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[16/25] tty: serial: msm: drop uart_port->lock before calling tty_flip_buffer_push()

Message ID a6e0375d43f960df1f98e4055977eac044c16b06.1376651114.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

Cc: David Brown <davidb@codeaurora.org> (maintainer:ARM/QUALCOMM MSM...)
Cc: Daniel Walker <dwalker@fifo99.com> (maintainer:ARM/QUALCOMM MSM...)
Cc: Bryan Huntsman <bryanh@codeaurora.org> (maintainer:ARM/QUALCOMM MSM...)
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/tty/serial/msm_serial.c | 5 +++++
 1 file changed, 5 insertions(+)
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Patch

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 2c6cfb3..daa2837 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -137,7 +137,10 @@  static void handle_rx_dm(struct uart_port *port, unsigned int misr)
 		count -= 4;
 	}
 
+	spin_unlock(&port->lock);
 	tty_flip_buffer_push(tport);
+	spin_lock(&port->lock);
+
 	if (misr & (UART_IMR_RXSTALE))
 		msm_write(port, UART_CR_CMD_RESET_STALE_INT, UART_CR);
 	msm_write(port, 0xFFFFFF, UARTDM_DMRX);
@@ -189,7 +192,9 @@  static void handle_rx(struct uart_port *port)
 			tty_insert_flip_char(tport, c, flag);
 	}
 
+	spin_unlock(&port->lock);
 	tty_flip_buffer_push(tport);
+	spin_lock(&port->lock);
 }
 
 static void reset_dm_count(struct uart_port *port)