[PATCH 3.12 008/144] n_tty: Fix apparent order of echoed output

From: Greg Kroah-Hartman
Date: Mon Jan 06 2014 - 19:14:52 EST


3.12-stable review patch. If anyone has any objections, please let me know.

------------------

From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>

commit 1075a6e2dc7e2a96efc417b98dd98f57fdae985d upstream.

With block processing of echoed output, observed output order is still
required. Push completed echoes and echo commands prior to output.

Introduce echo_mark echo buffer index, which tracks completed echo
commands; ie., those submitted via commit_echoes but which may not
have been committed. Ensure that completed echoes are output prior
to subsequent terminal writes in process_echoes().

Fixes newline/prompt output order in cooked mode shell.

Reported-by: Karl Dahlke <eklhad@xxxxxxxxxxx>
Reported-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Tested-by: Karl Dahlke <eklhad@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/tty/n_tty.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -93,6 +93,7 @@ struct n_tty_data {
size_t canon_head;
size_t echo_head;
size_t echo_commit;
+ size_t echo_mark;
DECLARE_BITMAP(char_map, 256);

/* private to n_tty_receive_overrun (single-threaded) */
@@ -336,6 +337,7 @@ static void reset_buffer_flags(struct n_
{
ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
+ ldata->echo_mark = 0;
ldata->line_start = 0;

ldata->erasing = 0;
@@ -787,6 +789,7 @@ static void commit_echoes(struct tty_str
size_t head;

head = ldata->echo_head;
+ ldata->echo_mark = head;
old = ldata->echo_commit - ldata->echo_tail;

/* Process committed echoes if the accumulated # of bytes
@@ -811,10 +814,11 @@ static void process_echoes(struct tty_st
size_t echoed;

if ((!L_ECHO(tty) && !L_ECHONL(tty)) ||
- ldata->echo_commit == ldata->echo_tail)
+ ldata->echo_mark == ldata->echo_tail)
return;

mutex_lock(&ldata->output_lock);
+ ldata->echo_commit = ldata->echo_mark;
echoed = __process_echoes(tty);
mutex_unlock(&ldata->output_lock);

@@ -822,6 +826,7 @@ static void process_echoes(struct tty_st
tty->ops->flush_chars(tty);
}

+/* NB: echo_mark and echo_head should be equivalent here */
static void flush_echoes(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;


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