tty: Convert termios_mutex to termios_rwsem

termios is commonly accessed unsafely (especially by N_TTY)
because the existing mutex forces exclusive access.
Convert existing usage.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/irda/irtty-sir.c

@@ -123,14 +123,14 @@ static int irtty_change_speed(struct sir_dev *dev, unsigned speed)
 
 	tty = priv->tty;
 
-	mutex_lock(&tty->termios_mutex);
+	down_write(&tty->termios_rwsem);
 	old_termios = tty->termios;
 	cflag = tty->termios.c_cflag;
 	tty_encode_baud_rate(tty, speed, speed);
 	if (tty->ops->set_termios)
 		tty->ops->set_termios(tty, &old_termios);
 	priv->io.speed = speed;
-	mutex_unlock(&tty->termios_mutex);
+	up_write(&tty->termios_rwsem);
 
 	return 0;
 }
@@ -280,7 +280,7 @@ static inline void irtty_stop_receiver(struct tty_struct *tty, int stop)
 	struct ktermios old_termios;
 	int cflag;
 
-	mutex_lock(&tty->termios_mutex);
+	down_write(&tty->termios_rwsem);
 	old_termios = tty->termios;
 	cflag = tty->termios.c_cflag;
 
@@ -292,7 +292,7 @@ static inline void irtty_stop_receiver(struct tty_struct *tty, int stop)
 	tty->termios.c_cflag = cflag;
 	if (tty->ops->set_termios)
 		tty->ops->set_termios(tty, &old_termios);
-	mutex_unlock(&tty->termios_mutex);
+	up_write(&tty->termios_rwsem);
 }
 
 /*****************************************************************/

drivers/tty/n_tty.c

@@ -1539,7 +1539,7 @@ int is_ignored(int sig)
  *	guaranteed that this function will not be re-entered or in progress
  *	when the ldisc is closed.
  *
- *	Locking: Caller holds tty->termios_mutex
+ *	Locking: Caller holds tty->termios_rwsem
  */
 
 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)

drivers/tty/pty.c

@@ -287,7 +287,7 @@ static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 	struct tty_struct *pty = tty->link;
 
 	/* For a PTY we need to lock the tty side */
-	mutex_lock(&tty->termios_mutex);
+	down_write(&tty->termios_rwsem);
 	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 		goto done;
 
@@ -314,7 +314,7 @@ static int pty_resize(struct tty_struct *tty,  struct winsize *ws)
 	tty->winsize = *ws;
 	pty->winsize = *ws;	/* Never used so will go away soon */
 done:
-	mutex_unlock(&tty->termios_mutex);
+	up_write(&tty->termios_rwsem);
 	return 0;
 }
 

drivers/tty/tty_io.c

@@ -604,7 +604,7 @@ static int tty_signal_session_leader(struct tty_struct *tty, int exit_session)
  *		  redirect lock for undoing redirection
  *		  file list lock for manipulating list of ttys
  *		  tty_ldiscs_lock from called functions
- *		  termios_mutex resetting termios data
+ *		  termios_rwsem resetting termios data
  *		  tasklist_lock to walk task list for hangup event
  *		    ->siglock to protect ->signal/->sighand
  */
@@ -2230,17 +2230,17 @@ static int tiocsti(struct tty_struct *tty, char __user *p)
  *
  *	Copies the kernel idea of the window size into the user buffer.
  *
- *	Locking: tty->termios_mutex is taken to ensure the winsize data
+ *	Locking: tty->termios_rwsem is taken to ensure the winsize data
  *		is consistent.
  */
 
 static int tiocgwinsz(struct tty_struct *tty, struct winsize __user *arg)
 {
 	int err;
 
-	mutex_lock(&tty->termios_mutex);
+	down_read(&tty->termios_rwsem);
 	err = copy_to_user(arg, &tty->winsize, sizeof(*arg));
-	mutex_unlock(&tty->termios_mutex);
+	up_read(&tty->termios_rwsem);
 
 	return err ? -EFAULT: 0;
 }
@@ -2261,7 +2261,7 @@ int tty_do_resize(struct tty_struct *tty, struct winsize *ws)
 	unsigned long flags;
 
 	/* Lock the tty */
-	mutex_lock(&tty->termios_mutex);
+	down_write(&tty->termios_rwsem);
 	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
 		goto done;
 	/* Get the PID values and reference them so we can
@@ -2276,7 +2276,7 @@ int tty_do_resize(struct tty_struct *tty, struct winsize *ws)
 
 	tty->winsize = *ws;
 done:
-	mutex_unlock(&tty->termios_mutex);
+	up_write(&tty->termios_rwsem);
 	return 0;
 }
 EXPORT_SYMBOL(tty_do_resize);
@@ -3015,7 +3015,7 @@ void initialize_tty_struct(struct tty_struct *tty,
 	tty->session = NULL;
 	tty->pgrp = NULL;
 	mutex_init(&tty->legacy_mutex);
-	mutex_init(&tty->termios_mutex);
+	init_rwsem(&tty->termios_rwsem);
 	init_ldsem(&tty->ldisc_sem);
 	init_waitqueue_head(&tty->write_wait);
 	init_waitqueue_head(&tty->read_wait);