Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754695Ab3FOOFh (ORCPT ); Sat, 15 Jun 2013 10:05:37 -0400 Received: from mailout01.c08.mtsvc.net ([205.186.168.189]:40206 "EHLO mailout01.c08.mtsvc.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754452Ab3FOOFD (ORCPT ); Sat, 15 Jun 2013 10:05:03 -0400 From: Peter Hurley To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Jiri Slaby , Peter Hurley Subject: [PATCH v2 5/9] n_tty: Eliminate echo_commit memory barrier Date: Sat, 15 Jun 2013 10:04:25 -0400 Message-Id: <1371305069-5366-6-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1371305069-5366-1-git-send-email-peter@hurleysoftware.com> References: <1371303376-5028-1-git-send-email-peter@hurleysoftware.com> <1371305069-5366-1-git-send-email-peter@hurleysoftware.com> X-Authenticated-User: 125194 peter@hurleysoftware.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2180 Lines: 82 Use output_lock mutex as a memory barrier when storing echo_commit. Signed-off-by: Peter Hurley --- 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 d22c14c..c595264 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -637,21 +637,16 @@ 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; @@ -771,20 +766,34 @@ 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); } /** -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/