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Commit fae76e9a authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
Browse files

tty: Fix hung task on pty hangup 



When hanging up one end of a pty pair, there may be waiting
readers/writers on the other end which may not exit, preventing
tty_ldisc_lock_pair() 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 processing until after the ldisc hangup is complete.

Reported-by: default avatarSasha Levin <sasha.levin@oracle.com>
Reviewed-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e80a10ee

drivers/tty/tty_ldisc.c

+20 −2
Original line number Diff line number Diff line
@@ -325,6 +325,24 @@ static inline void __tty_ldisc_unlock(struct tty_struct *tty) 
	return ldsem_up_write(&tty->ldisc_sem);

}



static int __lockfunc

tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)

{

	int ret;



	ret = __tty_ldisc_lock(tty, timeout);

	if (!ret)

		return -EBUSY;

	set_bit(TTY_LDISC_HALTED, &tty->flags);

	return 0;

}



static void tty_ldisc_unlock(struct tty_struct *tty)

{

	clear_bit(TTY_LDISC_HALTED, &tty->flags);

	__tty_ldisc_unlock(tty);

}



static int __lockfunc

tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2,

			    unsigned long timeout)
@@ -682,7 +700,7 @@ void tty_ldisc_hangup(struct tty_struct *tty) 
	 *

	 * Avoid racing set_ldisc or tty_ldisc_release

	 */

	tty_ldisc_lock_pair(tty, tty->link);

	tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT);



	if (tty->ldisc) {
@@ -704,7 +722,7 @@ void tty_ldisc_hangup(struct tty_struct *tty) 
			WARN_ON(tty_ldisc_open(tty, tty->ldisc));

		}

	}

	tty_ldisc_enable_pair(tty, tty->link);

	tty_ldisc_unlock(tty);

	if (reset)

		tty_reset_termios(tty);