NM_FAIL_ON
NM_FAIL_ON(kring->nr_hwcur >= n || kring->rhead >= n ||
NM_FAIL_ON(head < kring->rhead || head > kring->rtail);
NM_FAIL_ON(cur < head || cur > kring->rtail);
NM_FAIL_ON(head > kring->rtail && head < kring->rhead);
NM_FAIL_ON(cur < head || cur > kring->rtail);
NM_FAIL_ON(cur > kring->rtail && cur < head);
NM_FAIL_ON(kring->nr_hwcur >= n || kring->nr_hwtail >= n);
NM_FAIL_ON(head < kring->nr_hwcur || head > kring->nr_hwtail);
NM_FAIL_ON(cur < head || cur > kring->nr_hwtail);
NM_FAIL_ON(head < kring->nr_hwcur && head > kring->nr_hwtail);
NM_FAIL_ON(cur < head || cur > kring->nr_hwtail);
NM_FAIL_ON(cur < head && cur > kring->nr_hwtail);