When INVARIANTS is not set the 'last' variable is not used, which can generate compiler warnings. If this invariant is ever violated it'd result in a KASSERT failure in refcount_release(), so this one is not strictly required.
When INVARIANTS is not set the 'last' variable is not used, which can generate compiler warnings. If this invariant is ever violated it'd result in a KASSERT failure in refcount_release(), so this one is not strictly required.