From 276a661a4d75258b3aa28701b0748f99b773563b Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Wed, 5 Nov 2014 12:13:08 -0500 Subject: [PATCH] tty: Fix timeout on pty set ldisc When changing the ldisc on one end of a pty pair, there may be waiting readers/writers on the other end which may not exit from the ldisc i/o loop, preventing tty_ldisc_lock_pair_timeout() from acquiring the other side's ldisc lock. Only acquire this side's ldisc lock; although this will no longer prevent the other side from writing new input, that input will not be processed until after the ldisc change completes. This has no effect on normal ttys; new input from the driver was never disabled. Remove tty_ldisc_enable_pair(). Reviewed-by: Alan Cox Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_ldisc.c | 21 ++++----------------- 1 file changed, 4 insertions(+), 17 deletions(-) diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index 1dbe27824220..6368dd95e137 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -393,16 +393,6 @@ static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty, __tty_ldisc_unlock(tty2); } -static void __lockfunc tty_ldisc_enable_pair(struct tty_struct *tty, - struct tty_struct *tty2) -{ - clear_bit(TTY_LDISC_HALTED, &tty->flags); - if (tty2) - clear_bit(TTY_LDISC_HALTED, &tty2->flags); - - tty_ldisc_unlock_pair(tty, tty2); -} - /** * tty_ldisc_flush - flush line discipline queue * @tty: tty @@ -535,14 +525,13 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) { int retval; struct tty_ldisc *old_ldisc, *new_ldisc; - struct tty_struct *o_tty = tty->link; new_ldisc = tty_ldisc_get(tty, ldisc); if (IS_ERR(new_ldisc)) return PTR_ERR(new_ldisc); tty_lock(tty); - retval = tty_ldisc_lock_pair_timeout(tty, o_tty, 5 * HZ); + retval = tty_ldisc_lock(tty, 5 * HZ); if (retval) { tty_ldisc_put(new_ldisc); tty_unlock(tty); @@ -554,7 +543,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) */ if (tty->ldisc->ops->num == ldisc) { - tty_ldisc_enable_pair(tty, o_tty); + tty_ldisc_unlock(tty); tty_ldisc_put(new_ldisc); tty_unlock(tty); return 0; @@ -565,7 +554,7 @@ int tty_set_ldisc(struct tty_struct *tty, int 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_enable_pair(tty, o_tty); + tty_ldisc_unlock(tty); tty_ldisc_put(new_ldisc); tty_unlock(tty); return -EIO; @@ -599,13 +588,11 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc) /* * Allow ldisc referencing to occur again */ - tty_ldisc_enable_pair(tty, o_tty); + tty_ldisc_unlock(tty); /* Restart the work queue in case no characters kick it off. Safe if already running */ schedule_work(&tty->port->buf.work); - if (o_tty) - schedule_work(&o_tty->port->buf.work); tty_unlock(tty); return retval; -- 2.20.1