(&t1, NULL, increment, NULL);
pthread_create(&t2, NULL, increment, NULL);
pthread_join(t1, NULL...(&t1, NULL, increment, NULL);
pthread_create(&t2, NULL, increment, NULL);
pthread_join(t1, NULL...(&t1, NULL, thread1, NULL);
pthread_create(&t2, NULL, thread2, NULL);
pthread_join(t1, NULL);...(&t1, NULL, increment, NULL);
pthread_create(&t2, NULL, increment, NULL);
pthread_join(t1, NULL...(&t1, NULL, thread1, NULL);
pthread_create(&t2, NULL, thread2, NULL);
pthread_join(t1, NULL