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Commit 862eeffe authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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n_tty: Replace echo_cnt with computed value 



Prepare for lockless echo_buf handling; compute current byte count
of echo_buf from head and tail indices.

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

drivers/tty/n_tty.c

+7 −13
Original line number Diff line number Diff line
@@ -110,7 +110,6 @@ struct n_tty_data { 
	unsigned char *echo_buf;

	size_t echo_head;

	size_t echo_tail;

	unsigned int echo_cnt;



	/* protected by output lock */

	unsigned int column;
@@ -336,7 +335,7 @@ static void reset_buffer_flags(struct n_tty_data *ldata) 
	ldata->read_head = ldata->canon_head = ldata->read_tail = 0;



	mutex_lock(&ldata->echo_lock);

	ldata->echo_head = ldata->echo_tail = ldata->echo_cnt = 0;

	ldata->echo_head = ldata->echo_tail  = 0;

	mutex_unlock(&ldata->echo_lock);



	ldata->erasing = 0;
@@ -654,7 +653,7 @@ static void process_echoes(struct tty_struct *tty) 
	size_t tail;

	unsigned char c;



	if (!ldata->echo_cnt)

	if (ldata->echo_head == ldata->echo_tail)

		return;



	mutex_lock(&ldata->output_lock);
@@ -663,7 +662,7 @@ static void process_echoes(struct tty_struct *tty) 
	space = tty_write_room(tty);



	tail = ldata->echo_tail;

	nr = ldata->echo_cnt;

	nr = ldata->echo_head - ldata->echo_tail;

	while (nr > 0) {

		c = echo_buf(ldata, tail);

		if (c == ECHO_OP_START) {
@@ -779,7 +778,6 @@ static void process_echoes(struct tty_struct *tty) 
	}



	ldata->echo_tail = tail;

	ldata->echo_cnt = nr;



	mutex_unlock(&ldata->echo_lock);

	mutex_unlock(&ldata->output_lock);
@@ -800,24 +798,20 @@ static void process_echoes(struct tty_struct *tty) 


static void add_echo_byte(unsigned char c, struct n_tty_data *ldata)

{

	if (ldata->echo_cnt == N_TTY_BUF_SIZE) {

	if (ldata->echo_head - ldata->echo_tail == N_TTY_BUF_SIZE) {

		size_t head = ldata->echo_head;

		/*

		 * Since the buffer start position needs to be advanced,

		 * be sure to step by a whole operation byte group.

		 */

		if (echo_buf(ldata, head) == ECHO_OP_START) {

			if (echo_buf(ldata, head + 1) == ECHO_OP_ERASE_TAB) {

			if (echo_buf(ldata, head + 1) == ECHO_OP_ERASE_TAB)

				ldata->echo_tail += 3;

				ldata->echo_cnt -= 2;

			} else {

			else

				ldata->echo_tail += 2;

				ldata->echo_cnt -= 1;

			}

		} else

			ldata->echo_tail++;

	} else

		ldata->echo_cnt++;

	}



	*echo_buf_addr(ldata, ldata->echo_head++) = c;

}