pthread_rwlock
#define THR_RWLOCK_INITIALIZER ((struct pthread_rwlock *)NULL)
#define THR_RWLOCK_DESTROYED ((struct pthread_rwlock *)1)
roundup(sizeof(struct pthread_rwlock), CACHE_LINE_SIZE));
memset(prwlock, 0, sizeof(struct pthread_rwlock));
_Static_assert(sizeof(struct pthread_rwlock) <= THR_PAGE_SIZE_MIN,
struct pthread_rwlock;
typedef struct pthread_rwlock *pthread_rwlock_t;