[01/25] tty: serial: altera_jtag: drop uart_port->lock before calling tty_flip_buffer_push()

Message ID b57aa015f0c91ba2ab6e2f1b18f46df4e71cdad7.1376651114.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

Cc: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/tty/serial/altera_jtaguart.c | 2 ++
 1 file changed, 2 insertions(+)

Patch

diff --git a/drivers/tty/serial/altera_jtaguart.c b/drivers/tty/serial/altera_jtaguart.c
index c6bdb94..46c25ff 100644
--- a/drivers/tty/serial/altera_jtaguart.c
+++ b/drivers/tty/serial/altera_jtaguart.c
@@ -139,7 +139,9 @@  static void altera_jtaguart_rx_chars(struct altera_jtaguart *pp)
 		uart_insert_char(port, 0, 0, ch, flag);
 	}
 
+	spin_unlock(&port->lock);
 	tty_flip_buffer_push(&port->state->port);
+	spin_lock(&port->lock);
 }
 
 static void altera_jtaguart_tx_chars(struct altera_jtaguart *pp)