Author: Julia Lawall <julia@diku.dk> dma_channel_np has been accessed at this point, so decrease its reference count before leaving the function. A simplified version of the semantic match that finds this problem is as follows: (http://coccinelle.lip6.fr/) // @@ identifier x; expression E1!=0,E2,E3,E4; statement S; iterator I; @@ ( if (…) { … when != of_node_put(x) when …