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Commit 21622939 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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tty: Add diagnostic for halted line discipline 



Flip buffer work must not be scheduled by the line discipline
after the line discipline has been halted; issue warning.

Note: drivers can still schedule flip buffer work.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 91debb03

drivers/tty/n_tty.c

+8 −0
Original line number Diff line number Diff line
@@ -153,6 +153,12 @@ static void n_tty_set_room(struct tty_struct *tty) 
	if (left && !old_left) {

		WARN_RATELIMIT(tty->port->itty == NULL,

				"scheduling with invalid itty\n");

		/* see if ldisc has been killed - if so, this means that

		 * even though the ldisc has been halted and ->buf.work

		 * cancelled, ->buf.work is about to be rescheduled

		 */

		WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),

			       "scheduling buffer work for halted ldisc\n");

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

	}

}
@@ -1624,6 +1630,8 @@ static int n_tty_open(struct tty_struct *tty) 
		goto err_free_bufs;



	tty->disc_data = ldata;

	/* indicate buffer work may resume */

	clear_bit(TTY_LDISC_HALTED, &tty->flags);

	reset_buffer_flags(tty);

	tty_unthrottle(tty);

	ldata->column = 0;

drivers/tty/tty_ldisc.c

+6 −1
Original line number Diff line number Diff line
@@ -375,6 +375,7 @@ static inline void tty_ldisc_put(struct tty_ldisc *ld) 


void tty_ldisc_enable(struct tty_struct *tty)

{

	clear_bit(TTY_LDISC_HALTED, &tty->flags);

	set_bit(TTY_LDISC, &tty->flags);

	clear_bit(TTY_LDISC_CHANGING, &tty->flags);

	wake_up(&tty_ldisc_wait);
@@ -513,8 +514,11 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) 


static int tty_ldisc_halt(struct tty_struct *tty)

{

	int scheduled;

	clear_bit(TTY_LDISC, &tty->flags);

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

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

	set_bit(TTY_LDISC_HALTED, &tty->flags);

	return scheduled;

}



/**
@@ -820,6 +824,7 @@ void tty_ldisc_hangup(struct tty_struct *tty) 
	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);

retry:

	tty_lock(tty);

include/linux/tty.h

+1 −0
Original line number Diff line number Diff line
@@ -315,6 +315,7 @@ struct tty_file_private { 
#define TTY_NO_WRITE_SPLIT 	17	/* Preserve write boundaries to driver */

#define TTY_HUPPED 		18	/* Post driver->hangup() */

#define TTY_HUPPING 		21	/* ->hangup() in progress */

#define TTY_LDISC_HALTED	22	/* Line discipline is halted */



#define TTY_WRITE_FLUSH(tty) tty_write_flush((tty))