[03/25] tty: serial: apbuart: drop uart_port->lock before calling tty_flip_buffer_push()

Message ID 5eb096b77ce72ef4bc0c2ddc07b4518bca4b88c9.1376651114.git.viresh.kumar@linaro.org
State New
Headers show

Commit Message

Viresh Kumar Aug. 16, 2013, 11:43 a.m.
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/apbuart.c | 2 ++
 1 file changed, 2 insertions(+)

Patch

diff --git a/drivers/tty/serial/apbuart.c b/drivers/tty/serial/apbuart.c
index 6331464d..de11ab8 100644
--- a/drivers/tty/serial/apbuart.c
+++ b/drivers/tty/serial/apbuart.c
@@ -125,7 +125,9 @@  static void apbuart_rx_chars(struct uart_port *port)
 		status = UART_GET_STATUS(port);
 	}
 
+	spin_unlock(&port->lock);
 	tty_flip_buffer_push(&port->state->port);
+	spin_lock(&port->lock);
 }
 
 static void apbuart_tx_chars(struct uart_port *port)