同时启动所有线程(Starting all threads at the same time)

 我无法理解像pthread_mutex_lock / unlock和pthread_cond_wait / signal这样的条件变量 
 
 我试图创建九个threads ，并让它们同时运行，以确定哪个threads效率最高。 
 
    int threadNumber = 0;
    pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
    pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

    #define NUM_THREADS    9

    //used to store the information of each thread
    typedef struct{
        pthread_t  threadID;
        int policy;
        struct sched_param param;
        long startTime;
        long taskStartTime;
        long endTime1;
        long endTime2;
        long endTime3;
        long runTime;
        char startDate[30];
        char endDate[30];
    }ThreadInfo;

ThreadInfo myThreadInfo[NUM_THREADS];



//main function
int main(void){

   printf("running...\n");

   pthread_mutex_lock(&mutex); //lock the mutex//////
   pthread_cond_wait(&cond, &mutex); //start waiting//////


   int fifoPri = 60;
   int rrPri = 30;

   //create the 9 threads and assign their scheduling policies
   for(int i=0; i<NUM_THREADS; i++){

      if(i%3 == SCHED_OTHER){
            myThreadInfo[i].policy = SCHED_OTHER;
            myThreadInfo[i].param.sched_priority = 0;

      }
      else if (i%3 == SCHED_RR){ 
            myThreadInfo[i].policy = SCHED_RR;
            myThreadInfo[i].param.sched_priority = rrPri++; 
      }

      else{
            myThreadInfo[i].policy = SCHED_FIFO; 
            myThreadInfo[i].param.sched_priority = fifoPri++; 

      }

      pthread_create( &myThreadInfo[i].threadID, NULL, ThreadRunner, &myThreadInfo[i]);

   }

   printf("\n\n");

   pthread_mutex_unlock(&mutex) //unlock the mutex/////////
   pthread_cond_signal(&cond); //signal the threads to start////////


   //join each thread
   for(int g = 0; g < NUM_THREADS; g++){
      pthread_join(myThreadInfo[g].threadID, NULL);
   }


   //print out the stats for each thread and perform an analysis of the data
   DisplayThreadSchdStats();


   return 0;
}

...
 
 所以当主函数启动时，我lock互斥锁以确保线程在我告诉他们使用pthread_lock（＆mutex）和pthread_cond_wait（＆cond，＆mutex）之前不会启动。 
 
 然后我使用各种调度策略创建所有九个线程。 完成之后，我尝试通过使用pthread_mutex_unlock（＆mutex）和pthread_cond_signal（＆cond）来同时启动所有线程， 
 
 但是当我运行它时，它永远不会解锁线程。 主函数的“正在运行...”打印语句熄灭，但线程永远不会启动。 （threadrunner有一个函数，它们都打印出大量不同的数字，所以我可以看到它们是否启动）。 我在做pthread互斥体和pthread cond的错误是什么？ 

I'm having trouble understanding condition variables like pthread_mutex_lock/unlock and pthread_cond_wait/signal
 
I'm trying to create nine threads, and have them all run at the same time to figure out which is the most efficient.
 
    int threadNumber = 0;
    pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
    pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

    #define NUM_THREADS    9

    //used to store the information of each thread
    typedef struct{
        pthread_t  threadID;
        int policy;
        struct sched_param param;
        long startTime;
        long taskStartTime;
        long endTime1;
        long endTime2;
        long endTime3;
        long runTime;
        char startDate[30];
        char endDate[30];
    }ThreadInfo;

ThreadInfo myThreadInfo[NUM_THREADS];



//main function
int main(void){

   printf("running...\n");

   pthread_mutex_lock(&mutex); //lock the mutex//////
   pthread_cond_wait(&cond, &mutex); //start waiting//////


   int fifoPri = 60;
   int rrPri = 30;

   //create the 9 threads and assign their scheduling policies
   for(int i=0; i<NUM_THREADS; i++){

      if(i%3 == SCHED_OTHER){
            myThreadInfo[i].policy = SCHED_OTHER;
            myThreadInfo[i].param.sched_priority = 0;

      }
      else if (i%3 == SCHED_RR){ 
            myThreadInfo[i].policy = SCHED_RR;
            myThreadInfo[i].param.sched_priority = rrPri++; 
      }

      else{
            myThreadInfo[i].policy = SCHED_FIFO; 
            myThreadInfo[i].param.sched_priority = fifoPri++; 

      }

      pthread_create( &myThreadInfo[i].threadID, NULL, ThreadRunner, &myThreadInfo[i]);

   }

   printf("\n\n");

   pthread_mutex_unlock(&mutex) //unlock the mutex/////////
   pthread_cond_signal(&cond); //signal the threads to start////////


   //join each thread
   for(int g = 0; g < NUM_THREADS; g++){
      pthread_join(myThreadInfo[g].threadID, NULL);
   }


   //print out the stats for each thread and perform an analysis of the data
   DisplayThreadSchdStats();


   return 0;
}

...
 
so when the main function starts, I lock the mutex to make sure the threads don't start before I tell them to with pthread_lock(&mutex) and pthread_cond_wait(&cond, &mutex)
 
then I create all nine threads with various scheduling policies. After that's completely done, I try to tell the threads to all start at the same time using pthread_mutex_unlock(&mutex) and pthread_cond_signal(&cond)
 
But when I run this, it never unlocks the threads. The main function's "running..." print statement goes off, but the threads never start. (threadrunner has a function where they all print out a ton of different numbers so I can see if they launch). What am I doing wrong with the pthread mutex and pthread cond?

原文：https://stackoverflow.com/questions/48753142