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Code Issues Releases Wiki Activity

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: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2013-06-15 09:14:22 -04:00 committed by Greg Kroah-Hartman
parent bc5a5e3f45
commit a2f73be8ee
1 changed files with 2 additions and 13 deletions
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15
drivers/tty/n_tty.c
View File

@ -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: