[PATCH 3/7] tracing: Add delete_synth_event()

[Tom Zanussi <zanussi@kernel.org>]

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 delete_synth_event().

Signed-off-by: Tom Zanussi <zanussi@kernel.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 cf982c7d6636..0c36a58cea43 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -358,6 +358,8 @@ extern struct trace_event_file *get_event_file_nolock(const char *instance,
 extern void put_event_file(struct trace_event_file *file);
 extern void put_event_file_nolock(struct trace_event_file *file);
 
+extern int delete_synth_event(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 f49d1a36d3ae..8c9894681100 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1335,29 +1335,54 @@ 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;
+}
+
+/**
+ * delete_synth_event - Delete a synthetic event
+ * @event_name: The name of the new sythetic event
+ *
+ * Delete a synthetic event that was created with create_synth_event().
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+int delete_synth_event(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(delete_synth_event);
+
 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 = delete_synth_event(name + 1);
 		return ret;
 	}
 
-- 
2.14.1