条件锁pthread_cond_t

（1）pthread_cond_wait的使用

等待线程
1. 使用pthread_cond_wait前要先加锁
2. pthread_cond_wait内部会解锁，然后等待条件变量被其它线程激活
3. pthread_cond_wait被激活后会再自动加锁

（2）pthread_cond_signal的使用

激活线程：
1. 加锁（和等待线程用同一个锁）
2. pthread_cond_signal发送信号
3. 解锁
激活线程的上面三个操作在运行时间上都在等待线程的pthread_cond_wait函数内部。

#include
#include
#include struct msg {
struct msg* next;
int data;
};
struct msg* tasks = NULL;

pthread_mutex_t mu = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
void* TestWait(void* args) {
pthread_mutex_lock(&mu);//这里开始时加锁
while() {
pthread_cond_wait(&cond, &mu);//该函数首先将当前线程加入内部的等待列表中，然后释放锁，接着休眠并阻塞。。。。。直到有外部信号（pthread_cond_signal)通知，会加锁然后返回。
printf("%ld wake up\n", pthread_self());
if (tasks != NULL) {
struct msg* tsk = tasks;
tasks = tasks->next;
printf("tid:%ld data:%ld\n", pthread_self(), tsk->data);
free(tsk);
}
}
pthread_mutex_unlock(&mu);
pthread_exit(NULL);
}

int main() {

    pthread\_t tids\[\];  
    for(int i = ; i < ; i++) {  
            pthread\_create(&tids\[i\], NULL, TestWait, NULL);  
    }  
    sleep();

    for (int i = ; i < ; i++) {  
            pthread\_mutex\_lock(&mu);

            struct msg\* tmp = (struct msg\*) malloc(sizeof(struct msg));  
            tmp->next = tasks;  
            tmp->data = ;  
            tasks = tmp;

            pthread\_cond\_signal(&cond);  
            //pthread\_cond\_broadcast(&cond);  
            pthread\_mutex\_unlock(&mu);  
    }

    pthread\_exit(NULL);  
    return ;  

}