perf sched: Make idle thread and comm/pid names more consistent

Peter noticed that we have 3 ways of referring to the idle thread:

 [idle]:0
 swapper:0
 swapper-0

Standardize on 'swapper:0'.
Reported-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-sched.c

@@ -1204,13 +1204,13 @@ static void output_lat_thread(struct work_atoms *work_list)
 	/*
 	 * Ignore idle threads:
 	 */
-	if (!work_list->thread->pid)
+	if (!strcmp(work_list->thread->comm, "swapper"))
 		return;
 
 	all_runtime += work_list->total_runtime;
 	all_count += work_list->nb_atoms;
 
-	ret = printf("  %s-%d ", work_list->thread->comm, work_list->thread->pid);
+	ret = printf("  %s:%d ", work_list->thread->comm, work_list->thread->pid);
 
 	for (i = 0; i < 24 - ret; i++)
 		printf(" ");

tools/perf/util/thread.c

@@ -85,7 +85,7 @@ register_idle_thread(struct rb_root *threads, struct thread **last_match)
 {
 	struct thread *thread = threads__findnew(0, threads, last_match);
 
-	if (!thread || thread__set_comm(thread, "[init]")) {
+	if (!thread || thread__set_comm(thread, "swapper")) {
 		fprintf(stderr, "problem inserting idle task.\n");
 		exit(-1);
 	}