C_FREE
if ((xfer->c_flags & (C_FREE|C_WAITTIMO)) == C_FREE) {
xfer->c_flags |= C_FREE;
if (xfer->c_flags & C_FREE) {
xfer->c_flags &= ~C_FREE;
KASSERT((xfer->c_flags & (C_WAITACT|C_FREE)) == 0);