Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752295AbbDZNrX (ORCPT ); Sun, 26 Apr 2015 09:47:23 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:40514 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751202AbbDZNrT (ORCPT ); Sun, 26 Apr 2015 09:47:19 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tim Kryger , Zhang Zhen , Peter Hurley Subject: [PATCH 3.10 14/31] serial: 8250_dw: Fix deadlock in LCR workaround Date: Sun, 26 Apr 2015 15:46:34 +0200 Message-Id: <20150426134209.944689314@linuxfoundation.org> X-Mailer: git-send-email 2.3.6 In-Reply-To: <20150426134209.255099785@linuxfoundation.org> References: <20150426134209.255099785@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2119 Lines: 68 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Hurley commit 7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11 upstream. Trying to write console output from within the serial console driver while the port->lock is held causes recursive deadlock: CPU 0 spin_lock_irqsave(&port->lock) printk() console_unlock() call_console_drivers() serial8250_console_write() spin_lock_irqsave(&port->lock) ** DEADLOCK ** The 8250_dw i/o accessors try to write a console error message if the LCR workaround was unsuccessful. When the port->lock is already held (eg., when called from serial8250_set_termios()), this deadlocks. Make the error message a FIXME until a general solution is devised. Cc: Tim Kryger Reported-by: Zhang Zhen Signed-off-by: Peter Hurley Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_dw.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -98,7 +98,10 @@ static void dw8250_serial_out(struct uar dw8250_force_idle(p); writeb(value, p->membase + (UART_LCR << p->regshift)); } - dev_err(p->dev, "Couldn't set LCR to %d\n", value); + /* + * FIXME: this deadlocks if port->lock is already held + * dev_err(p->dev, "Couldn't set LCR to %d\n", value); + */ } } @@ -128,7 +131,10 @@ static void dw8250_serial_out32(struct u dw8250_force_idle(p); writel(value, p->membase + (UART_LCR << p->regshift)); } - dev_err(p->dev, "Couldn't set LCR to %d\n", value); + /* + * FIXME: this deadlocks if port->lock is already held + * dev_err(p->dev, "Couldn't set LCR to %d\n", value); + */ } } -- 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/