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

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Message-Id: <20230810193204.cae5808af79bbcc80b88ff77@kernel.org>
Date:   Thu, 10 Aug 2023 19:32:04 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Chuang Wang <nashuiliang@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.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 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.


> 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>