Exemple #1
0
static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
{
	char buf[64];
	struct tty_ldisc new_ldisc;

	/* There is an outstanding reference here so this is safe */
	tty_ldisc_get(old->ops->num, old);
	tty_ldisc_assign(tty, old);
	tty_set_termios_ldisc(tty, old->ops->num);
	if (old->ops->open && (old->ops->open(tty) < 0)) {
		tty_ldisc_put(old->ops);
		/* This driver is always present */
		if (tty_ldisc_get(N_TTY, &new_ldisc) < 0)
			panic("n_tty: get");
		tty_ldisc_assign(tty, &new_ldisc);
		tty_set_termios_ldisc(tty, N_TTY);
		if (new_ldisc.ops->open) {
			int r = new_ldisc.ops->open(tty);
				if (r < 0)
				panic("Couldn't open N_TTY ldisc for "
				      "%s --- error %d.",
				      tty_name(tty, buf), r);
		}
	}
}
Exemple #2
0
static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
{
	char buf[64];
	struct tty_ldisc *new_ldisc;
	int r;

	/* There is an outstanding reference here so this is safe */
	old = tty_ldisc_get(old->ops->num);
	WARN_ON(IS_ERR(old));
	tty_ldisc_assign(tty, old);
	tty_set_termios_ldisc(tty, old->ops->num);
	if (tty_ldisc_open(tty, old) < 0) {
		tty_ldisc_put(old);
		/* This driver is always present */
		new_ldisc = tty_ldisc_get(N_TTY);
		if (IS_ERR(new_ldisc))
			panic("n_tty: get");
		tty_ldisc_assign(tty, new_ldisc);
		tty_set_termios_ldisc(tty, N_TTY);
		r = tty_ldisc_open(tty, new_ldisc);
		if (r < 0)
			panic("Couldn't open N_TTY ldisc for "
			      "%s --- error %d.",
			      tty_name(tty, buf), r);
	}
}
Exemple #3
0
void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
{
	unsigned long flags;
	struct tty_ldisc ld;
	/*
	 * Prevent flush_to_ldisc() from rescheduling the work for later.  Then
	 * kill any delayed work. As this is the final close it does not
	 * race with the set_ldisc code path.
	 */
	clear_bit(TTY_LDISC, &tty->flags);
	cancel_delayed_work(&tty->buf.work);

	/*
	 * Wait for ->hangup_work and ->buf.work handlers to terminate
	 */

	flush_scheduled_work();

	/*
	 * Wait for any short term users (we know they are just driver
	 * side waiters as the file is closing so user count on the file
	 * side is zero.
	 */
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	while (tty->ldisc.refcount) {
		spin_unlock_irqrestore(&tty_ldisc_lock, flags);
		wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0);
		spin_lock_irqsave(&tty_ldisc_lock, flags);
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	/*
	 * Shutdown the current line discipline, and reset it to N_TTY.
	 *
	 * FIXME: this MUST get fixed for the new reflocking
	 */
	if (tty->ldisc.ops->close)
		(tty->ldisc.ops->close)(tty);
	tty_ldisc_put(tty->ldisc.ops);

	/*
	 *	Switch the line discipline back
	 */
	WARN_ON(tty_ldisc_get(N_TTY, &ld));
	tty_ldisc_assign(tty, &ld);
	tty_set_termios_ldisc(tty, N_TTY);
	if (o_tty) {
		/* FIXME: could o_tty be in setldisc here ? */
		clear_bit(TTY_LDISC, &o_tty->flags);
		if (o_tty->ldisc.ops->close)
			(o_tty->ldisc.ops->close)(o_tty);
		tty_ldisc_put(o_tty->ldisc.ops);
		WARN_ON(tty_ldisc_get(N_TTY, &ld));
		tty_ldisc_assign(o_tty, &ld);
		tty_set_termios_ldisc(o_tty, N_TTY);
	}
}
Exemple #4
0
void tty_ldisc_init(struct tty_struct *tty)
{
	struct tty_ldisc ld;
	if (tty_ldisc_get(N_TTY, &ld) < 0)
		panic("n_tty: init_tty");
	tty_ldisc_assign(tty, &ld);
}
Exemple #5
0
void tty_ldisc_init(struct tty_struct *tty)
{
	struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
	if (IS_ERR(ld))
		panic("n_tty: init_tty");
	tty_ldisc_assign(tty, ld);
}
Exemple #6
0
static void tty_ldisc_reinit(struct tty_struct *tty)
{
	struct tty_ldisc *ld;

