kprobe events to
 cleanup

On Tue, 7 Jan 2025 10:42:31 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue,  7 Jan 2025 20:50:35 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
> 
> > @@ -1898,7 +1899,8 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
> >  			  bool is_return)
> >  {
> >  	enum probe_print_type ptype;
> > -	struct trace_kprobe *tk;
> > +	struct trace_kprobe *tk __free(free_trace_kprobe) = NULL;
> > +	struct trace_probe *tp;
> >  	int ret;
> >  	char *event;
> >  
> > @@ -1929,19 +1931,16 @@ create_local_trace_kprobe(char *func, void *addr, unsigned long offs,
> >  
> >  	ptype = trace_kprobe_is_return(tk) ?
> >  		PROBE_PRINT_RETURN : PROBE_PRINT_NORMAL;
> > -	if (traceprobe_set_print_fmt(&tk->tp, ptype) < 0) {
> > -		ret = -ENOMEM;
> > -		goto error;
> > -	}
> > +	if (traceprobe_set_print_fmt(&tk->tp, ptype) < 0)
> > +		return ERR_PTR(-ENOMEM);
> >  
> >  	ret = __register_trace_kprobe(tk);
> >  	if (ret < 0)
> > -		goto error;
> > +		return ERR_PTR(ret);
> >  
> > -	return trace_probe_event_call(&tk->tp);
> > -error:
> > -	free_trace_kprobe(tk);
> > -	return ERR_PTR(ret);
> 
> 
> > +	tp = &tk->tp;
> > +	tk = NULL;	/* 'tk' is registered successfully, so do not free. */
> 
> I wonder if we could change the above to just:
> 
> 	tp = &(no_free_ptr(tk)->tp);

Ah, that's nice idea. Then I can remove 'tp' as;

	return trace_probe_event_call(&(no_free_ptr(tk)->tp));

Thanks!

> 
> ?
> 
> -- Steve
> 
> > +	return trace_probe_event_call(tp);
> >  }
> >  
> >  void destroy_local_trace_kprobe(struct trace_event_call *event_call)
> 

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