From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932456Ab1LOKAo (ORCPT ); Thu, 15 Dec 2011 05:00:44 -0500 Received: from newsmtp5.atmel.com ([204.2.163.5]:12260 "EHLO sjogate2.atmel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752667Ab1LOKAm (ORCPT ); Thu, 15 Dec 2011 05:00:42 -0500 Message-ID: <4EE9C532.5050607@atmel.com> Date: Thu, 15 Dec 2011 11:00:18 +0100 From: Nicolas Ferre Organization: atmel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111124 Thunderbird/8.0 MIME-Version: 1.0 To: Claudio Scordino CC: Alan Cox , Linux Kernel , "linux-serial@vger.kernel.org" , Dave Bender Subject: Re: [PATCH] atmel_serial: fix spinlock lockup in RS485 code References: <4EE9B42F.50004@evidence.eu.com> In-Reply-To: <4EE9B42F.50004@evidence.eu.com> X-Enigmail-Version: 1.4a1pre Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/15/2011 09:47 AM, Claudio Scordino : > 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 Acked-by: Nicolas Ferre Claudio, can you please send the patch to Alan with my "Acked-by" and an addition to Linux stable just after the signature lines: Cc: stable Thanks, best regards, > --- > 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); > > } > -- Nicolas Ferre