From mboxrd@z Thu Jan 1 00:00:00 1970 From: Claudio Scordino Subject: Re: [PATCH] atmel_serial: fix spinlock lockup in RS485 code Date: Thu, 15 Dec 2011 12:04:42 +0100 Message-ID: <4EE9D44A.6010300@evidence.eu.com> References: <4EE9B42F.50004@evidence.eu.com> <4EE9C532.5050607@atmel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4EE9C532.5050607@atmel.com> Sender: linux-kernel-owner@vger.kernel.org To: Alan Cox Cc: Nicolas Ferre , Linux Kernel , "linux-serial@vger.kernel.org" , Dave Bender List-Id: linux-serial@vger.kernel.org Il 15/12/2011 11:00, Nicolas Ferre ha scritto: > 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 Dear Alan, here is the patch with all the acked-bys. Many thanks, 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 Acked-by: Alan Cox Cc: stable --- 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