From patchwork Thu Jul 30 22:54:21 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Ogness X-Patchwork-Id: 6907361 Return-Path: X-Original-To: patchwork-linux-omap@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 52974C05AC for ; Thu, 30 Jul 2015 22:54:44 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 873FE205F0 for ; Thu, 30 Jul 2015 22:54:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D0D1920624 for ; Thu, 30 Jul 2015 22:54:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752304AbbG3Wya (ORCPT ); Thu, 30 Jul 2015 18:54:30 -0400 Received: from www.linutronix.de ([62.245.132.108]:48974 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750905AbbG3Wy2 (ORCPT ); Thu, 30 Jul 2015 18:54:28 -0400 Received: from localhost ([127.0.0.1] helo=vostro.local) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1ZKwiW-00005F-Fb; Fri, 31 Jul 2015 00:54:24 +0200 From: John Ogness To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman Cc: Tony Lindgren Cc: Peter Hurley Cc: Sebastian Andrzej Siewior Cc: linux-omap@vger.kernel.org Cc: nsekhar@ti.com Cc: tony@atomide.com Cc: nm@ti.com Cc: linux-serial@vger.kernel.org Subject: [PATCH 1/3] serial: 8250: unlock port for uart_write_wakeup() Date: Fri, 31 Jul 2015 00:54:21 +0200 Message-ID: <87h9ol2r4y.fsf@linutronix.de> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.4 (gnu/linux) MIME-Version: 1.0 X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1, SHORTCIRCUIT=-0.0001 Sender: linux-omap-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org X-Spam-Status: No, score=-8.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP uart_write_wakeup() should be called without holding the port lock. Otherwise a possible recursive spinlock issue can occur, such as the following callchain: 8250_core.c:serial8250_tx_chars() - called with port locked serial_core.c:uart_write_wakeup() tty_io.c:tty_wakeup() st_core.c:st_tty_wakeup() st_core.c:st_tx_wakeup() st_core.c:st_int_write() serial_core.c:uart_write() - locks port Signed-off-by: John Ogness --- drivers/tty/serial/8250/8250_core.c | 6 +++++- drivers/tty/serial/8250/8250_omap.c | 6 +++++- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 37fff12..5ac2425 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -1559,8 +1559,12 @@ void serial8250_tx_chars(struct uart_8250_port *up) } } while (--count > 0); - if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) + if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) { + /* do not hold lock for call to uart_write_wakeup() */ + spin_unlock(&port->lock); uart_write_wakeup(port); + spin_lock(&port->lock); + } DEBUG_INTR("THRE..."); diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index d75a66c..5b39892 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -861,8 +861,12 @@ static void omap_8250_dma_tx_complete(void *param) omap8250_restore_regs(p); } - if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) + if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) { + /* do not hold lock for call to uart_write_wakeup() */ + spin_unlock(&p->port.lock); uart_write_wakeup(&p->port); + spin_lock(&p->port.lock); + } if (!uart_circ_empty(xmit) && !uart_tx_stopped(&p->port)) { int ret;