CHN_INSERT_HEAD
CHN_INSERT_HEAD(d, c, channels.pcm.busy);
CHN_INSERT_HEAD(x, y, z); \
CHN_INSERT_HEAD(x, y, z); \
CHN_INSERT_HEAD(d, rdch, channels.pcm.opened);
CHN_INSERT_HEAD(d, wrch, channels.pcm.opened);
CHN_INSERT_HEAD(p, c, children.busy);