linux信号量例子-白红宇

linux信号量例子

阅读量：4966 次

发布时间：2019-06-12

本文共 4071 字，大约阅读时间需要 13 分钟。

semaphore.h 提供的是 POSIX 标准定义的 semaphore 接口,而 sys/sem.h 里提供的是符合 System V 标准的 semaphore接口（semget, semop, ...)，这些接口都比较老了， linux提供主要是为了兼容老代码

/** @file  main628.cpp*  @note   System Technology Co., Ltd. All Right Reserved.*  @brief*  @author *  @date   2019-6-28*  @note   v1.0.0 Created*  @history*  @warning*/#include 
     
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          #define NUM 5int queue[NUM];sem_t blank_number, product_number;void *producer(void *arg){    int p = 0;    while (1) {        sem_wait(&blank_number);        queue[p] = rand() % 1000 + 1;        printf("Produce %d\n", queue[p]);        sem_post(&product_number);        p = (p+1)%NUM;        sleep(rand()%5);    }}void *consumer(void *arg){    int c = 0;    while (1) {        sem_wait(&product_number);        printf("Consume %d\n", queue[c]);        queue[c] = 0;        sem_post(&blank_number);        c = (c+1)%NUM;        sleep(rand()%5);    }}int main(int argc, char *argv[]){    pthread_t pid, cid;    sem_init(&blank_number, 0, NUM);    sem_init(&product_number, 0, 0);    pthread_create(&pid, NULL, producer, NULL);    pthread_create(&cid, NULL, consumer, NULL);    pthread_join(pid, NULL);    pthread_join(cid, NULL);    sem_destroy(&blank_number);    sem_destroy(&product_number);    return 0;}

/*!* Email: xmain@gmail.com* Auth: c* Date: 2019-6-30* File: semaphoreTest.cpp* Class: %{Cpp:License:ClassName} (if applicable)* Brief:* Note: */#include 
     
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           sem_t bin_sem;void *thread_function1(void *arg){ printf("thread_function1--------------sem_wait\n"); sem_wait(&bin_sem); printf("sem_wait\n"); while (1) { printf("thread_function1\n"); }}void *thread_function2(void *arg){ printf("thread_function2--------------sem_post\n"); sem_post(&bin_sem); printf("sem_post\n"); while (1) { printf("thread_function2\n"); }}int main(){ int res; pthread_t a_thread, a_thread2; void *thread_result; res = sem_init(&bin_sem, 0, 0); if (res != 0) { perror("Semaphore initialization failed"); } printf("sem_init\n"); res = pthread_create(&a_thread, NULL, thread_function1, NULL); if (res != 0) { perror("Thread creation failure"); } //printf("thread_function1\n"); sleep (5); printf("sleep\n"); res = pthread_create(&a_thread2, NULL, thread_function2, NULL); if (res != 0) { perror("Thread creation failure"); } while (1) { printf("main\n"); }}

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           using namespace std;//用户从终端输入任意字符然后统计个数显示，输入end则结束//使用多线程实现：主线程获取用户输入并判断是否退出，子线程计数char buf[100]={ 0};static int flag = 0;sem_t sem;// 子线程程序，作用是统计buf中的字符个数并打印void *func(void*arg){ // 子线程首先应该有个循环 // 循环中阻塞在等待主线程激活的时候，子线程被激活后就去获取buf中的字符 // 长度，然后打印；完成后再次被阻塞 printf("func before 1th wait\n"); sem_wait(&sem); printf("func after 1th wait\n"); while(flag==0) { printf("长度为：%d.\n",strlen(buf)); memset(buf, 0, sizeof(buf)); printf("func before 2th wait\n"); sem_wait(&sem); printf("func after 2th wait\n"); } pthread_exit(NULL);}int main(void){ int ret=-1; pthread_t th; sem_init(&sem,0,0); ret=pthread_create(&th,NULL,func,NULL); if (ret != 0) { printf("pthread_create error.\n"); return -1; } printf("输入一个字符串,以回车结束.\n"); while(scanf("%s",buf)) { // 去比较用户输入的是不是end，如果是则退出，如果不是则继续 if(!strncmp(buf,"end",3)) { printf("输入的字符串为：%s",buf); flag=1; printf("main before 1th wait\n"); sem_post(&sem); printf("main after 1th wait\n"); break; } // 主线程在收到用户收入的字符串，并且确认不是end后 // 就去发信号激活子线程来计数。 // 子线程被阻塞，主线程可以激活，这就是线程的同步问题。 // 信号量就可以用来实现这个线程同步 printf("main before 2th wait\n"); sem_post(&sem); printf("main after 2th wait\n"); } // 回收子线程 printf("等待回收子线程\n"); ret = pthread_join(th, NULL); if (ret != 0) { printf("pthread_join error.\n"); exit(-1); } printf("子线程回收成功\n"); sem_destroy(&sem); return 0;}