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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: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2013-06-15 10:04:23 -04:00 committed by Greg Kroah-Hartman
parent addaebccf6
commit 862eeffef1
1 changed files with 7 additions and 13 deletions
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20
drivers/tty/n_tty.c
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@ -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;
}