diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index c8cb0b398cb19..6db8844ef3ecd 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -195,6 +195,7 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
 {
 	struct uart_port *uport = uart_port_check(state);
 	unsigned long page;
+	unsigned long flags = 0;
 	int retval = 0;
 
 	if (uport->type == PORT_UNKNOWN)
@@ -209,15 +210,18 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
 	 * Initialise and allocate the transmit and temporary
 	 * buffer.
 	 */
-	if (!state->xmit.buf) {
-		/* This is protected by the per port mutex */
-		page = get_zeroed_page(GFP_KERNEL);
-		if (!page)
-			return -ENOMEM;
+	page = get_zeroed_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
 
+	uart_port_lock(state, flags);
+	if (!state->xmit.buf) {
 		state->xmit.buf = (unsigned char *) page;
 		uart_circ_clear(&state->xmit);
+	} else {
+		free_page(page);
 	}
+	uart_port_unlock(uport, flags);
 
 	retval = uport->ops->startup(uport);
 	if (retval == 0) {
@@ -276,6 +280,7 @@ static void uart_shutdown(struct tty_struct *tty, struct uart_state *state)
 {
 	struct uart_port *uport = uart_port_check(state);
 	struct tty_port *port = &state->port;
+	unsigned long flags = 0;
 
 	/*
 	 * Set the TTY IO error marker
@@ -308,10 +313,12 @@ static void uart_shutdown(struct tty_struct *tty, struct uart_state *state)
 	/*
 	 * Free the transmit buffer page.
 	 */
+	uart_port_lock(state, flags);
 	if (state->xmit.buf) {
 		free_page((unsigned long)state->xmit.buf);
 		state->xmit.buf = NULL;
 	}
+	uart_port_unlock(uport, flags);
 }
 
 /**