--- x/include/linux/comedi/comedidev.h
+++ y/include/linux/comedi/comedidev.h
@@ -364,6 +364,7 @@ struct comedi_async {
 	struct comedi_cmd cmd;
 	wait_queue_head_t wait_head;
 	unsigned int cb_mask;
+	struct rcu_head rcu;
 	int (*inttrig)(struct comedi_device *dev, struct comedi_subdevice *s,
 		       unsigned int x);
 };
--- l/drivers/comedi/drivers.c
+++ y/drivers/comedi/drivers.c
@@ -168,7 +168,7 @@ static void comedi_device_detach_cleanup
 			comedi_free_subdevice_minor(s);
 			if (s->async) {
 				comedi_buf_alloc(dev, s, 0);
-				kfree(s->async);
+				kfree_rcu(s->async, rcu);
 			}
 			kfree(s->readback);
 		}