Break the limit of threading, segmentation fault

Question

use pthread_create to create limited number of threads running concurrently Successfully compile and run

However, after adding function pointer array to run the function, Segmentation fault

Where is wrong?

workserver number: 0 Segmentation fault

void* workserver(void *arg)
{
int status;
while(true)
{
    printf("workserver number: %d\n", (int)arg);
    (* job_queue[(int)arg])();
    sleep(3);

    status = pthread_mutex_lock(&data.mutex);
    if(status != 0)
        printf("%d lock mutex", status);
    data.value = 1;
    status = pthread_cond_signal(&data.cond);
    if(status != 0)
        printf("%d signal condition", status);
    status = pthread_mutex_unlock(&data.mutex);
    if(status != 0)
        printf("%d unlock mutex", status);
}
}


void jobadd(void (*job)())
{   
    for(int i; i<3; i++)
    {
        if(idle[i] == 0)
        {
            job_queue[i] = job;
            job;
            idle[i] = 1;
        }
    }
}
void func1()
{
    printf("func1 run");
}
void func2()
{
    printf("func2 run");
}
void func3()
{
    printf("func3 run");
}
void func4()
{
    printf("func4 run");
}

int main(int argc, char* argv[])
{
    jobadd(func1);
    jobadd(func2);
    jobadd(func3);
    jobrun();
    return 0;
}

initialize function pointer array with jobadd function

Answer 1

add more detail in the question

job_queue[i] = job

just assign a function to the function pointer array

as can not assign function pointer array directly to pthread_create

Answer 2

After placing function pointer array (* job_queue[(int)arg])(); at the end it can successfully call function with the following result even if i add a infinite loop and a sleep in func1, it will not block at func1

now i am working on how to replace existing running function with a new function using pthread_cleanup_push and pop

• workserver number: 0 func1 run
• workserver number: 2 func3 run
• workserver number: 1 func2 run
• workserver number: 0 func1 run
• workserver number: 2 func3 run
• workserver number: 1 func2 run
• workserver number: 2 workserver
• number: 0 func3 run func1 run
• workserver number: 1 func2 run
• workserver number: 0 workserver
• number: 2 func1 run func3 run
• workserver number: 1 func2 run
• workserver number: 2 workserver
• number: 0 func3 run func1 run
• workserver number: 1 func2 run
• workserver number: 0 workserver
• number: 2 func1 run func3 run

• workserver number: 1 func2 run

  while(true) { printf("workserver number: %d\n", (int)arg);

  status = pthread_mutex_lock(&data.mutex);
  
  
  //pthread_cleanup_push(
  
  
  if(status != 0)
       printf("%d lock mutex", status);
  data.value = 1;
  status = pthread_cond_signal(&data.cond);
  if(status != 0)
      printf("%d signal condition", status);
  status = pthread_mutex_unlock(&data.mutex);
  if(status != 0)
      printf("%d unlock mutex", status);
  
  
  (* job_queue[(int)arg])();
  sleep(1);
  void (* clean)(void *);
  clean = NULL;
  /*
  for(int i=0; i<4; i++)
  {
      if(idle[i] == 0)
      {
          if(fp[(int)arg] != NULL)
          {
              idle[running_number[(int)arg]] = 0; // replace its running job
              clean = fp[(int)arg];
              fp[(int)arg] = job_queue[i];
              pthread_cleanup_push(clean, NULL);
              (*fp[(int)arg])();
              pthread_cleanup_pop(1);
  
  
          idle[i] = 1;
      }
      else
      {
          fp[(int)arg] = job_queue[i];
          idle[i] = 1;
          running_number[(int)arg] = i;
          (*fp[(int)arg])();
      }
  }
  
  
  }*/
  

  }