diff --git a/drivers/comedi/comedi_fops.c b/drivers/comedi/comedi_fops.c
index 3383a7ce27ff..ea96bc4b818e 100644
--- a/drivers/comedi/comedi_fops.c
+++ b/drivers/comedi/comedi_fops.c
@@ -785,21 +785,31 @@ void comedi_device_cancel_all(struct comedi_device *dev)
 static int is_device_busy(struct comedi_device *dev)
 {
 	struct comedi_subdevice *s;
-	int i;
+	int i, is_busy = 0;
 
 	lockdep_assert_held(&dev->mutex);
 	if (!dev->attached)
 		return 0;
 
+	/* prevent new polls */
+	down_write(&dev->attach_lock);
+
 	for (i = 0; i < dev->n_subdevices; i++) {
 		s = &dev->subdevices[i];
-		if (s->busy)
-			return 1;
-		if (s->async && comedi_buf_is_mmapped(s))
-			return 1;
+		if (s->busy) {
+			is_busy = 1;
+			break;
+		}
+		if (!s->async)
+			continue;
+		if (comedi_buf_is_mmapped(s) ||
+		    waitqueue_active(&s->async->wait_head)) {
+			is_busy = 1;
+			break;
+		}
 	}
-
-	return 0;
+	up_write(&dev->attach_lock);
+	return is_busy;
 }
 
 /*