From 36697529b5bbe36911e39a6309e7a7c9250d280a Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 15 Jun 2013 07:04:48 -0400 Subject: tty: Replace ldisc locking with ldisc_sem Line discipline locking was performed with a combination of a mutex, a status bit, a count, and a waitqueue -- basically, a rw semaphore. Replace the existing combination with an ld_semaphore. Fixes: 1) the 'reference acquire after ldisc locked' bug 2) the over-complicated halt mechanism 3) lock order wrt. tty_lock() 4) dropping locks while changing ldisc 5) previously unidentified deadlock while locking ldisc from both linked ttys concurrently 6) previously unidentified recursive deadlocks Adds much-needed lockdep diagnostics. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'drivers/tty/tty_io.c') diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index fa80af3656a3..0fa5db4c7a7a 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -1388,8 +1388,7 @@ static int tty_reopen(struct tty_struct *tty) struct tty_driver *driver = tty->driver; if (test_bit(TTY_CLOSING, &tty->flags) || - test_bit(TTY_HUPPING, &tty->flags) || - test_bit(TTY_LDISC_CHANGING, &tty->flags)) + test_bit(TTY_HUPPING, &tty->flags)) return -EIO; if (driver->type == TTY_DRIVER_TYPE_PTY && @@ -1405,7 +1404,7 @@ static int tty_reopen(struct tty_struct *tty) } tty->count++; - WARN_ON(!test_bit(TTY_LDISC, &tty->flags)); + WARN_ON(!tty->ldisc); return 0; } @@ -3017,7 +3016,7 @@ void initialize_tty_struct(struct tty_struct *tty, tty->pgrp = NULL; mutex_init(&tty->legacy_mutex); mutex_init(&tty->termios_mutex); - mutex_init(&tty->ldisc_mutex); + init_ldsem(&tty->ldisc_sem); init_waitqueue_head(&tty->write_wait); init_waitqueue_head(&tty->read_wait); INIT_WORK(&tty->hangup_work, do_tty_hangup); -- cgit v1.2.2