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/nwpserial.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/tty/serial/nwpserial.c b/drivers/tty/serial/nwpserial.c
index 549c70a..693bc6c 100644
--- a/drivers/tty/serial/nwpserial.c
+++ b/drivers/tty/serial/nwpserial.c
@@ -149,7 +149,10 @@ static irqreturn_t nwpserial_interrupt(int irq, void *dev_id)
tty_insert_flip_char(port, ch, TTY_NORMAL);
} while (dcr_read(up->dcr_host, UART_LSR) & UART_LSR_DR);
+ spin_unlock(&up->port.lock);
tty_flip_buffer_push(port);
+ spin_lock(&up->port.lock);
+
ret = IRQ_HANDLED;
/* clear interrupt */
--
1.7.12.rc2.18.g61b472e
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