Merge the right tty-fixes branch

* branch 'tty-fixes'
  tty: use the new 'flush_delayed_work()' helper to do ldisc flush
  workqueue: add 'flush_delayed_work()' to run and wait for delayed work
  tty: Make flush_to_ldisc() locking more robust

kernel/workqueue.c

@@ -647,7 +647,7 @@ EXPORT_SYMBOL(schedule_delayed_work);
  */
 void flush_delayed_work(struct delayed_work *dwork)
 {
-	if (del_timer(&dwork->timer)) {
+	if (del_timer_sync(&dwork->timer)) {
 		struct cpu_workqueue_struct *cwq;
 		cwq = wq_per_cpu(keventd_wq, get_cpu());
 		__queue_work(cwq, &dwork->work);