与main（）进行线程同步

Question

main()
{
    i=9000000000;      // to synchronize thread with while loop
    while(i)i--;      //if i don't use these two lines then my program terminates before thread starts.
    udp_socket();
    fun();
}

udp_socket()
{ 
    // open a udp socket then create thread
    pthread_create(tid1,NULL,fun2,(int *)socket_descriptor2);
}

fun()
{
}

fun2(int socket_descriptor2)
{
    while(1)
    {
    }
}

1. i opened a UDP socket then create a thread ,inside thread a while loop is continuosly recieving data on the defined ip and port.

2. My thread stop working when main terminates.....

3. i want to execute my thread continuously even when the main() terminates OR my main() also execute continuously without termination .

how can i implement this?

Answer 1

If you don't want your main to terminate too early, make it at least waiting for thread termination. Suppose that you have tid1 accessible in your main, a simple call to pthread_join(tid1,NULL) will let the main thread waits.

Answer 2

In below example main waits for thread to complete ( fun2 to return). fun2 returns when you enter an integer on stdin .

#include <stdio.h>
#include <pthread.h>

void fun() {
  printf("Hello from fun\n");
}

void fun2() {
  int a;
  scanf("%d", &a);
}

pthread_t udp_socket() {
  pthread_t tid;
  pthread_create(&tid,NULL,fun2,NULL);
  return tid;
}

int main() {
  void * ret = NULL;
  pthread_t t = udp_socket();
  fun();
  if(pthread_join(t, &ret)) {             // Waits for thread to terminate
    printf("Some Error Occurred\n");
  }
  else {
    printf("Successfully executed\n");
  }

Here is more information about pthread_join .

Answer 3

i want to execute my thread continuously even when the main() terminates

To do so exit int main() by calling pthread_exit() :

int main(void)
{
  ...

  pthread_exit(NULL); /* This call exits main() and leaves all other thread running. */

  return 0; /* Is never reached, it's just there to silence the compiler. */
}