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[05/25] tty: serial: arc: drop uart_port->lock before calling tty_flip_buffer_push()

Message ID 7af55e73a82958b94e65c8bd275aaa7eb7b88068.1376651114.git.viresh.kumar@linaro.org
State New
Headers show

Commit Message

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

diff --git a/drivers/tty/serial/arc_uart.c b/drivers/tty/serial/arc_uart.c
index 22f280a..8cf6b30 100644
--- a/drivers/tty/serial/arc_uart.c
+++ b/drivers/tty/serial/arc_uart.c
@@ -248,7 +248,9 @@  static void arc_serial_rx_chars(struct arc_uart_port *uart)
 		uart_insert_char(&uart->port, status, RXOERR, ch, flg);
 
 done:
+		spin_unlock(&uart->port.lock);
 		tty_flip_buffer_push(&uart->port.state->port);
+		spin_lock(&uart->port.lock);
 	}
 }