diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c
index 5d3999e..b37d65f 100644
--- a/drivers/usb/serial/option.c
+++ b/drivers/usb/serial/option.c
@@ -38,6 +38,7 @@
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
 #include <linux/module.h>
+#include <linux/bitops.h>
 #include <linux/usb.h>
 #include <linux/usb/serial.h>
 
@@ -240,6 +241,7 @@
 	/* Output endpoints and buffer for this port */
 	struct urb *out_urbs[N_OUT_URB];
 	char out_buffer[N_OUT_URB][OUT_BUFLEN];
+	unsigned long out_busy;		/* Bit vector of URBs in use */
 
 	/* Settings for the port */
 	int rts_state;	/* Handshaking pins (outputs) */
@@ -370,7 +372,7 @@
 			todo = OUT_BUFLEN;
 
 		this_urb = portdata->out_urbs[i];
-		if (this_urb->status == -EINPROGRESS) {
+		if (test_and_set_bit(i, &portdata->out_busy)) {
 			if (time_before(jiffies,
 					portdata->tx_start_time[i] + 10 * HZ))
 				continue;
@@ -394,6 +396,7 @@
 			dbg("usb_submit_urb %p (write bulk) failed "
 				"(%d, has %d)", this_urb,
 				err, this_urb->status);
+			clear_bit(i, &portdata->out_busy);
 			continue;
 		}
 		portdata->tx_start_time[i] = jiffies;
@@ -446,12 +449,23 @@
 static void option_outdat_callback(struct urb *urb)
 {
 	struct usb_serial_port *port;
+	struct option_port_private *portdata;
+	int i;
 
 	dbg("%s", __FUNCTION__);
 
 	port = (struct usb_serial_port *) urb->context;
 
 	usb_serial_port_softint(port);
+
+	portdata = usb_get_serial_port_data(port);
+	for (i = 0; i < N_OUT_URB; ++i) {
+		if (portdata->out_urbs[i] == urb) {
+			smp_mb__before_clear_bit();
+			clear_bit(i, &portdata->out_busy);
+			break;
+		}
+	}
 }
 
 static void option_instat_callback(struct urb *urb)
@@ -518,7 +532,7 @@
 
 	for (i=0; i < N_OUT_URB; i++) {
 		this_urb = portdata->out_urbs[i];
-		if (this_urb && this_urb->status != -EINPROGRESS)
+		if (this_urb && !test_bit(i, &portdata->out_busy))
 			data_len += OUT_BUFLEN;
 	}
 
@@ -537,7 +551,7 @@
 
 	for (i=0; i < N_OUT_URB; i++) {
 		this_urb = portdata->out_urbs[i];
-		if (this_urb && this_urb->status == -EINPROGRESS)
+		if (this_urb && test_bit(i, &portdata->out_busy))
 			data_len += this_urb->transfer_buffer_length;
 	}
 	dbg("%s: %d", __FUNCTION__, data_len);