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Commit a19d0c6a authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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n_tty: Split n_tty_chars_in_buffer() for reader-only interface 



N_TTY .chars_in_buffer() method requires serialized access if
the current thread is not the single-consumer, n_tty_read().

Separate the internal interface; prepare for lockless read-side.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 32f13521

drivers/tty/n_tty.c

+8 −3
Original line number Diff line number Diff line
@@ -277,7 +277,7 @@ static void n_tty_flush_buffer(struct tty_struct *tty) 
 *	Locking: read_lock

 */



static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)

static ssize_t chars_in_buffer(struct tty_struct *tty)

{

	struct n_tty_data *ldata = tty->disc_data;

	unsigned long flags;
@@ -295,6 +295,11 @@ static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty) 
	return n;

}



static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)

{

	return chars_in_buffer(tty);

}



/**

 *	is_utf8_continuation	-	utf8 multibyte check

 *	@c: byte to check
@@ -2032,7 +2037,7 @@ do_it_again: 
		}



		/* If there is enough space in the read buffer now, let the

		 * low-level driver know. We use n_tty_chars_in_buffer() to

		 * low-level driver know. We use chars_in_buffer() to

		 * check the buffer, as it now knows about canonical mode.

		 * Otherwise, if the driver is throttled and the line is

		 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
@@ -2040,7 +2045,7 @@ do_it_again: 
		 */

		while (1) {

			tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);

			if (n_tty_chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)

			if (chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)

				break;

			if (!tty->count)

				break;