From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755541AbaIBVm7 (ORCPT ); Tue, 2 Sep 2014 17:42:59 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:41859 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755311AbaIBVkG (ORCPT ); Tue, 2 Sep 2014 17:40:06 -0400 From: Peter Hurley To: Greg Kroah-Hartman Cc: Jiri Slaby , One Thousand Gnomes , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Hurley Subject: [PATCH 05/26] serial: core: Remove unsafe x_char optimization Date: Tue, 2 Sep 2014 17:39:14 -0400 Message-Id: <1409693975-1028-6-git-send-email-peter@hurleysoftware.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1409693975-1028-1-git-send-email-peter@hurleysoftware.com> References: <1409693975-1028-1-git-send-email-peter@hurleysoftware.com> X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org uart_unthrottle() attempts to avoid sending START and the previous x_char if the previous x_char has not yet been sent. However, this optimization could leave the sender in a throttled state; for example, if the sender is throttled and this unthrottle coincides with a manual tcflow(TCION) from user-space, then neither START would be sent. Signed-off-by: Peter Hurley --- drivers/tty/serial/serial_core.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index a68bff0..11c8fe6 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -643,12 +643,8 @@ static void uart_unthrottle(struct tty_struct *tty) mask &= ~port->flags; } - if (mask & UPF_SOFT_FLOW) { - if (port->x_char) - port->x_char = 0; - else - uart_send_xchar(tty, START_CHAR(tty)); - } + if (mask & UPF_SOFT_FLOW) + uart_send_xchar(tty, START_CHAR(tty)); if (mask & UPF_HARD_FLOW) uart_set_mctrl(port, TIOCM_RTS); -- 2.1.0