linux c编程——信号量

朱雀 2022-11-26 15:58 263阅读 0赞

# 信号量 #

信号量是进化版的互斥量，允许多个线程访问共享资源

# 例子 #

#include <stdio.h>
    #include <unistd.h>
    #include <pthread.h>
    #include <stdlib.h>
    
    pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
    pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
    
    int beginnum = 1000;
    
    typedef struct _ProdInfo{ 
        int num;
        struct _ProdInfo *next;
    }ProdInfo;
    
    ProdInfo *Head = NULL;
    
    void *thr_producter(void *arg){ 
        //负责在链表添加数据
        while (1)
        { 
            ProdInfo * prod = malloc(sizeof(ProdInfo));
            prod->num = beginnum++;
            printf("----%s----self=%lu----%d\n",__FUNCTION__,pthread_self(),prod->num);
            pthread_mutex_lock(&mutex);
            //add to list
            prod->next = Head;
            Head = prod;
            pthread_mutex_unlock(&mutex);
            //发起通知
            pthread_cond_signal(&cond);
            sleep(rand()%4);
        }
        return NULL;
    }
    
    void *thr_customer(void *arg){ 
        ProdInfo * prod = NULL;
        while (1)
        { 
            //取链表的数据
            pthread_mutex_lock(&mutex);
            while(Head == NULL){ 
                pthread_cond_wait(&cond,&mutex);//在此之前必须先加锁
            }
            prod = Head;
            Head = Head->next;
            printf("----%s----self=%lu----%d\n",__FUNCTION__,pthread_self(),prod->num);
            pthread_mutex_unlock(&mutex);
            sleep(rand()%4);
            free(prod);
        }
        return NULL;
    }
    
    int main(int argc, char const *argv[])
    { 
        pthread_t tid[2];
        pthread_create(&tid[0],NULL,thr_producter,NULL);
        pthread_create(&tid[1],NULL,thr_customer,NULL);
        pthread_create(&tid[2],NULL,thr_customer,NULL);
    
        pthread_join(tid[0],NULL);
        pthread_join(tid[1],NULL);
        pthread_join(tid[2],NULL);
        pthread_mutex_destroy(&mutex);
        pthread_cond_destroy(&cond);
        return 0;
    }

## 输出 ##

----thr_producter----self--140546015598336----num---100
    ----thr_customer----self--140546007205632----num---100
    ----thr_producter----self--140546015598336----num---101
    ----thr_customer----self--140546007205632----num---101
    ----thr_producter----self--140546015598336----num---102
    ----thr_customer----self--140546007205632----num---102
    ----thr_producter----self--140546015598336----num---103
    ----thr_customer----self--140546007205632----num---103
    ----thr_producter----self--140546015598336----num---104
    ----thr_customer----self--140546007205632----num---104
    ----thr_producter----self--140546015598336----num---105
    ----thr_customer----self--140546007205632----num---105
    ----thr_producter----self--140546015598336----num---106
    ----thr_customer----self--140546007205632----num---106