	tty_ldisc_close(tty, tty->ldisc);
	tty_ldisc_put(tty->ldisc);
	tty->ldisc = NULL;
	/*
	 *	Switch the line discipline back
	 */
	ld = tty_ldisc_get(N_TTY);
	BUG_ON(IS_ERR(ld));
	tty_ldisc_assign(tty, ld);
	tty_set_termios_ldisc(tty, N_TTY);
}
Exemple #7
0
static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
{
	struct tty_ldisc *ld = tty_ldisc_get(ldisc);

	if (IS_ERR(ld))
		return -1;

	tty_ldisc_close(tty, tty->ldisc);
	tty_ldisc_put(tty->ldisc);
	tty->ldisc = NULL;
	/*
	 *	Switch the line discipline back
	 */
	tty_ldisc_assign(tty, ld);
	tty_set_termios_ldisc(tty, ldisc);

	return 0;
}
Exemple #8
0
static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
#else
//static void tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
#endif
//20110402 [email protected] [LS855] handle exception for tty daemon [END]
{

//20110402 [email protected] [LS855] handle exception for tty daemon [START]
#if 1
	struct tty_ldisc *ld = tty_ldisc_get(ldisc); 
#else
//	struct tty_ldisc *ld;
#endif
//20110402 [email protected] [LS855] handle exception for tty daemon [END]

	 if (IS_ERR(ld)) 
		 return -1; 

	tty_ldisc_close(tty, tty->ldisc);
	tty_ldisc_put(tty->ldisc);
	tty->ldisc = NULL;
	/*
	 *	Switch the line discipline back
	 */
//20110402 [email protected] [LS855] handle exception for tty daemon [START]	 
#if 0	 
	ld = tty_ldisc_get(ldisc);
	BUG_ON(IS_ERR(ld));
#endif
//20110402 [email protected] [LS855] handle exception for tty daemon [END]


	tty_ldisc_assign(tty, ld);
	tty_set_termios_ldisc(tty, ldisc);

	return 0;  //20110402 [email protected] [LS855] handle exception for tty daemon
}
Exemple #9
0
int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
	int retval;
	struct tty_ldisc o_ldisc, new_ldisc;
	int work;
	unsigned long flags;
	struct tty_struct *o_tty;

restart:
	/* This is a bit ugly for now but means we can break the 'ldisc
	   is part of the tty struct' assumption later */
	retval = tty_ldisc_get(ldisc, &new_ldisc);
	if (retval)
		return retval;

	/*
	 *	Problem: What do we do if this blocks ?
	 */

	tty_wait_until_sent(tty, 0);

	if (tty->ldisc.ops->num == ldisc) {
		tty_ldisc_put(new_ldisc.ops);
		return 0;
	}

	/*
	 *	No more input please, we are switching. The new ldisc
	 *	will update this value in the ldisc open function
	 */

	tty->receive_room = 0;

	o_ldisc = tty->ldisc;
	o_tty = tty->link;

	/*
	 *	Make sure we don't change while someone holds a
	 *	reference to the line discipline. The TTY_LDISC bit
	 *	prevents anyone taking a reference once it is clear.
	 *	We need the lock to avoid racing reference takers.
	 *
	 *	We must clear the TTY_LDISC bit here to avoid a livelock
	 *	with a userspace app continually trying to use the tty in
	 *	parallel to the change and re-referencing the tty.
	 */
	clear_bit(TTY_LDISC, &tty->flags);
	if (o_tty)
		clear_bit(TTY_LDISC, &o_tty->flags);

