C语言：生产者消费者（线程-互斥量与条件变量）

#iinclude <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <pthread.h>
    
struct Msg                //共享数据
{
        int num;
        struct Msg *next;
};

struct Msg *head;

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;    //定义并初始化一个互斥量
pthread_cond_t has_data = PTHREAD_COND_INITIALIZER;    //定义并初始化一个条件变量

void err_thread(int ret,char *str)
{
        if(ret != 0){
                fprintf(stderr,"%s:%s\n",str,strerror(ret));
                pthread_exit(NULL);
        }
}

void *produser(void *arg)    //生产者
{
        while(1){
                struct Msg *food = (struct Msg *)malloc(sizeof(struct Msg));    //生产一个食物
                food->num = rand() % 1000 + 1;        //初始化食物，模拟生产了一个数据
                printf("--produser %d\n",food->num);

                pthread_mutex_lock(&mutex);          //加锁
                food->next = head;                  //写公共区域      
                head = food;
                pthread_mutex_unlock(&mutex);       //解锁

                pthread_cond_signal(&has_data);    //唤醒阻塞在条件变量 has_data上的线程

                sleep(rand() % 3);
        }
}

void *consumer(void *arg)    //消费者
{
        struct Msg *food;

        while(1){
                pthread_mutex_lock(&mutex);                    //加锁 互斥量
                if(head == NULL){    
                        pthread_cond_wait(&has_data,&mutex);    //阻塞等待条件变量，解锁
                }                                               //pthread_cond_wait 返回时，重新加锁                         

                food = head;
                head = food->next;

                pthread_mutex_unlock(&mutex);                   //解锁
                printf("-------------------consumer:%d\n",food->num);

                free(food);
                sleep(rand() % 3);
        }
}

int main()
{
        int ret;
        pthread_t pid,cid;

        srand(time(NULL));

        ret = pthread_create(&pid,NULL,produser,NULL);    //生产者线程
        if(ret != 0){
                err_thread(ret,"pthread_creat error");
        }

        ret = pthread_create(&cid,NULL,consumer,NULL);    //消费者线程
        if(ret != 0){
                err_thread(ret,"pthread_creat error");
        }

        pthread_join(pid,NULL);
        pthread_join(cid,NULL);

        return 0;
}