条件变量的使用

#include <pthread.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
pthread_mutex_t mutex; 
pthread_cond_t cond; 
int cnt = 0; 
void* fun1(void* argv){
	fprintf(stdout, "enter fun1\n");
	pthread_mutex_lock(&mutex);
	while(cnt < 10){
		//执行下面的语句后，mutex会被释放，可以供其他的线程使用
		pthread_cond_wait(&cond, &mutex);
	}
	fprintf(stdout, "cnt is %d\n", cnt);
	pthread_mutex_unlock(&mutex);
	fprintf(stdout, "leave fun1\n");
}
void* fun2(void* argv){
	fprintf(stdout, "enter fun2\n");
	pthread_mutex_lock(&mutex);
	cnt = 10; 
	//唤醒被cond阻塞的线程
	pthread_cond_signal(&cond);
	pthread_mutex_unlock(&mutex);
	fprintf(stdout, "leave fun2\n");
}
int main(){	
	int ret; 
	if(( ret = pthread_mutex_init(&mutex, NULL)) != 0){
		fprintf(stderr, "initialize mutex error. msg:%s\n", strerror(ret));
	}
	if(( ret = pthread_cond_init(&cond, NULL)) != 0){
		fprintf(stderr, "initialize cond error. msg:%s\n", strerror(ret));
	}
	pthread_t p1, p2; 
	if((ret = pthread_create(&p2, NULL, fun2, NULL))){
		fprintf(stderr, "create thread 2 error\n"); 
	}
	if((ret = pthread_create(&p1, NULL, fun1, NULL))){
		fprintf(stderr, "create thread 1 error\n"); 
	}
	pthread_join(p1, NULL);
	pthread_join(p2, NULL);
	return 0; 
}