Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 76bc35e7 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
Browse files

tty: Fix ldisc halt sequence on hangup 



Flip buffer work cannot be cancelled until all outstanding ldisc
references have been released. Convert the ldisc ref wait into
a full ldisc halt with buffer work cancellation.

Note that the legacy mutex is not held while cancelling.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2276ad97

drivers/tty/tty_ldisc.c

+19 −20
Original line number Diff line number Diff line
@@ -551,22 +551,30 @@ static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout) 
}



/**

 *	tty_ldisc_hangup_wait_idle - wait for the ldisc to become idle

 *	@tty: tty to wait for

 *

 *	Wait for the line discipline to become idle. The discipline must

 *	have been halted for this to guarantee it remains idle.

 *	tty_ldisc_hangup_halt - halt the line discipline for hangup

 *	@tty: tty being hung up

 *

 *	Shut down the line discipline and work queue for the tty device

 *	being hungup. Clear the TTY_LDISC flag to ensure no further

 *	references can be obtained, wait for remaining references to be

 *	released, and cancel pending buffer work to ensure no more

 *	data is fed to this ldisc.

 *	Caller must hold legacy and ->ldisc_mutex.

 *

 *	NB: tty_set_ldisc() is prevented from changing the ldisc concurrently

 *	with this function by checking the TTY_HUPPING flag.

 *

 *	NB: if tty->ldisc is NULL then buffer work does not need to be

 *	cancelled because it must already have done as a precondition

 *	of closing the ldisc and setting tty->ldisc to NULL

 */

static bool tty_ldisc_hangup_wait_idle(struct tty_struct *tty)

static bool tty_ldisc_hangup_halt(struct tty_struct *tty)

{

	char cur_n[TASK_COMM_LEN], tty_n[64];

	long timeout = 3 * HZ;



	clear_bit(TTY_LDISC, &tty->flags);



	if (tty->ldisc) {	/* Not yet closed */

		tty_unlock(tty);
@@ -577,6 +585,10 @@ static bool tty_ldisc_hangup_wait_idle(struct tty_struct *tty) 
				__func__, get_task_comm(cur_n, current),

				tty_name(tty, tty_n));

		}



		cancel_work_sync(&tty->port->buf.work);

		set_bit(TTY_LDISC_HALTED, &tty->flags);



		/* must reacquire both locks and preserve lock order */

		mutex_unlock(&tty->ldisc_mutex);

		tty_lock(tty);
@@ -851,24 +863,11 @@ void tty_ldisc_hangup(struct tty_struct *tty) 
	 */

	mutex_lock(&tty->ldisc_mutex);



	/*

	 * this is like tty_ldisc_halt, but we need to give up

	 * the BTM before calling cancel_work_sync, which may

	 * need to wait for another function taking the BTM

	 */

	clear_bit(TTY_LDISC, &tty->flags);

	tty_unlock(tty);

	cancel_work_sync(&tty->port->buf.work);

	set_bit(TTY_LDISC_HALTED, &tty->flags);

	mutex_unlock(&tty->ldisc_mutex);

	tty_lock(tty);

	mutex_lock(&tty->ldisc_mutex);



	/* At this point we have a closed ldisc and we want to

	   reopen it. We could defer this to the next open but

	   it means auditing a lot of other paths so this is

	   a FIXME */

	if (tty_ldisc_hangup_wait_idle(tty)) {

	if (tty_ldisc_hangup_halt(tty)) {

		if (reset == 0) {



			if (!tty_ldisc_reinit(tty, tty->termios.c_line))