__futex_hash
__futex_hash(union futex_key *key, struct futex_private_hash *fph, struct futex_private_hash **fph_p);
hb_new = __futex_hash(&this->key, new, NULL);
hb = __futex_hash(key, NULL, &fph);
return (struct futex_bucket_ref){ .hb = __futex_hash(key, NULL, NULL), .fph = NULL };