trace: print a warning if user tries to enable an unknown trace event

There was no warning if a bad trace event name was given to
'trace-event' command, thus the user could think that the command
was successful even if this was not the case.

Print a warning if the user tries to enable a trace event which is not
known.

Acked-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/monitor.c b/monitor.c
index fbb678d789..260cc02963 100644
--- a/monitor.c
+++ b/monitor.c
@@ -549,7 +549,11 @@ static void do_change_trace_event_state(Monitor *mon, const QDict *qdict)
 {
     const char *tp_name = qdict_get_str(qdict, "name");
     bool new_state = qdict_get_bool(qdict, "option");
-    st_change_trace_event_state(tp_name, new_state);
+    int ret = st_change_trace_event_state(tp_name, new_state);
+
+    if (!ret) {
+        monitor_printf(mon, "unknown event name \"%s\"\n", tp_name);
+    }
 }
 
 static void do_trace_file(Monitor *mon, const QDict *qdict)