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 <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-top.c

···
 	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

···
 	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

···
 }
 
 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);