信号量示例——“生产者——消费者”实验

互斥模型

 同步模型

 生产者消费者其实是用了两种模型，就是先同步再互斥，就是首先要先由生产者生产产品，后面消费者才能消费产品，同时生产和消费这个过程是要互斥的。

#include<semaphore.h>
#include<pthread.h>
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>

#define N 10

typedef struct product
{
    char name;
}product;

product p1[N];

sem_t mutex;
sem_t synch1;
sem_t synch2;

int count = 0;

void *produce_item(void *arg)
{
    char ch = 'a';
    while (1)
    {
        printf("生产者生产一个产品
");
        sem_wait(&synch1);
        sem_wait(&mutex);
        p1[count].name= ch;
        sleep(1); 
        printf("------------------
");
        printf("%c产品已入库
",ch);
        ch++;
        count++;
        printf("产品个数%d
",count);
        printf("------------------
");
        sem_post(&mutex);
        sem_post(&synch2);
        sleep(1);
    }
}

void *custom_item(void *arg)
{
    sleep(5);
    while (1)
    {
        sem_wait(&synch2);
        sem_wait(&mutex);
        count--;
        printf("消费者消费一个产品
");
        printf("产品个数%d
",count);
        sem_post(&mutex);
        sem_post(&synch1);
        sleep(2);
    }
    
}
int main(int argc, char const *argv[])
{
    pthread_t producer;
    pthread_t customer;
    if(sem_init(&mutex,0,1) == -1)
    {
        perror("sem_init mutex");
        exit(1);
    }
    if(sem_init(&synch1,0,N) == -1)
    {
        perror("sem_init synch1");
        exit(1);
    }
    if(sem_init(&synch2,0,0) == -1)
    {
        perror("sem_init stnch2");
        exit(1);
    }
    if(pthread_create(&producer,NULL,produce_item,NULL) != 0)
    {
        perror("pthread_create producer");
        exit(1);
    }
    if(pthread_create(&customer,NULL,custom_item,NULL) == -1)
    {
        perror("pthread_create custom");
        exit(1);
    }
    pthread_join(producer,NULL);
    pthread_join(customer,NULL);
    sem_destroy(&mutex);
    sem_destroy(&synch1);
    sem_destroy(&synch2);
    return 0;
}

运行结果：