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1、数学与计算机科学系实验报告课程：计算机操作系统 地点：软件实验室二 时间： 2013年 5月 17 日学生姓名班级学号仪器编号组别同组姓名实验项目共享内存管理指导教师实验目的理解 Linux 关于共享内存的概念，掌握 Linux 支持进程间内存共享的系统调用。巩固掌握进程同步概念。实验要求使用共享内存来完成进程间通信。 要求建立一个利用共享内存机制的，关于经典同步问题 readers/writers 的解决方案。 writer 从用户处获得输入，然后将其写入共享内存，reader 从共享内存获取信息，然后再在屏幕上打印出来。实验环境Linux环境实验内容及实验结果请写出具体的实验步骤，并给出相
2、应的实验结果，附上编写的程序及其运行结果截图!实验步骤：1。2. 3. #include #include #include #include #include #include #include #include #include /* The union for semctl may or may not be defined for us.This code,defined in linuxs semctl() manpage,is the proper way to attain it if necessary */#if defined (_GNU_LIBRARY_)& !defin
3、ed (_SEM_SEMUN_UNDEFINED)/* union semun is defined by including */#else/* according to X/OPEN we have to define it ourselves */union semunint val;/* value for SETVAL */struct semid_ds *buf;/* buffer for IPC_STAT,IPC_SET */unsigned short int *array;/* array for GETALL,SETALL */struct seminfo *_buf;/*
4、 buffer for IPC_INFO */;#endif#define SHMDATASIZE1000#define BUFFERSIZE (SHMDATASIZE - sizeof(int)#define SN_READ 0#define SN_WRITE 1#define SN_LOCK 2int Semid = 0;void reader(int shmid);void writer(int shmid);int masterinit(void);char *standardinit(int shmid,int *semid);void delete(void);void sigde
5、lete(int signum);void locksem(int semid,int semnum);void unlocksem(int semid,int semnum);void waitzero(int semid,int semnum);void write(int shmid,int semid,char *buffer);int mysemget(key_t key,int nsems,int semflg);int mysemctl(int shmid,int semnum,int cmd,union semun arg);int mysemop(int semid,stru
6、ct sembuf *sops,unsigned nsops);int myshmget(key_t key,int size,int shmflg);void *myshmat(int shmid,const void *shmaddr,int shmflg);int myshmctl(int shmid,int cmd,struct shmid_ds *buf);int main(int argc,char *argv)char selection3;int shmid;/* 没有参数,则为 master */if(argc 2)shmid = masterinit();elseshmid
7、 = atoi(argv1);printf( do you want a writer(1) or reader(2) ?);fgets(selection,sizeof(selection),stdin);switch(selection0)case 1:writer(shmid); break;case 2:reader(shmid);break;default:printf( invalid choice, quit n);return 0;void reader(int shmid)int semid;char *buffer;buffer = standardinit(shmid,&
8、semid);printf(n reader begin to run， and the id of share memory is %d, semaphore id is %d n,shmid,semid);while(1)printf(n wait for writer to input information .);fflush(stdout);locksem(semid,SN_WRITE);printf(finish n);printf( wait for locking semaphore SN_LOCK .);fflush(stdout);locksem(semid,SN_LOCK
9、);printf(finish n);printf(received information: %s n,buffer);unlocksem(semid,SN_LOCK);unlocksem(semid,SN_READ);void writer(int shmid)int semid;char *buffer;buffer = standardinit(shmid,&semid);printf(writer begin to run，the id of share memory is %d, semaphore id is %dn,shmid,semid);while(1)char input
10、3;printf(n menu n 1.send a message n);printf( 2.quit n);printf(input your choice（1-2）:);fgets(input,sizeof(input),stdin);switch(input0)case 1:write(shmid,semid,buffer);break;case 2:exit(0);break;char *standardinit(int shmid,int *semid)void *shmdata;char *buffer;shmdata = myshmat(shmid,0,0);*semid =
11、*(int *)shmdata;buffer = shmdata + sizeof(int);return buffer;int masterinit(void)union semun sunion;int semid,shmid;void *shmdata;/* 首先：我们要创建信号量 */semid = mysemget(IPC_PRIVATE,3,SHM_R|SHM_W);Semid = semid;/* 当进程离开时，删除信号量 */atexit(&delete);signal(SIGINT,&sigdelete);/* 信号量 SN_READ 初始化为 1(锁定)，SN_WRITE
12、初始化为 0（未锁定）*/* 信号量 SN_LOCK 初始化为 1（锁定）*/ sunion.val = 1;mysemctl(semid,SN_READ,SETVAL,sunion);mysemctl(semid,SN_LOCK,SETVAL,sunion);sunion.val = 0;mysemctl(semid,SN_WRITE,SETVAL,sunion);/* 现在创建一块共享内存 */shmid = myshmget(IPC_PRIVATE,SHMDATASIZE,IPC_CREAT|SHM_R|SHM_W);/* 将该共享内存映射进进程的虚存空间 */shmdata = mys
13、hmat(shmid,0,0);/* 将该共享内存标志为已销毁的，这样在使用完毕后，将被自动销毁*/myshmctl(shmid,IPC_RMID,NULL);/* 将信号量的标识符写入共享内存，以通知其它的进程 */*(int *)shmdata = semid;printf(* begin to run, and semaphore id is %d n,shmid);return shmid;void delete(void)printf(n quit; delete the semaphore %d n,Semid);union semun senion;senion.val=0;if(mysemctl(Semid,0,IPC_RMID,senion) = -1)printf(Error releasing semaphore. n);void sigdelete(int s
