in src/pthread_mutex.c [172:181]
static inline int _pthread_mutex_init(pthread_mutex_t *mutex,
const pthread_mutexattr_t *attr, uint32_t static_type);
typedef union mutex_seq {
uint32_t seq[2];
struct { uint32_t lgenval; uint32_t ugenval; };
struct { uint32_t mgen; uint32_t ugen; };
uint64_t seq_LU;
uint64_t _Atomic atomic_seq_LU;
} mutex_seq;