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/mcf.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/tty/serial/mcf.c b/drivers/tty/serial/mcf.c
index 65be0c0..62c8fdf 100644
--- a/drivers/tty/serial/mcf.c
+++ b/drivers/tty/serial/mcf.c
@@ -324,7 +324,9 @@ static void mcf_rx_chars(struct mcf_uart *pp)
uart_insert_char(port, status, MCFUART_USR_RXOVERRUN, ch, flag);
}
+ spin_unlock(&port->lock);
tty_flip_buffer_push(&port->state->port);
+ spin_lock(&port->lock);
}
/****************************************************************************/
--
1.7.12.rc2.18.g61b472e
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