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/mpsc.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/mpsc.c b/drivers/tty/serial/mpsc.c
index bc24f49..556ff04 100644
--- a/drivers/tty/serial/mpsc.c
+++ b/drivers/tty/serial/mpsc.c
@@ -934,7 +934,7 @@ static int serial_polled;
******************************************************************************
*/
-static int mpsc_rx_intr(struct mpsc_port_info *pi)
+static int mpsc_rx_intr(struct mpsc_port_info *pi, unsigned long *flags)
{
struct mpsc_rx_desc *rxre;
struct tty_port *port = &pi->port.state->port;
@@ -969,8 +969,11 @@ static int mpsc_rx_intr(struct mpsc_port_info *pi)
#endif
/* Following use of tty struct directly is deprecated */
if (tty_buffer_request_room(port, bytes_in) < bytes_in) {
- if (port->low_latency)
+ if (port->low_latency) {
+ spin_unlock_irqrestore(&pi->port.lock, *flags);
tty_flip_buffer_push(port);
+ spin_lock_irqsave(&pi->port.lock, *flags);
+ }
/*
* If this failed then we will throw away the bytes
* but must do so to clear interrupts.
@@ -1080,7 +1083,9 @@ next_frame:
if ((readl(pi->sdma_base + SDMA_SDCM) & SDMA_SDCM_ERD) == 0)
mpsc_start_rx(pi);
+ spin_unlock_irqrestore(&pi->port.lock, *flags);
tty_flip_buffer_push(port);
+ spin_lock_irqsave(&pi->port.lock, *flags);
return rc;
}
@@ -1222,7 +1227,7 @@ static irqreturn_t mpsc_sdma_intr(int irq, void *dev_id)
spin_lock_irqsave(&pi->port.lock, iflags);
mpsc_sdma_intr_ack(pi);
- if (mpsc_rx_intr(pi))
+ if (mpsc_rx_intr(pi, &iflags))
rc = IRQ_HANDLED;
if (mpsc_tx_intr(pi))
rc = IRQ_HANDLED;
--
1.7.12.rc2.18.g61b472e
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