Merge tag 'tty-4.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial updates from Greg KH:
 "Here is the big serial/tty driver update for 4.5-rc1.

  Lots of driver updates and some tty core changes.  All of these have
  been in linux-next and the details are in the shortlog"

* tag 'tty-4.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (127 commits)
  drivers/tty/serial: delete unused MODULE_DEVICE_TABLE from atmel_serial.c
  serial: sh-sci: Remove cpufreq notifier to fix crash/deadlock
  serial: 8250: of: Fix the driver and actually compile the 8250_of
  tty: amba-pl011: use iotype instead of access_32b to track 32-bit I/O
  tty: amba-pl011: fix earlycon register offsets
  serial: sh-sci: Drop the sci_fck clock fallback
  sh: sh7734: Correct SCIF type for BRG
  sh: Remove sci_ick clock alias
  sh: Rename sci_ick and sci_fck clock to fck
  serial: sh-sci: Add support for optional BRG on (H)SCIF
  serial: sh-sci: Add support for optional external (H)SCK input
  serial: sh-sci: Prepare for multiple sampling clock sources
  serial: sh-sci: Correct SCIF type on R-Car for BRG
  serial: sh-sci: Correct SCIF type on RZ/A1H
  serial: sh-sci: Replace struct sci_port_info by type/regtype encoding
  serial: sh-sci: Add BRG register definitions
  serial: sh-sci: Take into account sampling rate for max baud rate
  serial: sh-sci: Merge sci_scbrr_calc() and sci_baud_calc_hscif()
  serial: sh-sci: Avoid calculating the receive margin for HSCIF
  serial: sh-sci: Improve bit rate error calculation for HSCIF
  ...

1 files changed, 21 insertions, 30 deletions

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 629e3c865072..a054d03c22e7 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -185,7 +185,7 @@ static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc)
  *
  *	Complement of tty_ldisc_get().
  */
-static inline void tty_ldisc_put(struct tty_ldisc *ld)
+static void tty_ldisc_put(struct tty_ldisc *ld)
 {
 	if (WARN_ON_ONCE(!ld))
 		return;
@@ -417,6 +417,10 @@ EXPORT_SYMBOL_GPL(tty_ldisc_flush);
  *	they are not on hot paths so a little discipline won't do
  *	any harm.
  *
+ *	The line discipline-related tty_struct fields are reset to
+ *	prevent the ldisc driver from re-using stale information for
+ *	the new ldisc instance.
+ *
  *	Locking: takes termios_rwsem
  */
 
@@ -425,6 +429,9 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
 	down_write(&tty->termios_rwsem);
 	tty->termios.c_line = num;
 	up_write(&tty->termios_rwsem);
+
+	tty->disc_data = NULL;
+	tty->receive_room = 0;
 }
 
 /**
@@ -529,34 +536,21 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 
 	tty_lock(tty);
 	retval = tty_ldisc_lock(tty, 5 * HZ);
-	if (retval) {
-		tty_ldisc_put(new_ldisc);
-		tty_unlock(tty);
-		return retval;
-	}
+	if (retval)
+		goto err;
 
-	/*
-	 *	Check the no-op case
-	 */
+	/* Check the no-op case */
+	if (tty->ldisc->ops->num == ldisc)
+		goto out;
 
-	if (tty->ldisc->ops->num == ldisc) {
-		tty_ldisc_unlock(tty);
-		tty_ldisc_put(new_ldisc);
-		tty_unlock(tty);
-		return 0;
+	if (test_bit(TTY_HUPPED, &tty->flags)) {
+		/* We were raced by hangup */
+		retval = -EIO;
+		goto out;
 	}
 
 	old_ldisc = tty->ldisc;
 
-	if (test_bit(TTY_HUPPED, &tty->flags)) {
-		/* We were raced by the hangup method. It will have stomped
-		   the ldisc data and closed the ldisc down */
-		tty_ldisc_unlock(tty);
-		tty_ldisc_put(new_ldisc);
-		tty_unlock(tty);
-		return -EIO;
-	}
-
 	/* Shutdown the old discipline. */
 	tty_ldisc_close(tty, old_ldisc);
 
@@ -582,18 +576,15 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 	   the old ldisc (if it was restored as part of error cleanup
 	   above). In either case, releasing a single reference from
 	   the old ldisc is correct. */
-
-	tty_ldisc_put(old_ldisc);
-
-	/*
-	 *	Allow ldisc referencing to occur again
-	 */
+	new_ldisc = old_ldisc;
+out:
 	tty_ldisc_unlock(tty);
 
 	/* Restart the work queue in case no characters kick it off. Safe if
 	   already running */
 	tty_buffer_restart_work(tty->port);
-
+err:
+	tty_ldisc_put(new_ldisc);	/* drop the extra reference */
 	tty_unlock(tty);
 	return retval;
 }