Pthread程序在pthread_join执行之前挂起，无法弄清楚为什么

Question

我试图用pthreads做一个练习，做一个相当简单的搜索，我把一个文本文件分成5列，5个线程每个执行搜索。在此之后，将进行合并，以确定输入是否与文本文件中的任何单个条目匹配。然而，当我运行它时，它似乎挂起了。我想我有一个各种各样的竞争条件，但是用DDD调试还没有产生任何结果。

我认为我正在正确地创建和连接pthread，但我不确定我是否正确地使用了互斥锁。

search函数在给定列中创建一个唯一值的链表，然后创建一个位掩码，用于保存找到该值的索引。无论如何，如果我运行一个标准的线性搜索，我得到7更多的结果为我的测试数据，如果我做它线程，我认为这意味着某些东西是失败的搜索或合并线程。将我的数据集的批大小从10%块减少到一次1或2个值会增加匹配的数量，但我仍然会错过正确的总数。

如果有人知道为什么程序在完成之前挂起(可能是由于搜索或合并线程)，我将非常感谢帮助。

为了简洁起见，我省略了大约一半的代码，但如果有帮助的话，我可以发布更多的代码。

void * search(void* pthread_arg){
  search_thread_param * myParams = (search_thread_param*) pthread_arg;
  int k=0; // how many searches have been done so far
  int m;
  while (k<NUM_PACKETS){
    pthread_mutex_lock(&mutex);
    if(n !=0){
      pthread_cond_wait(&search_cv, &mutex);  // mege is in progress, go to sleep
    }
    pthread_mutex_unlock(&mutex);     // release th lock so the other search threads can acquire it
    for (m =0; m < BATCH; m++)
      myParams->buffer[m] = mySearchFunction(myParams->packet_field[k+m], myParams->rule_field, unique_no[myParams->thread_id]);  // given a value, return its BV
    k=k+m;
    pthread_mutex_lock(&mutex);
    if (n==NUM_FIELDS-1) // this search thread is the only active one
      {
    n++;
    pthread_mutex_unlock(&mutex);   
    pthread_cond_signal(&merge_cv); // wake up merge thread
      } 
    else{  // not the last one goes to sleep
      n++;
      pthread_mutex_unlock(&mutex); 
    }   
  } 
  return NULL;
}
void merge_function(unsigned long b0,unsigned long b1,unsigned long b2,unsigned long b3,unsigned long b4){
  unsigned long final_BV;
  final_BV = b0 & b1 & b2 & b3 & b4;
  if( final_BV )
  int counter = 0;
    while(final_BV){
      counter++;
      final_BV = final_BV >> 1; //bit shift 
    }
    if( counter)
      printf("matched rule %in", counter);
}
void * merge (void* pthread_arg){
  merge_thread_param * myParams = (merge_thread_param*) pthread_arg;
  int k=0; // how many merges have been done so far
  int m;
  pthread_mutex_lock(&mutex);
  if (n<NUM_FIELDS) // the first batch is not ready
    pthread_cond_wait(&merge_cv, &mutex);    // go to sleep
  while (k<NUM_PACKETS){
    for (m =0; m < BATCH; m++){
      merge_function(myParams->buffer[0][m],myParams->buffer[1][m],myParams->buffer[2][m],myParams->buffer[3][m],myParams->buffer[4][m]);
    }
      printf("Merge thread: finish merging one batchn");   
      k=k+m;
      n = 0; //ready to wake up all search threads
      if(k ==NUM_PACKETS){  // the program is over
    pthread_mutex_unlock(&mutex);   
    printf("Merge thread:  I am done, found %i results, compared to %i linear search  n = %in",res,lin,n);
    return NULL;
      }
      else  {
    pthread_cond_broadcast(&search_cv);
    pthread_mutex_unlock(&mutex);
    pthread_cond_wait(&merge_cv, &mutex);    // go to sleep
      }  
  }     
  return NULL;
}
int main () {
///////setup info omitted for brevity
  // create search threads
  for (i=0; i< NUM_FIELDS; i++)
    if(pthread_create(&s_thread[i], &attr, search, (void*) &stp[i])!=0){printf("Creating Thread failed!n");}
  // create merge thread        
  if(pthread_create(&m_thread, &attr, merge, (void*) &mtp)!=0){printf("Creating Thread failed!n");}
  // join the threads
    for (i=0; i<NUM_FIELDS; i++)
    if (pthread_join(s_thread[i], NULL)==0){printf("joined thread %in",i);}
    else{printf("Joining thread %i failed!n",i);}
  if (pthread_join(m_thread, NULL)!=0){printf("joined merge thread");}
  else{printf("Joining thread failed!n");}     
  pthread_attr_destroy(&attr);
  pthread_mutex_destroy(&mutex);
  pthread_cond_destroy(&search_cv);
  pthread_cond_destroy(&merge_cv);      
  //free dat memory
  printf("finished joining all the threads");
  fflush(stdout);
  return 0;
}

Answer 1

原来问题是决定是否在合并线程中设置pthread_cond_wait的检查出错，导致合并线程在搜索线程之前执行。这意味着合并线程在搜索线程完成生成结果之前就完成了。然后，搜索线程向一个不存在的线程发出信号，并进入睡眠状态。它从未连接，因为它从未完成。好了，就这样了