linux c++ 多线程同步

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <string>

pthread_cond_t cond1;
pthread_cond_t cond2;
pthread_mutex_t block1;
pthread_mutex_t block2;
pthread_mutex_t numBlock = PTHREAD_MUTEX_INITIALIZER;
int num = 0;
void *display(void *para) {
    int i = 0;
    while (1) {
        pthread_cond_wait(&cond1, &block1);
        pthread_mutex_lock(&numBlock);
        num++;
        pthread_mutex_unlock(&numBlock);
        sleep(1);
        printf("display num==[%d]\n", num);
        pthread_cond_signal(&cond2);
    }
}

int main(int argc, char const *argv[]) {
    pthread_t id;
    pthread_cond_init(&cond1, NULL);
    pthread_cond_init(&cond2, NULL);
    pthread_create(&id, NULL, display, NULL);
    while (1) {
        pthread_mutex_lock(&numBlock);
        num++;
        pthread_mutex_unlock(&numBlock);
        sleep(1);
        printf("main num+++[%d]\n", num);
        pthread_cond_signal(&cond1);
        pthread_cond_wait(&cond2,&block2);
    }
    pthread_join(id, NULL);
    return 0;
}