From mboxrd@z Thu Jan 1 00:00:00 1970 From: Claudio Scordino Subject: [PATCH] atmel_serial: fix spinlock lockup in RS485 code Date: Thu, 15 Dec 2011 09:47:43 +0100 Message-ID: <4EE9B42F.50004@evidence.eu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ey0-f174.google.com ([209.85.215.174]:33803 "EHLO mail-ey0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752340Ab1LOIrt (ORCPT ); Thu, 15 Dec 2011 03:47:49 -0500 Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Nicolas Ferre , Alan Cox Cc: Linux Kernel , "linux-serial@vger.kernel.org" , Dave Bender Hi all. We have encountered a spinlock lockup in the RS485 part of the atmel_serial driver. Here is the trace: [ 68.030000] BUG: spinlock lockup on CPU#0, dnp_master/244, c07e82c0 [ 68.040000] [] (unwind_backtrace+0x0/0xf0) from [] (do_raw_spin_lock+0x10c/0x148) [ 68.050000] [] (do_raw_spin_lock+0x10c/0x148) from [] (atmel_tasklet_func+0x10/0x708) [ 68.060000] [] (atmel_tasklet_func+0x10/0x708) from [] (tasklet_action+0x8c/0xf4) [ 68.070000] [] (tasklet_action+0x8c/0xf4) from [] (__do_softirq+0xa4/0x180) [ 68.080000] [] (__do_softirq+0xa4/0x180) from [] (irq_exit+0x58/0xb0) [ 68.090000] [] (irq_exit+0x58/0xb0) from [] (asm_do_IRQ+0x84/0xa4) [ 68.100000] [] (asm_do_IRQ+0x84/0xa4) from [] (__irq_svc+0x4c/0x98) [ 68.110000] Exception stack(0xc341fdc8 to 0xc341fe10) [ 68.110000] fdc0: c07e82c0 00000000 00000200 c4818000 c341fe10 c07e82c0 [ 68.120000] fde0: 00000000 c07e82c0 c38d3318 c341e000 bebcee00 010a0b60 c07e83fc c341fe10 [ 68.130000] fe00: c0151d54 c023d9c0 60000013 ffffffff [ 68.140000] [] (__irq_svc+0x4c/0x98) from [] (_raw_spin_unlock+0x0/0x48) [ 68.140000] [] (_raw_spin_unlock+0x0/0x48) from [<00000000>] ( (null)) The soft lockup occurs later [ 126.750000] BUG: soft lockup - CPU#0 stuck for 61s! [dnp_master:244] [ 126.750000] irq event stamp: 0 [ 126.750000] hardirqs last enabled at (0): [< (null)>] (null) [ 126.750000] hardirqs last disabled at (0): [] copy_process+0x308/0xe78 [ 126.750000] softirqs last enabled at (0): [] copy_process+0x308/0xe78 [ 126.750000] softirqs last disabled at (0): [< (null)>] (null) The following patch (already tested by Dave, who also reported the bug) fixes the problem. Regards, Claudio Subject: atmel_serial: fix spinlock lockup in RS485 code Patch to fix a spinlock lockup in the driver that sometimes happens when the tasklet starts. Signed-off-by: Claudio Scordino Signed-off-by: Dave Bender Tested-by: Dave Bender --- drivers/tty/serial/atmel_serial.c | 5 +++-- 1 files changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index 4c823f3..90c8e3a 100644 --- a/drivers/tty/serial/atmel_serial.c +++ b/drivers/tty/serial/atmel_serial.c @@ -212,8 +212,9 @@ void atmel_config_rs485(struct uart_port *port, struct serial_rs485 *rs485conf) { struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); unsigned int mode; + unsigned long flags; - spin_lock(&port->lock); + spin_lock_irqsave(&port->lock, flags); /* Disable interrupts */ UART_PUT_IDR(port, atmel_port->tx_done_mask); @@ -244,7 +245,7 @@ void atmel_config_rs485(struct uart_port *port, struct serial_rs485 *rs485conf) /* Enable interrupts */ UART_PUT_IER(port, atmel_port->tx_done_mask); - spin_unlock(&port->lock); + spin_unlock_irqrestore(&port->lock, flags); } -- 1.7.1