diff mbox

[23/25] tty: serial: tegra: drop uart_port->lock before calling tty_flip_buffer_push()

Message ID d82f1bd4b8e5a19e6059be348f2a3377b3589208.1376651114.git.viresh.kumar@linaro.org
State New
Headers show

Commit Message

Viresh Kumar Aug. 16, 2013, 11:43 a.m. UTC 
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@linutronix.de>
Date:   Tue May 29 21:53:50 2007 +0100

    [ARM] 4417/1: Serial: Fix AMBA drivers locking

Cc: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/tty/serial/serial-tegra.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
diff mbox

Patch

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 |