--- zzzz-none-000/linux-3.10.107/drivers/tty/tty_mutex.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/drivers/tty/tty_mutex.c	2021-02-04 17:41:59.000000000 +0000
@@ -6,17 +6,11 @@
 
 /* Legacy tty mutex glue */
 
-enum {
-	TTY_MUTEX_NORMAL,
-	TTY_MUTEX_NESTED,
-};
-
 /*
  * Getting the big tty mutex.
  */
 
-static void __lockfunc tty_lock_nested(struct tty_struct *tty,
-				       unsigned int subclass)
+void __lockfunc tty_lock(struct tty_struct *tty)
 {
 	if (tty->magic != TTY_MAGIC) {
 		pr_err("L Bad %p\n", tty);
@@ -24,14 +18,17 @@
 		return;
 	}
 	tty_kref_get(tty);
-	mutex_lock_nested(&tty->legacy_mutex, subclass);
+	mutex_lock(&tty->legacy_mutex);
 }
+EXPORT_SYMBOL(tty_lock);
 
-void __lockfunc tty_lock(struct tty_struct *tty)
+int tty_lock_interruptible(struct tty_struct *tty)
 {
-	return tty_lock_nested(tty, TTY_MUTEX_NORMAL);
+	if (WARN(tty->magic != TTY_MAGIC, "L Bad %p\n", tty))
+		return -EIO;
+	tty_kref_get(tty);
+	return mutex_lock_interruptible(&tty->legacy_mutex);
 }
-EXPORT_SYMBOL(tty_lock);
 
 void __lockfunc tty_unlock(struct tty_struct *tty)
 {
@@ -45,29 +42,19 @@
 }
 EXPORT_SYMBOL(tty_unlock);
 
-/*
- * Getting the big tty mutex for a pair of ttys with lock ordering
- * On a non pty/tty pair tty2 can be NULL which is just fine.
- */
-void __lockfunc tty_lock_pair(struct tty_struct *tty,
-					struct tty_struct *tty2)
+void __lockfunc tty_lock_slave(struct tty_struct *tty)
 {
-	if (tty < tty2) {
+	if (tty && tty != tty->link)
 		tty_lock(tty);
-		tty_lock_nested(tty2, TTY_MUTEX_NESTED);
-	} else {
-		if (tty2 && tty2 != tty)
-			tty_lock(tty2);
-		tty_lock_nested(tty, TTY_MUTEX_NESTED);
-	}
 }
-EXPORT_SYMBOL(tty_lock_pair);
 
-void __lockfunc tty_unlock_pair(struct tty_struct *tty,
-						struct tty_struct *tty2)
+void __lockfunc tty_unlock_slave(struct tty_struct *tty)
+{
+	if (tty && tty != tty->link)
+		tty_unlock(tty);
+}
+
+void tty_set_lock_subclass(struct tty_struct *tty)
 {
-	tty_unlock(tty);
-	if (tty2 && tty2 != tty)
-		tty_unlock(tty2);
+	lockdep_set_subclass(&tty->legacy_mutex, TTY_LOCK_SLAVE);
 }
-EXPORT_SYMBOL(tty_unlock_pair);