Unverified Commit 84045b79 authored by openeuler-ci-bot's avatar openeuler-ci-bot Committed by Gitee
Browse files

!8301 tty: fix hang on tty device with no_room set 

Merge Pull Request from: @ci-robot 
 
PR sync from: Yi Yang <yiyang13@huawei.com>
https://mailweb.openeuler.org/hyperkitty/list/kernel@openeuler.org/message/KOBFTG2FFVBPSWWJ3XAH5XUBYO2DTG44/ 
 
https://gitee.com/openeuler/kernel/issues/I9T85S 
 
Link:https://gitee.com/openeuler/kernel/pulls/8301

 

Reviewed-by: default avatarZhang Changzhong <zhangchangzhong@huawei.com>
Reviewed-by: default avatarLiu YongQiang <liuyongqiang13@huawei.com>
Signed-off-by: default avatarZhang Changzhong <zhangchangzhong@huawei.com>
parents 80cb8105 ff7a1d2f

drivers/tty/n_tty.c

+21 −4
Original line number Diff line number Diff line
@@ -204,8 +204,8 @@ static void n_tty_kick_worker(struct tty_struct *tty) 
	struct n_tty_data *ldata = tty->disc_data;



	/* Did the input worker stop? Restart it */

	if (unlikely(ldata->no_room)) {

		ldata->no_room = 0;

	if (unlikely(READ_ONCE(ldata->no_room))) {

		WRITE_ONCE(ldata->no_room, 0);



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

				"scheduling with invalid itty\n");
@@ -1727,7 +1727,7 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp, 
			if (overflow && room < 0)

				ldata->read_head--;

			room = overflow;

			ldata->no_room = flow && !room;

			WRITE_ONCE(ldata->no_room, flow && !room);

		} else

			overflow = 0;
@@ -1758,6 +1758,17 @@ n_tty_receive_buf_common(struct tty_struct *tty, const unsigned char *cp, 
	} else

		n_tty_check_throttle(tty);



	if (unlikely(ldata->no_room)) {

		/*

		 * Barrier here is to ensure to read the latest read_tail in

		 * chars_in_buffer() and to make sure that read_tail is not loaded

		 * before ldata->no_room is set.

		 */

		smp_mb();

		if (!chars_in_buffer(tty))

			n_tty_kick_worker(tty);

	}



	up_read(&tty->termios_rwsem);



	return rcvd;
@@ -2261,8 +2272,14 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, 
		if (time)

			timeout = time;

	}

	if (tail != ldata->read_tail)

	if (tail != ldata->read_tail) {

		/*

		 * Make sure no_room is not read in n_tty_kick_worker()

		 * before setting ldata->read_tail in copy_from_read_buf().

		 */

		smp_mb();

		n_tty_kick_worker(tty);

	}

	up_read(&tty->termios_rwsem);



	remove_wait_queue(&tty->read_wait, &wait);