[PATCH -next v2 01/26] tty: Don't hold tty_lock for ldisc release

Peter Hurley
2014-11-05T17:13:35Z

The tty->ldisc_sem write lock is sufficient for serializing changes
to tty->ldisc; holding the tty lock is not required.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/tty_ldisc.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
index 2d822aa..332a622 100644
--- a/drivers/tty/tty_ldisc.c
+++ b/drivers/tty/tty_ldisc.c
@@ -764,6 +764,8 @@ static void tty_ldisc_kill(struct tty_struct *tty)
* Called during the final close of a tty/pty pair in order to shut down
* the line discpline layer. On exit the ldisc assigned is N_TTY and the
* ldisc has not been opened.
+ *
+ * Holding ldisc_sem write lock serializes tty->ldisc changes.
*/

void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
@@ -776,13 +778,9 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc);

tty_ldisc_lock_pair(tty, o_tty);
- tty_lock_pair(tty, o_tty);
-
tty_ldisc_kill(tty);
if (o_tty)
tty_ldisc_kill(o_tty);
-
- tty_unlock_pair(tty, o_tty);
tty_ldisc_unlock_pair(tty, o_tty);

/* And the memory resources remaining (buffers, termios) will be
--
2.1.3