Messages in this thread Patch in this message | | | Date | Thu, 15 Dec 2011 09:47:43 +0100 | From | Claudio Scordino <> | Subject | [PATCH] atmel_serial: fix spinlock lockup in RS485 code |
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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] [<c002a790>] (unwind_backtrace+0x0/0xf0) from [<c012f8f0>] (do_raw_spin_lock+0x10c/0x148) [ 68.050000] [<c012f8f0>] (do_raw_spin_lock+0x10c/0x148) from [<c015152c>] (atmel_tasklet_func+0x10/0x708) [ 68.060000] [<c015152c>] (atmel_tasklet_func+0x10/0x708) from [<c003bfd4>] (tasklet_action+0x8c/0xf4) [ 68.070000] [<c003bfd4>] (tasklet_action+0x8c/0xf4) from [<c003c630>] (__do_softirq+0xa4/0x180) [ 68.080000] [<c003c630>] (__do_softirq+0xa4/0x180) from [<c003c764>] (irq_exit+0x58/0xb0) [ 68.090000] [<c003c764>] (irq_exit+0x58/0xb0) from [<c0021084>] (asm_do_IRQ+0x84/0xa4) [ 68.100000] [<c0021084>] (asm_do_IRQ+0x84/0xa4) from [<c002622c>] (__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] [<c002622c>] (__irq_svc+0x4c/0x98) from [<c023d9c0>] (_raw_spin_unlock+0x0/0x48) [ 68.140000] [<c023d9c0>] (_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): [<c0035e30>] copy_process+0x308/0xe78 [ 126.750000] softirqs last enabled at (0): [<c0035e30>] 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 <claudio@evidence.eu.com> Signed-off-by: Dave Bender <codehero@gmail.com> Tested-by: Dave Bender <codehero@gmail.com> --- 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
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