---

yaml
---
r: 364253
b: refs/heads/master
c: 2276ad9
h: refs/heads/master
i:
  364251: e1a4697
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 168942c9fa01916173a7b72ac67e1d218d571013
+refs/heads/master: 2276ad9765b395577442d6ddf748f72c329234ae

trunk/drivers/tty/tty_ldisc.c

@@ -558,29 +558,29 @@ static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
  *	have been halted for this to guarantee it remains idle.
  *
  *	Caller must hold legacy and ->ldisc_mutex.
+ *
+ *	NB: tty_set_ldisc() is prevented from changing the ldisc concurrently
+ *	with this function by checking the TTY_HUPPING flag.
  */
 static bool tty_ldisc_hangup_wait_idle(struct tty_struct *tty)
 {
-	while (tty->ldisc) {	/* Not yet closed */
-		if (atomic_read(&tty->ldisc->users) != 1) {
-			char cur_n[TASK_COMM_LEN], tty_n[64];
-			long timeout = 3 * HZ;
-			tty_unlock(tty);
-
-			while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
-				timeout = MAX_SCHEDULE_TIMEOUT;
-				printk_ratelimited(KERN_WARNING
-					"%s: waiting (%s) for %s took too long, but we keep waiting...\n",
-					__func__, get_task_comm(cur_n, current),
-					tty_name(tty, tty_n));
-			}
-			/* must reacquire both locks and preserve lock order */
-			mutex_unlock(&tty->ldisc_mutex);
-			tty_lock(tty);
-			mutex_lock(&tty->ldisc_mutex);
-			continue;
+	char cur_n[TASK_COMM_LEN], tty_n[64];
+	long timeout = 3 * HZ;
+
+	if (tty->ldisc) {	/* Not yet closed */
+		tty_unlock(tty);
+
+		while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
+			timeout = MAX_SCHEDULE_TIMEOUT;
+			printk_ratelimited(KERN_WARNING
+				"%s: waiting (%s) for %s took too long, but we keep waiting...\n",
+				__func__, get_task_comm(cur_n, current),
+				tty_name(tty, tty_n));
 		}
-		break;
+		/* must reacquire both locks and preserve lock order */
+		mutex_unlock(&tty->ldisc_mutex);
+		tty_lock(tty);
+		mutex_lock(&tty->ldisc_mutex);
 	}
 	return !!tty->ldisc;
 }