perf: Don't print traces when debugging ordering

Errors due to ordering bugs are easily lost in the middle
of traces.

When we are in this mode, don't print the traces so that
we don't miss the debugging messages.
But display a comforting message if we didn't encounter any
ordering problem.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>

tools/perf/builtin-trace.c

@@ -13,6 +13,7 @@ static char const		*script_name;
 static char const		*generate_script_lang;
 static bool			debug_ordering;
 static u64			last_timestamp;
+static u64			nr_unordered;
 
 static int default_start_script(const char *script __unused,
 				int argc __unused,
@@ -96,8 +97,10 @@ static int process_sample_event(event_t *event, struct perf_session *session)
 				pr_err("Samples misordered, previous: %llu "
 					"this: %llu\n", last_timestamp,
 					data.time);
+				nr_unordered++;
 			}
 			last_timestamp = data.time;
+			return 0;
 		}
 		/*
 		 * FIXME: better resolve from pid from the struct trace_entry
@@ -132,9 +135,16 @@ static void sig_handler(int sig __unused)
 
 static int __cmd_trace(struct perf_session *session)
 {
+	int ret;
+
 	signal(SIGINT, sig_handler);
 
-	return perf_session__process_events(session, &event_ops);
+	ret = perf_session__process_events(session, &event_ops);
+
+	if (debug_ordering)
+		pr_err("Misordered timestamps: %llu\n", nr_unordered);
+
+	return ret;
 }
 
 struct script_spec {