From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935915Ab0COJJU (ORCPT ); Mon, 15 Mar 2010 05:09:20 -0400 Received: from www.tglx.de ([62.245.132.106]:56894 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759885Ab0COJJT (ORCPT ); Mon, 15 Mar 2010 05:09:19 -0400 To: Sascha Hauer Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH] serial: fix possible imx deadlock From: John Ogness Date: Mon, 15 Mar 2010 10:08:58 +0100 Message-ID: <80k4tehryt.fsf@merkur.tec.linutronix.de> User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This patch fixes a possible deadlock situation with the port and timer locks. The calling paths for the deadlock situation are: 1. imx_set_termios() -> LOCK(port.lock) -> del_timer_sync() -> LOCK(timer.base.lock) 2. run_timer_softirq() -> LOCK(timer.base.lock) -> imx_timeout() -> LOCK(port.lock) This patch is against 2.6.34-rc1. Signed-off-by: John Ogness --- drivers/serial/imx.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff -Naurp a/drivers/serial/imx.c b/drivers/serial/imx.c --- a/drivers/serial/imx.c 2010-03-08 19:45:44.000000000 +0100 +++ b/drivers/serial/imx.c 2010-03-15 09:52:39.855261060 +0100 @@ -836,6 +836,12 @@ imx_set_termios(struct uart_port *port, baud = uart_get_baud_rate(port, termios, old, 50, port->uartclk / 16); quot = uart_get_divisor(port, baud); + /* + * Stop our timer. This is done with the port unlocked + * to avoid possible deadlock against the timer function. + */ + del_timer_sync(&sport->timer); + spin_lock_irqsave(&sport->port.lock, flags); sport->port.read_status_mask = 0; @@ -860,8 +866,6 @@ imx_set_termios(struct uart_port *port, sport->port.ignore_status_mask |= URXD_OVRRUN; } - del_timer_sync(&sport->timer); - /* * Update the per-port timeout. */