n_tty: Eliminate echo_commit memory barrier
Use output_lock mutex as a memory barrier when storing echo_commit.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 3b49945..0f76b90 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -638,21 +638,16 @@
* are prioritized. Also, when control characters are echoed with a
* prefixed "^", the pair is treated atomically and thus not separated.
*
- * Locking: output_lock to protect column state and space left
+ * Locking: callers must hold output_lock
*/
-static void process_echoes(struct tty_struct *tty)
+static void __process_echoes(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
int space, nr;
size_t tail;
unsigned char c;
- if (ldata->echo_commit == ldata->echo_tail)
- return;
-
- mutex_lock(&ldata->output_lock);
-
space = tty_write_room(tty);
tail = ldata->echo_tail;
@@ -772,20 +767,34 @@
}
ldata->echo_tail = tail;
-
- mutex_unlock(&ldata->output_lock);
-
- if (tty->ops->flush_chars)
- tty->ops->flush_chars(tty);
}
static void commit_echoes(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
- smp_mb();
+ mutex_lock(&ldata->output_lock);
ldata->echo_commit = ldata->echo_head;
- process_echoes(tty);
+ __process_echoes(tty);
+ mutex_unlock(&ldata->output_lock);
+
+ if (tty->ops->flush_chars)
+ tty->ops->flush_chars(tty);
+}
+
+static void process_echoes(struct tty_struct *tty)
+{
+ struct n_tty_data *ldata = tty->disc_data;
+
+ if (!L_ECHO(tty) || ldata->echo_commit == ldata->echo_tail)
+ return;
+
+ mutex_lock(&ldata->output_lock);
+ __process_echoes(tty);
+ mutex_unlock(&ldata->output_lock);
+
+ if (tty->ops->flush_chars)
+ tty->ops->flush_chars(tty);
}
/**