Linux互斥与同步应用（三）：posix线程实现单个生产者和单个消费者模型

        【版权声明：尊重原创，转载请保留出处：blog.csdn.net/shallnet 或 .../gentleliu，文章仅供学习交流，请勿用于商业用途】

        在第一节说到了生产者消费者问题，这一节我们来实现这样一个稍作修改的模型： 初始时缓冲区为空，生产者向缓冲区写入数据，消费者在缓冲区为空的情况下睡眠，当生产者写满缓冲区一半之后后通知消费者可以开始消费，生产者开始睡眠，直到消费者消费完缓冲区一半后通知生产者可以开始生产为止，其中生产者和消费者对缓冲区的访问时互斥的。

下面来看一下实现：

#include <stdio.h>#include <pthread.h>#include <unistd.h>#define MAX_BUFFER 6int buffer = 0;pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;pthread_cond_t cond_consumer = PTHREAD_COND_INITIALIZER;pthread_cond_t cond_productor = PTHREAD_COND_INITIALIZER;void *consumer_th(void *arg){    for (;;) {        pthread_mutex_lock(&mutex);        if (buffer <= 0) {            printf("=%s->%d=====consumer wait productor to product, start sleep..., buffer=%d\n", __func__, __LINE__, buffer);            pthread_cond_wait(&cond_consumer, &mutex);//当消费者发现缓冲区为空时开始睡眠        }        buffer--; //消费者消耗一个缓冲区        printf("=%s->%d====consumer consume a buffer, buffer=%d\n", __func__, __LINE__, buffer);        if (buffer < MAX_BUFFER/2) {            pthread_cond_signal(&cond_productor); //当消费者发现缓冲区不足一半时通知生产者开始生产            printf("=%s->%d====Notify productor...,, buffer: %d\n", __func__, __LINE__, buffer);        }        pthread_mutex_unlock(&mutex);        sleep(3);    }    return NULL;}void *productor_th(void *arg){    for (;;) {        sleep(1);        pthread_mutex_lock(&mutex);        if (buffer >= MAX_BUFFER) {            printf("=%s->%d=====productor wait consumer to consume, start sleep..., buffer=%d\n", __func__, __LINE__, buffer);            pthread_cond_wait(&cond_productor, &mutex);//当缓冲区满时，暂停生产        }        buffer++;//生产者增加一个缓冲区        printf("=%s->%d====Product add a buffer..., buffer: %d\n", __func__, __LINE__, buffer);        if (buffer > MAX_BUFFER/2) {            pthread_cond_signal(&cond_consumer);//当缓冲区增加到一半时，通知消费者可以开始消费            printf("=%s->%d====Notify consumer...,, buffer: %d\n", __func__, __LINE__, buffer);        }        pthread_mutex_unlock(&mutex);    }    return NULL;}int main(int argc, const char *argv[]){    pthread_t tid_productor, tid_consumer;    if (0 != pthread_create(&tid_consumer, NULL, consumer_th, NULL)) {        printf("pthread_create failed!\n");        return -1;    }    if (0 != pthread_create(&tid_productor, NULL, productor_th, NULL)) {        printf("pthread_create failed!\n");        return -1;    }    pthread_join(tid_productor, NULL);    pthread_join(tid_consumer, NULL);    return 0;}

下面是程序运行输出结果：

=consumer_th->20=====consumer wait productor to product, start sleep..., buffer=0//消费者开始睡眠等待生产者唤醒=productor_th->54====Product add a buffer..., buffer: 1=productor_th->54====Product add a buffer..., buffer: 2=productor_th->54====Product add a buffer..., buffer: 3=productor_th->54====Product add a buffer..., buffer: 4//生产者开始写缓冲区，当写到第4（超过一半）个通知消费者=productor_th->58====Notify consumer...,, buffer: 4=consumer_th->25====consumer consume a buffer, buffer=3//消费者一边消费缓冲区=productor_th->54====Product add a buffer..., buffer: 4//生产者一边生产缓冲区=productor_th->58====Notify consumer...,, buffer: 4=productor_th->54====Product add a buffer..., buffer: 5=productor_th->58====Notify consumer...,, buffer: 5=consumer_th->25====consumer consume a buffer, buffer=4=productor_th->54====Product add a buffer..., buffer: 5=productor_th->58====Notify consumer...,, buffer: 5=productor_th->54====Product add a buffer..., buffer: 6=productor_th->58====Notify consumer...,, buffer: 6=productor_th->49=====productor wait consumer to consume, start sleep..., buffer=6//当生产者生产缓冲区满时，开始睡眠=consumer_th->25====consumer consume a buffer, buffer=5=consumer_th->25====consumer consume a buffer, buffer=4=consumer_th->25====consumer consume a buffer, buffer=3=consumer_th->25====consumer consume a buffer, buffer=2//当消费者消费缓冲区到不足一半时，唤醒生产者开始生产=consumer_th->28====Notify productor...,, buffer: 2=productor_th->54====Product add a buffer..., buffer: 3=productor_th->54====Product add a buffer..., buffer: 4=productor_th->58====Notify consumer...,, buffer: 4=productor_th->54====Product add a buffer..., buffer: 5=productor_th->58====Notify consumer...,, buffer: 5=consumer_th->25====consumer consume a buffer, buffer=4=productor_th->54====Product add a buffer..., buffer: 5=productor_th->58====Notify consumer...,, buffer: 5=productor_th->54====Product add a buffer..., buffer: 6=productor_th->58====Notify consumer...,, buffer: 6=productor_th->49=====productor wait consumer to consume, start sleep..., buffer=6

本节源码下载：

点击打开链接