The -rt patch triggers a lockdep warning for serial drivers if tty_flip_buffer_push() is called with uart_port->lock locked. This never shows up on UP kernels.
Release the port lock before calling tty_flip_buffer_push() and reacquire it after the call.
Similar stuff was already done for few other drivers in the past, like:
commit 2389b272168ceec056ca1d8a870a97fa9c26e11a Author: Thomas Gleixner tglx@linutronix.de Date: Tue May 29 21:53:50 2007 +0100
[ARM] 4417/1: Serial: Fix AMBA drivers locking
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- drivers/tty/serial/efm32-uart.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/efm32-uart.c b/drivers/tty/serial/efm32-uart.c index 7d199c8..b4cef79 100644 --- a/drivers/tty/serial/efm32-uart.c +++ b/drivers/tty/serial/efm32-uart.c @@ -268,10 +268,10 @@ static irqreturn_t efm32_uart_rxirq(int irq, void *data) handled = IRQ_HANDLED; }
- tty_flip_buffer_push(tport); - spin_unlock(&port->lock);
+ tty_flip_buffer_push(tport); + return handled; }