linux-kernel - Re: [PATCH] tracing/eprobe: Iterate trace

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Message-Id: <20230811105102.f7c1a2d08700df1c226f096f@kernel.org>
Date:   Fri, 11 Aug 2023 10:51:02 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Masami Hiramatsu (Google) <mhiramat@...nel.org>
Cc:     Chuang Wang <nashuiliang@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@...il.com>,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing/eprobe: Iterate trace_eprobe directly

On Thu, 10 Aug 2023 19:32:04 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:

> On Thu, 10 Aug 2023 16:25:23 +0800
> Chuang Wang <nashuiliang@...il.com> wrote:
> 
> > Refer to the description in [1], we can skip "container_of()" following
> > "list_for_each_entry()" by using "list_for_each_entry()" with
> > "struct trace_eprobe" and "tp.list".
> > 
> > [1] https://lore.kernel.org/all/CAHk-=wjakjw6-rDzDDBsuMoDCqd+9ogifR_EE1F0K-jYek1CdA@mail.gmail.com/
> > 
> 
> Good point. BTW, it is better to have 'for_each_eprobe(ep)' if it repeats 3 times.

Wait, it is for each trace_eprobe on the trace_probe.

#define for_each_trace_eprobe_on_trace_probe(ep, _tp)
	list_for_each_entry(ep, trace_probe_probe_list(_tp), tp.list)

Thank you,

> 
> 
> > Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events")
> 
> This is not a bug, so no need Fixes tag.
> 
> Thank you,
> 
> > Signed-off-by: Chuang Wang <nashuiliang@...il.com>
> > ---
> >  kernel/trace/trace_eprobe.c | 13 +++++--------
> >  1 file changed, 5 insertions(+), 8 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
> > index a0a704ba27db..d68d660dff7c 100644
> > --- a/kernel/trace/trace_eprobe.c
> > +++ b/kernel/trace/trace_eprobe.c
> > @@ -640,7 +640,7 @@ static int disable_eprobe(struct trace_eprobe *ep,
> >  static int enable_trace_eprobe(struct trace_event_call *call,
> >  			       struct trace_event_file *file)
> >  {
> > -	struct trace_probe *pos, *tp;
> > +	struct trace_probe *tp;
> >  	struct trace_eprobe *ep;
> >  	bool enabled;
> >  	int ret = 0;
> > @@ -662,8 +662,7 @@ static int enable_trace_eprobe(struct trace_event_call *call,
> >  	if (enabled)
> >  		return 0;
> >  
> > -	list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
> > -		ep = container_of(pos, struct trace_eprobe, tp);
> > +	list_for_each_entry(ep, trace_probe_probe_list(tp), tp.list) {
> >  		ret = enable_eprobe(ep, file);
> >  		if (ret)
> >  			break;
> > @@ -680,8 +679,7 @@ static int enable_trace_eprobe(struct trace_event_call *call,
> >  			 */
> >  			WARN_ON_ONCE(ret != -ENOMEM);
> >  
> > -			list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
> > -				ep = container_of(pos, struct trace_eprobe, tp);
> > +			list_for_each_entry(ep, trace_probe_probe_list(tp), tp.list) {
> >  				disable_eprobe(ep, file->tr);
> >  				if (!--cnt)
> >  					break;
> > @@ -699,7 +697,7 @@ static int enable_trace_eprobe(struct trace_event_call *call,
> >  static int disable_trace_eprobe(struct trace_event_call *call,
> >  				struct trace_event_file *file)
> >  {
> > -	struct trace_probe *pos, *tp;
> > +	struct trace_probe *tp;
> >  	struct trace_eprobe *ep;
> >  
> >  	tp = trace_probe_primary_from_call(call);
> > @@ -716,8 +714,7 @@ static int disable_trace_eprobe(struct trace_event_call *call,
> >  		trace_probe_clear_flag(tp, TP_FLAG_PROFILE);
> >  
> >  	if (!trace_probe_is_enabled(tp)) {
> > -		list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
> > -			ep = container_of(pos, struct trace_eprobe, tp);
> > +		list_for_each_entry(ep, trace_probe_probe_list(tp), tp.list) {
> >  			disable_eprobe(ep, file->tr);
> >  		}
> >  	}
> > -- 
> > 2.39.2
> > 
> 
> 
> -- 
> Masami Hiramatsu (Google) <mhiramat@...nel.org>


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