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: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
drivers/tty/n_tty.c | 15 ++-------------
1 file changed, 2 insertions(+), 13 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 2b38bb2..f777ec6 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -101,7 +101,6 @@ 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;
@@ -120,7 +119,7 @@ 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)
@@ -220,7 +219,6 @@ 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++;
}
}
@@ -261,7 +259,7 @@ 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);
@@ -965,16 +963,12 @@ 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);
@@ -1012,7 +1006,6 @@ 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)) {
@@ -1471,7 +1464,6 @@ static void n_tty_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;
@@ -1480,7 +1472,6 @@ static void n_tty_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++) {
@@ -1760,7 +1751,6 @@ 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;
@@ -1848,7 +1838,6 @@ 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:
--
1.8.1.2
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
