diff options
| author |   Peter Hurley <peter@hurleysoftware.com> | 2013-06-15 07:04:48 -0400 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-07-23 16:38:34 -0700 |
| commit | 36697529b5bbe36911e39a6309e7a7c9250d280a (patch) | |
| tree | 5cbffa976994cb798e00d60eccb46c6cafc369a1 /drivers/tty/tty_io.c | |
| parent | tty: Add lock/unlock ldisc pair functions (diff) | |
| download | linux-dev-36697529b5bbe36911e39a6309e7a7c9250d280a.tar.xz linux-dev-36697529b5bbe36911e39a6309e7a7c9250d280a.zip | |
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 <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/tty_io.c')
| -rw-r--r-- | drivers/tty/tty_io.c | 7 |
1 files changed, 3 insertions, 4 deletions
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); |