UMEM_READY_INITING
umem_ready == UMEM_READY_INITING ? "initialization in process" :
while (umem_ready == UMEM_READY_INITING) {
umem_ready = UMEM_READY_INITING;
if (umem_ready == UMEM_READY_INITING && umem_init_thr != thr_self()) {