prios_xa
#define prios_xa(chains) ((chains)->prios_xa)
struct xarray prios_xa;
err = xa_alloc(&prios_xa(chains), &prio_s->xa_idx, prio_s,
xa_erase(&prios_xa(chains), prio_s->xa_idx);
xa_erase(&prios_xa(chains), prio->xa_idx);
xa_for_each(&prios_xa(chains), idx, prio_s) {
xa_for_each(&prios_xa(chains), idx, prio_s) {
xa_init(&prios_xa(chains));
xa_destroy(&prios_xa(chains));