spmc_steal
int spmc_steal(struct spmc __arena *spmc, u64 *val);
ret = spmc_steal(spmc, &val);
ret = spmc_steal(spmc, &val);
ret = spmc_steal(spmc, &val);
ret = spmc_steal(spmc, &newval);
ret = spmc_steal(spmc, &val);
ret = spmc_steal(spmc, &newval);