Commit 2c3bb20f authored by Paul Fulghum's avatar Paul Fulghum Committed by Linus Torvalds
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[PATCH] add receive_room flow control to flush_to_ldisc 



Flush data serially to line discipline in blocks no larger than
tty->receive_room to avoid losing data if line discipline is busy (such as
N_TTY operating at high speed on heavily loaded system) or does not accept
data in large blocks (such as N_MOUSE).

Signed-off-by: default avatarPaul Fulghum <paulkf@microgate.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 817d6d3b

drivers/char/tty_io.c

+24 −13
Original line number Diff line number Diff line
@@ -2771,8 +2771,7 @@ static void flush_to_ldisc(void *private_) 
	struct tty_struct *tty = (struct tty_struct *) private_;

	unsigned long 	flags;

	struct tty_ldisc *disc;

	struct tty_buffer *tbuf;

	int count;

	struct tty_buffer *tbuf, *head;

	char *char_buf;

	unsigned char *flag_buf;
@@ -2781,21 +2780,33 @@ static void flush_to_ldisc(void *private_) 
		return;



	spin_lock_irqsave(&tty->buf.lock, flags);

	while((tbuf = tty->buf.head) != NULL) {

		while ((count = tbuf->commit - tbuf->read) != 0) {

			char_buf = tbuf->char_buf_ptr + tbuf->read;

			flag_buf = tbuf->flag_buf_ptr + tbuf->read;

			tbuf->read += count;

	head = tty->buf.head;

	if (head != NULL) {

		tty->buf.head = NULL;

		for (;;) {

			int count = head->commit - head->read;

			if (!count) {

				if (head->next == NULL)

					break;

				tbuf = head;

				head = head->next;

				tty_buffer_free(tty, tbuf);

				continue;

			}

			if (!tty->receive_room) {

				schedule_delayed_work(&tty->buf.work, 1);

				break;

			}

			if (count > tty->receive_room)

				count = tty->receive_room;

			char_buf = head->char_buf_ptr + head->read;

			flag_buf = head->flag_buf_ptr + head->read;

			head->read += count;

			spin_unlock_irqrestore(&tty->buf.lock, flags);

			disc->receive_buf(tty, char_buf, flag_buf, count);

			spin_lock_irqsave(&tty->buf.lock, flags);

		}

		if (tbuf->active)

			break;

		tty->buf.head = tbuf->next;

		if (tty->buf.head == NULL)

			tty->buf.tail = NULL;

		tty_buffer_free(tty, tbuf);

		tty->buf.head = head;

	}

	spin_unlock_irqrestore(&tty->buf.lock, flags);