linux-kernel - [PATCH v3 03/12] tracing: Add synth_event

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Message-Id: <fb1828de7e276c5589071fe34f509a6cfba83cf7.1579904761.git.zanussi@kernel.org>
Date:   Fri, 24 Jan 2020 16:56:14 -0600
From:   Tom Zanussi <zanussi@...nel.org>
To:     rostedt@...dmis.org
Cc:     artem.bityutskiy@...ux.intel.com, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        ndesaulniers@...gle.com
Subject: [PATCH v3 03/12] tracing: Add synth_event_delete()

create_or_delete_synth_event() contains code to delete a synthetic
event, which would be useful on its own - specifically, it would be
useful to allow event-creating modules to call it separately.

Separate out the delete code from that function and create an exported
function named synth_event_delete().

Signed-off-by: Tom Zanussi <zanussi@...nel.org>
---
 include/linux/trace_events.h     |  2 ++
 kernel/trace/trace_events_hist.c | 57 +++++++++++++++++++++++++++++-----------
 2 files changed, 43 insertions(+), 16 deletions(-)

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 8d621a73c97e..25fe743bcbaf 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -354,6 +354,8 @@ extern struct trace_event_file *trace_get_event_file(const char *instance,
 						     const char *event);
 extern void trace_put_event_file(struct trace_event_file *file);
 
+extern int synth_event_delete(const char *name);
+
 /*
  * Event file flags:
  *  ENABLED	  - The event is enabled
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 117a1202a6b9..94ee1e576a1e 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1354,29 +1354,54 @@ static int __create_synth_event(int argc, const char *name, const char **argv)
 	goto out;
 }
 
+static int destroy_synth_event(struct synth_event *se)
+{
+	int ret;
+
+	if (se->ref)
+		ret = -EBUSY;
+	else {
+		ret = unregister_synth_event(se);
+		if (!ret) {
+			dyn_event_remove(&se->devent);
+			free_synth_event(se);
+		}
+	}
+
+	return ret;
+}
+
+/**
+ * synth_event_delete - Delete a synthetic event
+ * @event_name: The name of the new sythetic event
+ *
+ * Delete a synthetic event that was created with synth_event_create().
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+int synth_event_delete(const char *event_name)
+{
+	struct synth_event *se = NULL;
+	int ret = -ENOENT;
+
+	mutex_lock(&event_mutex);
+	se = find_synth_event(event_name);
+	if (se)
+		ret = destroy_synth_event(se);
+	mutex_unlock(&event_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(synth_event_delete);
+
 static int create_or_delete_synth_event(int argc, char **argv)
 {
 	const char *name = argv[0];
-	struct synth_event *event = NULL;
 	int ret;
 
 	/* trace_run_command() ensures argc != 0 */
 	if (name[0] == '!') {
-		mutex_lock(&event_mutex);
-		event = find_synth_event(name + 1);
-		if (event) {
-			if (event->ref)
-				ret = -EBUSY;
-			else {
-				ret = unregister_synth_event(event);
-				if (!ret) {
-					dyn_event_remove(&event->devent);
-					free_synth_event(event);
-				}
-			}
-		} else
-			ret = -ENOENT;
-		mutex_unlock(&event_mutex);
+		ret = synth_event_delete(name + 1);
 		return ret;
 	}
 
-- 
2.14.1