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Commit a2f73be8 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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n_tty: Remove read_cnt 



Storing the read_cnt creates an unnecessary shared variable
between the single-producer (n_tty_receive_buf()) and the
single-consumer (n_tty_read()).

Compute read_cnt from head & tail instead of storing.

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bc5a5e3f

drivers/tty/n_tty.c

+2 −13
Original line number Diff line number Diff line
@@ -98,7 +98,6 @@ struct n_tty_data { 
	char *read_buf;

	size_t read_head;

	size_t read_tail;

	int read_cnt;

	int minimum_to_wake;



	unsigned char *echo_buf;
@@ -117,7 +116,7 @@ struct n_tty_data { 


static inline size_t read_cnt(struct n_tty_data *ldata)

{

	return ldata->read_cnt;

	return ldata->read_head - ldata->read_tail;

}



static inline unsigned char read_buf(struct n_tty_data *ldata, size_t i)
@@ -198,7 +197,6 @@ static void put_tty_queue_nolock(unsigned char c, struct n_tty_data *ldata) 
	if (read_cnt(ldata) < N_TTY_BUF_SIZE) {

		*read_buf_addr(ldata, ldata->read_head) = c;

		ldata->read_head++;

		ldata->read_cnt++;

	}

}
@@ -239,7 +237,7 @@ static void reset_buffer_flags(struct n_tty_data *ldata) 
	unsigned long flags;



	raw_spin_lock_irqsave(&ldata->read_lock, flags);

	ldata->read_head = ldata->read_tail = ldata->read_cnt = 0;

	ldata->read_head = ldata->read_tail = 0;

	raw_spin_unlock_irqrestore(&ldata->read_lock, flags);



	mutex_lock(&ldata->echo_lock);
@@ -942,16 +940,12 @@ static void eraser(unsigned char c, struct tty_struct *tty) 
	else {

		if (!L_ECHO(tty)) {

			raw_spin_lock_irqsave(&ldata->read_lock, flags);

			ldata->read_cnt -= ((ldata->read_head - ldata->canon_head) &

					  (N_TTY_BUF_SIZE - 1));

			ldata->read_head = ldata->canon_head;

			raw_spin_unlock_irqrestore(&ldata->read_lock, flags);

			return;

		}

		if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {

			raw_spin_lock_irqsave(&ldata->read_lock, flags);

			ldata->read_cnt -= ((ldata->read_head - ldata->canon_head) &

					  (N_TTY_BUF_SIZE - 1));

			ldata->read_head = ldata->canon_head;

			raw_spin_unlock_irqrestore(&ldata->read_lock, flags);

			finish_erasing(ldata);
@@ -989,7 +983,6 @@ static void eraser(unsigned char c, struct tty_struct *tty) 
		cnt = ldata->read_head - head;

		raw_spin_lock_irqsave(&ldata->read_lock, flags);

		ldata->read_head = head;

		ldata->read_cnt -= cnt;

		raw_spin_unlock_irqrestore(&ldata->read_lock, flags);

		if (L_ECHO(tty)) {

			if (L_ECHOPRT(tty)) {
@@ -1448,7 +1441,6 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp, 
		i = min(count, i);

		memcpy(read_buf_addr(ldata, ldata->read_head), cp, i);

		ldata->read_head += i;

		ldata->read_cnt += i;

		cp += i;

		count -= i;
@@ -1457,7 +1449,6 @@ static void __receive_buf(struct tty_struct *tty, const unsigned char *cp, 
		i = min(count, i);

		memcpy(read_buf_addr(ldata, ldata->read_head), cp, i);

		ldata->read_head += i;

		ldata->read_cnt += i;

		raw_spin_unlock_irqrestore(&ldata->read_lock, cpuflags);

	} else {

		for (i = count, p = cp, f = fp; i; i--, p++) {
@@ -1762,7 +1753,6 @@ static int copy_from_read_buf(struct tty_struct *tty, 
				ldata->icanon);

		raw_spin_lock_irqsave(&ldata->read_lock, flags);

		ldata->read_tail += n;

		ldata->read_cnt -= n;

		/* Turn single EOF into zero-length read */

		if (L_EXTPROC(tty) && ldata->icanon && is_eof && !read_cnt(ldata))

			n = 0;
@@ -1850,7 +1840,6 @@ static int canon_copy_from_read_buf(struct tty_struct *tty, 


	raw_spin_lock_irqsave(&ldata->read_lock, flags);

	ldata->read_tail += c;

	ldata->read_cnt -= c;

	if (found) {

		__clear_bit(eol, ldata->read_flags);

		/* this test should be redundant: