From fae76e9adfa450f4c2dd5773265eb3c811a9c484 Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Wed, 5 Nov 2014 12:13:07 -0500 Subject: [PATCH] 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: Sasha Levin Reviewed-by: Alan Cox Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_ldisc.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index 5bdc241628ac..1dbe27824220 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -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);