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if (tty->ldisc.refcount || (o_tty && o_tty->ldisc.refcount)) {
		if (tty->ldisc.refcount) {
			/* Free the new ldisc we grabbed. Must drop the lock
			   first. */
			spin_unlock_irqrestore(&tty_ldisc_lock, flags);
			tty_ldisc_put(new_ldisc.ops);
			/*
			 * There are several reasons we may be busy, including
			 * random momentary I/O traffic. We must therefore
			 * retry. We could distinguish between blocking ops
			 * and retries if we made tty_ldisc_wait() smarter.
			 * That is up for discussion.
			 */
			if (wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0)
				return -ERESTARTSYS;
			goto restart;
		}
		if (o_tty && o_tty->ldisc.refcount) {
			spin_unlock_irqrestore(&tty_ldisc_lock, flags);
			tty_ldisc_put(o_tty->ldisc.ops);
			if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0)
				return -ERESTARTSYS;
			goto restart;
		}
	}
	/*
	 *	If the TTY_LDISC bit is set, then we are racing against
	 *	another ldisc change
	 */
	if (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
		struct tty_ldisc *ld;
		spin_unlock_irqrestore(&tty_ldisc_lock, flags);
		tty_ldisc_put(new_ldisc.ops);
		ld = tty_ldisc_ref_wait(tty);
		tty_ldisc_deref(ld);
		goto restart;
	}
	/*
	 *	This flag is used to avoid two parallel ldisc changes. Once
	 *	open and close are fine grained locked this may work better
	 *	as a mutex shared with the open/close/hup paths
	 */
	set_bit(TTY_LDISC_CHANGING, &tty->flags);
	if (o_tty)
		set_bit(TTY_LDISC_CHANGING, &o_tty->flags);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	
	/*
	 *	From this point on we know nobody has an ldisc
	 *	usage reference, nor can they obtain one until
	 *	we say so later on.
	 */

	work = cancel_delayed_work(&tty->buf.work);
	/*
	 * Wait for ->hangup_work and ->buf.work handlers to terminate
	 * MUST NOT hold locks here.
	 */
	flush_scheduled_work();
	/* Shutdown the current discipline. */
	if (o_ldisc.ops->close)
		(o_ldisc.ops->close)(tty);

	/* Now set up the new line discipline. */
	tty_ldisc_assign(tty, &new_ldisc);
	tty_set_termios_ldisc(tty, ldisc);
	if (new_ldisc.ops->open)
		retval = (new_ldisc.ops->open)(tty);
	if (retval < 0) {
		tty_ldisc_put(new_ldisc.ops);
		tty_ldisc_restore(tty, &o_ldisc);
	}
	/* At this point we hold a reference to the new ldisc and a
	   a reference to the old ldisc. If we ended up flipping back
	   to the existing ldisc we have two references to it */

	if (tty->ldisc.ops->num != o_ldisc.ops->num && tty->ops->set_ldisc)
		tty->ops->set_ldisc(tty);

	tty_ldisc_put(o_ldisc.ops);

	/*
	 *	Allow ldisc referencing to occur as soon as the driver
	 *	ldisc callback completes.
	 */

	tty_ldisc_enable(tty);
	if (o_tty)
		tty_ldisc_enable(o_tty);

	/* Restart it in case no characters kick it off. Safe if
	   already running */
	if (work)
		schedule_delayed_work(&tty->buf.work, 1);
	return retval;
}
Exemple #10
0
int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
	int retval;
	struct tty_ldisc *o_ldisc, *new_ldisc;
	int work, o_work = 0;
	struct tty_struct *o_tty;

	new_ldisc = tty_ldisc_get(ldisc);
	if (IS_ERR(new_ldisc))
		return PTR_ERR(new_ldisc);

