static int can_go = 0;
static pthread_mutex_t go_mtx = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t wait_cond = PTHREAD_COND_INITIALIZER;

void set_go( void )
{
    pthread_mutex_lock( &go_mtx );
    can_go = 1;
    pthread_cond_signal(&wait_cond);
    pthread_mutex_unlock( &go_mtx );
}

int wait_go( void )
{
    pthread_mutex_lock( &go_mtx );
    while(can_go == 0)
    {
        printf("beging waiting ... n");
        pthread_cond_wait(&wait_cond, &go_mtx);
        printf("waiting donen");
    }
    printf("outside of while waiting !!!n");
    pthread_mutex_unlock( &go_mtx );
}

void *run_thread(viod *ptr)
{
    ..............
    if (is_sync_thread){  //if this is a special sync thread, do something and trigger other threads
            .............
            set_go();
    }
    else{   //this is worker, wait for sync thread finish and set_go()
        wait_go()
        ....................
    }
}

beging waiting ...
beging waiting ...
beging waiting ...
beging waiting ...
beging waiting ...
 wait done
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!
outside of while waiting !!!