UMTX_OP_SHM
error = _umtx_op(NULL, UMTX_OP_SHM, UMTX_SHM_ALIVE,
_umtx_op(NULL, UMTX_OP_SHM, UMTX_SHM_DESTROY, key, NULL);
fd = _umtx_op(NULL, UMTX_OP_SHM, doalloc ? UMTX_SHM_CREAT :
[UMTX_OP_SHM] = __umtx_op_shm,