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: Stephen Warren <swarren@xxxxxxxxxxxxx>
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
drivers/tty/serial/serial-tegra.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index ee7c812..82846cf 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -571,7 +571,9 @@ static void tegra_uart_rx_dma_complete(void *args)
tegra_uart_handle_rx_pio(tup, port);
if (tty) {
+ spin_unlock_irqrestore(&u->lock, flags);
tty_flip_buffer_push(port);
+ spin_lock_irqsave(&u->lock, flags);
tty_kref_put(tty);
}
tegra_uart_start_rx_dma(tup);
@@ -583,11 +585,13 @@ static void tegra_uart_rx_dma_complete(void *args)
spin_unlock_irqrestore(&u->lock, flags);
}
-static void tegra_uart_handle_rx_dma(struct tegra_uart_port *tup)
+static void tegra_uart_handle_rx_dma(struct tegra_uart_port *tup,
+ unsigned long *flags)
{
struct dma_tx_state state;
struct tty_struct *tty = tty_port_tty_get(&tup->uport.state->port);
struct tty_port *port = &tup->uport.state->port;
+ struct uart_port *u = &tup->uport;
int count;
/* Deactivate flow control to stop sender */
@@ -604,7 +608,9 @@ static void tegra_uart_handle_rx_dma(struct tegra_uart_port *tup)
tegra_uart_handle_rx_pio(tup, port);
if (tty) {
+ spin_unlock_irqrestore(&u->lock, *flags);
tty_flip_buffer_push(port);
+ spin_lock_irqsave(&u->lock, *flags);
tty_kref_put(tty);
}
tegra_uart_start_rx_dma(tup);
@@ -671,7 +677,7 @@ static irqreturn_t tegra_uart_isr(int irq, void *data)
iir = tegra_uart_read(tup, UART_IIR);
if (iir & UART_IIR_NO_INT) {
if (is_rx_int) {
- tegra_uart_handle_rx_dma(tup);
+ tegra_uart_handle_rx_dma(tup, &flags);
if (tup->rx_in_progress) {
ier = tup->ier_shadow;
ier |= (UART_IER_RLSI | UART_IER_RTOIE |
--
1.7.12.rc2.18.g61b472e
--
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