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
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
drivers/tty/serial/m32r_sio.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/tty/serial/m32r_sio.c b/drivers/tty/serial/m32r_sio.c
index bb1afa0..9cd9b4e 100644
--- a/drivers/tty/serial/m32r_sio.c
+++ b/drivers/tty/serial/m32r_sio.c
@@ -368,7 +368,10 @@ static void receive_chars(struct uart_sio_port *up, int *status)
ignore_char:
*status = serial_in(up, UART_LSR);
} while ((*status & UART_LSR_DR) && (max_count-- > 0));
+
+ spin_unlock(&up->port.lock);
tty_flip_buffer_push(port);
+ spin_lock(&up->port.lock);
}
static void transmit_chars(struct uart_sio_port *up)
--
1.7.12.rc2.18.g61b472e
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