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From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	"Tzvetomir Stoyanov" <tz.stoyanov@gmail.com>,
	Tom Zanussi <zanussi@kernel.org>,
	linux-trace-devel@vger.kernel.org
Subject: Re: [PATCH v6 7/7] tracing: Add a probe that attaches to trace events
Date: Thu, 19 Aug 2021 00:10:05 -0400	[thread overview]
Message-ID: <20210819001005.712e542a@oasis.local.home> (raw)
In-Reply-To: <20210819000342.615e68c7@oasis.local.home>

On Thu, 19 Aug 2021 00:03:42 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> Probably. I noticed that it was updated under the dyn_event_ops_mutex,
> and thought that was enough protection. But I now see the lockdep
> assert on the event_mutex in the other functions.

Anyway, here's the new version:

static bool find_event_probe(const char *group, const char *event)
{
	struct trace_eprobe *ep;
	struct dyn_event *ev;
	bool ret = false;

	/*
	 * Must grab the event_mutex to prevent the list from being modified
	 * by other probes. But the event_probe being only created via the
	 * dynamic_events file, is only added under the dyn_event_ops_mutex,
	 * which is currently held. There is no race between this check and
	 * adding the new probe.
	 */
	mutex_lock(&event_mutex);
	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) {
			ret = true;
			break;
		}
	}
	mutex_lock(&event_mutex);

	return ret;
}


-- Steve

  reply	other threads:[~2021-08-19  4:10 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-17  3:42 [PATCH v6 0/7] tracing: Creation of event probe Steven Rostedt
2021-08-17  3:42 ` [PATCH v6 1/7] tracing: Add DYNAMIC flag for dynamic events Steven Rostedt
2021-08-18  8:15   ` Masami Hiramatsu
2021-08-17  3:42 ` [PATCH v6 2/7] tracing: Have dynamic events have a ref counter Steven Rostedt
2021-08-18 16:14   ` Masami Hiramatsu
2021-08-17  3:42 ` [PATCH v6 3/7] tracing/probe: Have traceprobe_parse_probe_arg() take a const arg Steven Rostedt
2021-08-18 16:16   ` Masami Hiramatsu
2021-08-17  3:42 ` [PATCH v6 4/7] tracing/probes: Allow for dot delimiter as well as slash for system names Steven Rostedt
2021-08-18 10:57   ` Masami Hiramatsu
2021-08-17  3:43 ` [PATCH v6 5/7] tracing/probes: Use struct_size() instead of defining custom macros Steven Rostedt
2021-08-18 11:08   ` Masami Hiramatsu
2021-08-17  3:43 ` [PATCH v6 6/7] tracing/probe: Change traceprobe_set_print_fmt() to take a type Steven Rostedt
2021-08-18 16:19   ` Masami Hiramatsu
2021-08-17  3:43 ` [PATCH v6 7/7] tracing: Add a probe that attaches to trace events Steven Rostedt
2021-08-19  2:29   ` Masami Hiramatsu
2021-08-19  3:37     ` Steven Rostedt
2021-08-19  3:56       ` Masami Hiramatsu
2021-08-19  4:03         ` Steven Rostedt
2021-08-19  4:10           ` Steven Rostedt [this message]
2021-08-19  4:28           ` Masami Hiramatsu

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