爱华网barrier定义：typedef union{char__size[__SIZEOF_PTHREAD_BARRIER_T];long int __align;} pthread_barrier_t;
struct pthread_barrier{unsigned intcurr_event;//等待Count用变量int lock;unsigned intleft;//Down Counterunsigned intinit_count;//Counter初始值};
barrier初始化：intpthread_barrier_init (barrier, attr, count) pthread_barrier_t *barrier; constpthread_barrierattr_t *attr; unsigned int count;{struct pthread_barrier*ibarrier;
if (__builtin_expect(count == 0, 0)) returnEINVAL;
if (attr != NULL) { struct pthread_barrierattr *iattr;
iattr = (struct pthread_barrierattr *)attr;
if (iattr->pshared !=PTHREAD_PROCESS_PRIVATE &&__builtin_expect (iattr->pshared !=PTHREAD_PROCESS_SHARED, 0)) return EINVAL; }
ibarrier = (structpthread_barrier *) barrier;
ibarrier->lock =LLL_LOCK_INITIALIZER;ibarrier->left =count;ibarrier->init_count= count;ibarrier->curr_event= 0;
return 0;}
barrier等待：intpthread_barrier_wait (barrier) pthread_barrier_t *barrier;{struct pthread_barrier*ibarrier = (struct pthread_barrier *) barrier;int result = 0;
lll_lock(ibarrier->lock);--ibarrier->left;
//这种情况下，说明已经达到了指定的等待次数//唤醒所有的等待线程//虽然对最后一个调用该函数的线程返回PTHREAD_BARRIER_SERIAL_THREAD//但是POSIX规定这是 不 定 的if(ibarrier->left == 0) { ++ibarrier->curr_event;
lll_futex_wake(&ibarrier->curr_event,INT_MAX);
result = PTHREAD_BARRIER_SERIAL_THREAD; } else { unsigned int event =ibarrier->curr_event;
lll_unlock (ibarrier->lock);
do lll_futex_wait(&ibarrier->curr_event,event); w hile (event ==ibarrier->curr_event); }
unsigned int init_count =ibarrier->init_count;
if(atomic_increment_val(&ibarrier->left) ==init_count) lll_unlock (ibarrier->lock);
returnresult;}
API函数：int pthread_barrier_init(pthread_barrier_t *barrier, constpthread_barrierattr_t *attr, unsigned int count);int pthread_barrier_wait(thread_barrier_t *barrier);int pthread_barrier_destroy(ed_barrier_t *barrier);int pthread_barrierattr_init(pthread_barrierattr_t*attr);int pthread_barrierattr_setpshared(pthread_barrierattr_t*attr, int pshared);int pthread_barrierattr_getpshared(const pthread_barrierattr_t*attr, int *pshared);
