[PATCH -next 10/27] tty: Don't take tty_mutex for tty count changes

Peter Hurley
2014-10-16T21:01:39Z

Holding tty_mutex is no longer required to serialize changes to
the tty_count or to prevent concurrent opens of closing ttys;
tty_lock() is sufficient.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/tty_io.c | 6 ------
1 file changed, 6 deletions(-)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 55f9931..7b40247 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1805,10 +1805,6 @@ int tty_release(struct inode *inode, struct file *filp)
* each iteration we avoid any problems.
*/
while (1) {
- /* Guard against races with tty->count changes elsewhere and
- opens on /dev/tty */
-
- mutex_lock(&tty_mutex);
tty_lock_pair(tty, o_tty);
tty_closing = tty->count <= 1;
o_tty_closing = o_tty &&
@@ -1844,7 +1840,6 @@ int tty_release(struct inode *inode, struct file *filp)
__func__, tty_name(tty, buf));
}
tty_unlock_pair(tty, o_tty);
- mutex_unlock(&tty_mutex);
schedule_timeout_killable(timeout);
if (timeout < 120 * HZ)
timeout = 2 * timeout + 1;
@@ -1899,7 +1894,6 @@ int tty_release(struct inode *inode, struct file *filp)
read_unlock(&tasklist_lock);
}

- mutex_unlock(&tty_mutex);
tty_unlock_pair(tty, o_tty);
/* At this point, the tty->count == 0 should ensure a dead tty
cannot be re-opened by a racing opener */
--
2.1.1