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@xxxxxxxxxxxxx>
Date: Tue May 29 21:53:50 2007 +0100
[ARM] 4417/1: Serial: Fix AMBA drivers locking
Cc: David Brown <davidb@xxxxxxxxxxxxxx> (maintainer:ARM/QUALCOMM MSM...)
Cc: Daniel Walker <dwalker@xxxxxxxxxx> (maintainer:ARM/QUALCOMM MSM...)
Cc: Bryan Huntsman <bryanh@xxxxxxxxxxxxxx> (maintainer:ARM/QUALCOMM MSM...)
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
drivers/tty/serial/msm_serial.c | 5 +++++
1 file changed, 5 insertions(+)
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)
--
1.7.12.rc2.18.g61b472e
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