linux-kernel - Re: [PATCH v6 7/7] tracing: Add a probe that attaches to trace events

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Date:   Thu, 19 Aug 2021 12:56:52 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Tzvetomir Stoyanov" <tz.stoyanov@...il.com>,
        Tom Zanussi <zanussi@...nel.org>,
        linux-trace-devel@...r.kernel.org
Subject: Re: [PATCH v6 7/7] tracing: Add a probe that attaches to trace
 events

On Wed, 18 Aug 2021 23:37:57 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:


> > Here, you don't check the event name collision. Since the kprobe event
> > supports multiprobe event, it checks the collision by itself.
> > See register_trace_kprobe().
> > BTW, I found another issue on the name collision. Let me fix it.
> 
> I'm thinking of adding this above before taking the event_mutex:
> 
> 	/* Check if the name already exists */
> 	if (find_event_probe(group, event))
> 		return -EEXIST;
> 
> Where I have:
> 
> static bool find_event_probe(const char *group, const char *event)
> {
> 	struct dyn_event *ev;
> 	struct trace_eprobe *ep;
> 
> 	for_each_dyn_event(ev) {
> 		if (ev->ops != &eprobe_dyn_event_ops)
> 			continue;
> 		
> 		ep = to_trace_eprobe(ev);
> 		if (strcmp(ep->tp.event->class.system, group) == 0 &&
> 		    strcmp(ep->tp.event->call.name, event) == 0)
> 			return true;
> 	}
> 	return false;
> }

Yeah, but I think this should be done with event_mutex, shouldn't it?

Thank you,


-- 
Masami Hiramatsu <mhiramat@...nel.org>