perf top: Register idle thread

The perf top didn't add the idle/swapper thread to the machine's thread
list and its comm was displayed as ':0'.  Fix it.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1443577526-3240-3-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-top.c

@@ -964,6 +964,9 @@ static int __cmd_top(struct perf_top *top)
 	if (ret)
 		goto out_delete;
 
+	if (perf_session__register_idle_thread(top->session) == NULL)
+		goto out_delete;
+
 	machine__synthesize_threads(&top->session->machines.host, &opts->target,
 				    top->evlist->threads, false, opts->proc_map_timeout);
 

tools/perf/util/session.c

@@ -1311,7 +1311,7 @@ struct thread *perf_session__findnew(struct perf_session *session, pid_t pid)
 	return machine__findnew_thread(&session->machines.host, -1, pid);
 }
 
-static struct thread *perf_session__register_idle_thread(struct perf_session *session)
+struct thread *perf_session__register_idle_thread(struct perf_session *session)
 {
 	struct thread *thread;
 

tools/perf/util/session.h

@@ -89,6 +89,8 @@ struct machine *perf_session__findnew_machine(struct perf_session *session, pid_
 }
 
 struct thread *perf_session__findnew(struct perf_session *session, pid_t pid);
+struct thread *perf_session__register_idle_thread(struct perf_session *session);
+
 size_t perf_session__fprintf(struct perf_session *session, FILE *fp);
 
 size_t perf_session__fprintf_dsos(struct perf_session *session, FILE *fp);