如果是安全的破坏pthread的障碍？ [英] When is it safe to destroy a pthread barrier?

问题描述

如果我有一个初始化pthread_barrier_t，当是安全的破坏呢？就是下面的例子安全吗？

  pthread_barrier_t屏障;
...
INT RC = pthread_barrier_wait（B）;
如果（RC = PTHREAD_BARRIER_SERIAL_THREAD和放大器;！＆安培;！RC = 0）{
  PERROR（pthread_barrier_wait）;
  出口（1）;
}如果（ID == 0）{
  如果（pthread_barrier_destroy（及（线程[t_root] .info.tmp_barrier）））{
    PERROR（pthread_barrier_destroy）;
    出口（1）;
  }
}
 

解决方案

在 pthread_barrier_wait（）的回报，所有的线程将相继命中屏障和跟进。由于只有一个线程被赋予 PTHREAD_BARRIER_SERIAL_THREAD 的返回值，就可以安全地用它来包裹有条件的破坏code，像这样：

  INT RC = pthread_barrier_wait（和b）
如果（RC == PTHREAD_BARRIER_SERIAL_THREAD）
{
    pthread_barrier_destroy（和b）;
}
 

此外，要知道， pthread_barrier_destroy（）将返回 EBUSY 的结果，如果障碍是使用（即另一个线程曾呼吁 pthread_barrier_wait（））。

If I have an initialised pthread_barrier_t, when is it safe to destroy it? Is the following example safe?

pthread_barrier_t barrier;
...
int rc = pthread_barrier_wait(b);
if (rc != PTHREAD_BARRIER_SERIAL_THREAD && rc != 0){
  perror("pthread_barrier_wait");
  exit(1);
}

if (id == 0){
  if(pthread_barrier_destroy(&(threads[t_root].info.tmp_barrier))){
    perror("pthread_barrier_destroy");
    exit(1);
  }
}

解决方案

After pthread_barrier_wait() returns, all threads will have hit the barrier and are proceeding. Since only one thread is given the PTHREAD_BARRIER_SERIAL_THREAD return value, it's safe to use that to conditionally wrap the destruction code like so:

int rc = pthread_barrier_wait(&b)
if ( rc == PTHREAD_BARRIER_SERIAL_THREAD )
{
    pthread_barrier_destroy(&b);
}

Also, be aware that pthread_barrier_destroy() will return a result of EBUSY if the barrier was in use (i.e. another thread had called pthread_barrier_wait()).

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