perf tools: Notify user when unrecognized event is specified

Previously no indication was given about what went wrong.
Signed-off-by: Marti Raudsepp <marti@juffo.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <03ec9ee96f17cef05424.1256603584@localhost>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/util/parse-events.c

@@ -678,6 +678,8 @@ parse_event_symbols(const char **str, struct perf_event_attr *attr)
 	if (ret != EVT_FAILED)
 		goto modifier;
 
+	fprintf(stderr, "invalid or unsupported event: '%s'\n", *str);
+	fprintf(stderr, "Run 'perf list' for a list of valid events\n");
 	return EVT_FAILED;
 
 modifier: