pthread_cond_wait()和pthread_cond_signal()的调用顺序是什么？

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

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
int ready = 0;

void* producer(void* arg) {
    pthread_mutex_lock(&mutex);
    ready = 1; // 设置条件为真
    pthread_cond_signal(&cond); // 通知等待的线程
    pthread_mutex_unlock(&mutex);
    return NULL;
}

void* consumer(void* arg) {
    pthread_mutex_lock(&mutex);
    while (ready == 0) {
        pthread_cond_wait(&cond, &mutex); // 等待条件成立
    }
    printf("Condition met!\n");
    pthread_mutex_unlock(&mutex);
    return NULL;
}

int main() {
    pthread_t producer_thread, consumer_thread;

    pthread_create(&producer_thread, NULL, producer, NULL);
    pthread_create(&consumer_thread, NULL, consumer, NULL);

    pthread_join(producer_thread, NULL);
    pthread_join(consumer_thread, NULL);

    return 0;
}

while (ready == 0) {
    pthread_cond_wait(&cond, &mutex);
}