tty: Fix hung task on pty hangup (fae76e9a) · Commits · 戴 / test

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 <sasha.levin@oracle.com> Reviewed-by:

Alan Cox <alan@linux.intel.com> Signed-off-by:

Peter Hurley <peter@hurleysoftware.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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);

Admin message