diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 7bc5329fa3ed..21417b4c5154 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -331,7 +331,6 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf)
 
 		spin_lock_irqsave(&acm->read_lock, flags);
 		acm->ctrlin = newctrl;
-		acm->oldcount = acm->iocount;
 
 		if (difference & USB_CDC_SERIAL_STATE_DSR)
 			acm->iocount.dsr++;
@@ -1027,11 +1026,16 @@ static int wait_serial_change(struct acm *acm, unsigned long arg)
 	DECLARE_WAITQUEUE(wait, current);
 	struct async_icount old, new;
 
-	do {
+	spin_lock_irq(&acm->read_lock);
+	old = acm->iocount;
+	spin_unlock_irq(&acm->read_lock);
+
+	add_wait_queue(&acm->wioctl, &wait);
+	for (;;) {
+		set_current_state(TASK_INTERRUPTIBLE);
+
 		spin_lock_irq(&acm->read_lock);
-		old = acm->oldcount;
 		new = acm->iocount;
-		acm->oldcount = new;
 		spin_unlock_irq(&acm->read_lock);
 
 		if ((arg & TIOCM_DSR) &&
@@ -1044,22 +1048,20 @@ static int wait_serial_change(struct acm *acm, unsigned long arg)
 			old.rng != new.rng)
 			break;
 
-		add_wait_queue(&acm->wioctl, &wait);
-		set_current_state(TASK_INTERRUPTIBLE);
-		schedule();
-		remove_wait_queue(&acm->wioctl, &wait);
 		if (acm->disconnected) {
-			if (arg & TIOCM_CD)
-				break;
-			else
-				rv = -ENODEV;
-		} else {
-			if (signal_pending(current))
-				rv = -ERESTARTSYS;
+			rv = -ENODEV;
+			break;
 		}
-	} while (!rv);
 
-	
+		schedule();
+
+		if (signal_pending(current)) {
+			rv = -ERESTARTSYS;
+			break;
+		}
+	}
+	__set_current_state(TASK_RUNNING);
+	remove_wait_queue(&acm->wioctl, &wait);
 
 	return rv;
 }
diff --git a/drivers/usb/class/cdc-acm.h b/drivers/usb/class/cdc-acm.h
index 01f448a783c0..d245e60eb9f5 100644
--- a/drivers/usb/class/cdc-acm.h
+++ b/drivers/usb/class/cdc-acm.h
@@ -90,7 +90,6 @@ struct acm {
 	unsigned int ctrlin;				/* input control lines (DCD, DSR, RI, break, overruns) */
 	unsigned int ctrlout;				/* output control lines (DTR, RTS) */
 	struct async_icount iocount;			/* counters for control line changes */
-	struct async_icount oldcount;			/* for comparison of counter */
 	wait_queue_head_t wioctl;			/* for ioctl */
 	unsigned int writesize;				/* max packet size for the output bulk endpoint */
 	unsigned int readsize,ctrlsize;			/* buffer sizes for freeing */