quoted

@@ -1184,8 +1183,7 @@ EXPORT_SYMBOL_GPL(i2c_new_dummy);
 
 static void i2c_adapter_dev_release(struct device *dev)
 {
-	struct i2c_adapter *adap = to_i2c_adapter(dev);
-	complete(&adap->dev_released);
+	/* empty, but the driver core insists we need a release function */

Yeah, it does, but I hate to see this in "real" code as something is
probably wrong with it if it happens.

Please move the rest of 'i2c_del_adapter' into the release function
(what was after the wait_for_completion() call), and then all should be
fine.

I was about to do this as a follow-up patch. But Russell's and
Lars-Peter's responses made this obsolete already.