[PATCH 1/2] tracing: Return -ENOENT if there is no target synthetic event

[Masami Hiramatsu <mhiramat@xxxxxxxxxx>]

Return -ENOENT error if there is no target synthetic event.
This notices an operation failure to user as below;

  # echo 'wakeup_latency u64 lat; pid_t pid;' > synthetic_events
  # echo '!wakeup' >> synthetic_events
  sh: write error: No such file or directory

Fixes: 4b147936fa50 ('tracing: Add support for 'synthetic' events')
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace_events_hist.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index d239004aaf29..eb908ef2ecec 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1063,8 +1063,10 @@ static int create_synth_event(int argc, char **argv)
 		event = NULL;
 		ret = -EEXIST;
 		goto out;
-	} else if (delete_event)
+	} else if (delete_event) {
+		ret = -ENOENT;
 		goto out;
+	}
 
 	if (argc < 2) {
 		ret = -EINVAL;