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Commit 52bce7f8 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
Browse files

pty, n_tty: Simplify input processing on final close 



When releasing one end of a pty pair, that end may just have written
to the other, which the input processing worker, flush_to_ldisc(), is
still working on but has not completed the copy to the other end's
read buffer. So input may not appear to be available to a waiting
reader but yet TTY_OTHER_CLOSED is now observed. The n_tty line
discipline has worked around this by waiting for input processing
to complete and then re-checking if input is available before
exiting with -EIO.

Since the tty/ldisc lock reordering, the wait for input processing
to complete can now occur during final close before setting
TTY_OTHER_CLOSED. In this way, a waiting reader is guaranteed to
see input available (if any) before observing TTY_OTHER_CLOSED.

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 1bb95415

drivers/tty/n_tty.c

+20 −26
Original line number Diff line number Diff line
@@ -2197,14 +2197,9 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, 


		if (!input_available_p(tty, 0)) {

			if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {

				up_read(&tty->termios_rwsem);

				tty_flush_to_ldisc(tty);

				down_read(&tty->termios_rwsem);

				if (!input_available_p(tty, 0)) {

				retval = -EIO;

				break;

			}

			} else {

			if (tty_hung_up_p(file))

				break;

			if (!timeout)
@@ -2225,7 +2220,6 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, 
			down_read(&tty->termios_rwsem);

			continue;

		}

		}

		__set_current_state(TASK_RUNNING);



		if (ldata->icanon && !L_EXTPROC(tty)) {

drivers/tty/pty.c

+1 −0
Original line number Diff line number Diff line
@@ -53,6 +53,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp) 
	/* Review - krefs on tty_link ?? */

	if (!tty->link)

		return;

	tty_flush_to_ldisc(tty->link);

	set_bit(TTY_OTHER_CLOSED, &tty->link->flags);

	wake_up_interruptible(&tty->link->read_wait);

	wake_up_interruptible(&tty->link->write_wait);