IS_EMPTY
ASSERT(b->tqbucket_nfree != 0 || IS_EMPTY(b->tqbucket_freelist));
ASSERT(b->tqbucket_nfree == 0 || !IS_EMPTY(b->tqbucket_freelist));
IMPLY(idleb->tqbucket_nfree == 0, IS_EMPTY(idleb->tqbucket_freelist));
IMPLY(idleb->tqbucket_nfree != 0, !IS_EMPTY(idleb->tqbucket_freelist));
ASSERT(!IS_EMPTY(bucket->tqbucket_backlog));
ASSERT(!IS_EMPTY(idle_bucket->tqbucket_freelist));