	/*
	 *	We need to look at the tty locking here for pty/tty pairs
	 *	when both sides try to change in parallel.
	 */

	o_tty = tty->link;	/* o_tty is the pty side or NULL */


	/*
	 *	Check the no-op case
	 */

	if (tty->ldisc->ops->num == ldisc) {
		tty_ldisc_put(new_ldisc);
		return 0;
	}

	/*
	 *	Problem: What do we do if this blocks ?
	 *	We could deadlock here
	 */

	tty_wait_until_sent(tty, 0);

	mutex_lock(&tty->ldisc_mutex);

	/*
	 *	We could be midstream of another ldisc change which has
	 *	dropped the lock during processing. If so we need to wait.
	 */

	while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
		mutex_unlock(&tty->ldisc_mutex);
		wait_event(tty_ldisc_wait,
			test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
		mutex_lock(&tty->ldisc_mutex);
	}
	set_bit(TTY_LDISC_CHANGING, &tty->flags);

	/*
	 *	No more input please, we are switching. The new ldisc
	 *	will update this value in the ldisc open function
	 */

	tty->receive_room = 0;

	o_ldisc = tty->ldisc;
	/*
	 *	Make sure we don't change while someone holds a
	 *	reference to the line discipline. The TTY_LDISC bit
	 *	prevents anyone taking a reference once it is clear.
	 *	We need the lock to avoid racing reference takers.
	 *
	 *	We must clear the TTY_LDISC bit here to avoid a livelock
	 *	with a userspace app continually trying to use the tty in
	 *	parallel to the change and re-referencing the tty.
	 */

	work = tty_ldisc_halt(tty);
	if (o_tty)
		o_work = tty_ldisc_halt(o_tty);

	/*
	 * Wait for ->hangup_work and ->buf.work handlers to terminate.
	 * We must drop the mutex here in case a hangup is also in process.
	 */

	mutex_unlock(&tty->ldisc_mutex);

	flush_scheduled_work();

	mutex_lock(&tty->ldisc_mutex);
	if (test_bit(TTY_HUPPED, &tty->flags)) {
		/* We were raced by the hangup method. It will have stomped
		   the ldisc data and closed the ldisc down */
		clear_bit(TTY_LDISC_CHANGING, &tty->flags);
		mutex_unlock(&tty->ldisc_mutex);
		tty_ldisc_put(new_ldisc);
		return -EIO;
	}

	/* Shutdown the current discipline. */
	tty_ldisc_close(tty, o_ldisc);

	/* Now set up the new line discipline. */
	tty_ldisc_assign(tty, new_ldisc);
	tty_set_termios_ldisc(tty, ldisc);

	retval = tty_ldisc_open(tty, new_ldisc);
	if (retval < 0) {
		/* Back to the old one or N_TTY if we can't */
		tty_ldisc_put(new_ldisc);
		tty_ldisc_restore(tty, o_ldisc);
	}

	/* At this point we hold a reference to the new ldisc and a
	   a reference to the old ldisc. If we ended up flipping back
	   to the existing ldisc we have two references to it */

	if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
		tty->ops->set_ldisc(tty);

	tty_ldisc_put(o_ldisc);

	/*
	 *	Allow ldisc referencing to occur again
	 */

	tty_ldisc_enable(tty);
	if (o_tty)
		tty_ldisc_enable(o_tty);

	/* Restart the work queue in case no characters kick it off. Safe if
	   already running */
	if (work)
		schedule_delayed_work(&tty->buf.work, 1);
	if (o_work)
		schedule_delayed_work(&o_tty->buf.work, 1);
	mutex_unlock(&tty->ldisc_mutex);
	return retval;
}
Exemple #11
0
/**
 *	tty_ldisc_init		-	ldisc cleanup for new tty
 *	@tty: tty that was allocated recently
 *
 *	The tty structure must not becompletely set up (tty_ldisc_setup) when
 *      this call is made.
 */
void tty_ldisc_deinit(struct tty_struct *tty)
{
	put_ldisc(tty->ldisc);
	tty_ldisc_assign(tty, NULL);
}