From 019ebdf9f26fd2e43b9e1af576835183e95dc82e Mon Sep 17 00:00:00 2001 From: Peter Hurley Date: Sat, 15 Jun 2013 10:04:25 -0400 Subject: [PATCH] n_tty: Eliminate echo_commit memory barrier Use output_lock mutex as a memory barrier when storing echo_commit. Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_tty.c | 31 ++++++++++++++++++++----------- 1 file changed, 20 insertions(+), 11 deletions(-) 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 @@ break_out: * 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 @@ static void process_echoes(struct tty_struct *tty) } ldata->echo_tail = tail; +} + +static void commit_echoes(struct tty_struct *tty) +{ + struct n_tty_data *ldata = tty->disc_data; + mutex_lock(&ldata->output_lock); + ldata->echo_commit = ldata->echo_head; + __process_echoes(tty); mutex_unlock(&ldata->output_lock); if (tty->ops->flush_chars) tty->ops->flush_chars(tty); } -static void commit_echoes(struct tty_struct *tty) +static void process_echoes(struct tty_struct *tty) { struct n_tty_data *ldata = tty->disc_data; - smp_mb(); - ldata->echo_commit = ldata->echo_head; - process_echoes(tty); + 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); } /** -- 2.7.4