Prepare for lockless echo_buf handling; compute current byte count
of echo_buf from head and tail indices.
Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
---
drivers/tty/n_tty.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index f90e171..68dc9fd 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -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;
@@ -335,7 +334,7 @@ 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;
@@ -653,7 +652,7 @@ 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);
@@ -662,7 +661,7 @@ 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) {
@@ -778,7 +777,6 @@ 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);
@@ -799,24 +797,20 @@ 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;
}
--
1.8.1.2
--
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