Linux 多线程按照线程顺序打印字符

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

int num = 0;
pthread_mutex_t mutex_lock = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond_ready = PTHREAD_COND_INITIALIZER;


void *output_chara(void *arg)
{
    int i;
    int cond_num = (int) arg;

    for (i = 0; i < 10; i++){
        pthread_mutex_lock(&mutex_lock);
        while (num != cond_num){
            pthread_cond_wait(&cond_ready, &mutex_lock);
        }

        printf("%c", 'A' + cond_num);

        num = (num + 1) % 3;

        pthread_mutex_unlock(&mutex_lock);
        pthread_cond_broadcast(&cond_ready);
    }
}

int main()
{
    int i;
    pthread_t tid[3];

    for (i = 0; i < 3; i++){
        pthread_create(&tid[i], NULL, output_chara, (void *)i);
    }

    for (i = 0; i < 3; i++){
        pthread_join(tid[i], NULL);
    }

    return 0;
}

output:

ABCABCABCABCABCABCABCABCABCABC