kthread_bind: use wait_task_inactive(TASK_UNINTERRUPTIBLE)

Now that wait_task_inactive(task, state) checks task->state == state,
we can simplify the code and make this debugging check more robust.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kthread.c

@@ -171,12 +171,11 @@ EXPORT_SYMBOL(kthread_create);
  */
 void kthread_bind(struct task_struct *k, unsigned int cpu)
 {
-	if (k->state != TASK_UNINTERRUPTIBLE) {
+	/* Must have done schedule() in kthread() before we set_task_cpu */
+	if (!wait_task_inactive(k, TASK_UNINTERRUPTIBLE)) {
 		WARN_ON(1);
 		return;
 	}
-	/* Must have done schedule() in kthread() before we set_task_cpu */
-	wait_task_inactive(k, 0);
 	set_task_cpu(k, cpu);
 	k->cpus_allowed = cpumask_of_cpu(cpu);
 	k->rt.nr_cpus_allowed = 1;