操作系统实验报告 进程管理.doc

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05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试验五、进程同步与共享内存管理 指导教师 实验目的1、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。2、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。 实验环境实验内容及实验结果请写出具体的实验步骤，并给出相应的实验结果，附上编写的程序及其运行结果截图!实验步骤：1）关于共享内存的系统调用 程序首先调用shmget（）函数建立一块共享内存，大小为1024个字节，该函数返回创建的共享内存的标识符。然后fork一个子进程，子进程调用shmat（）函数将该共享内存连接（attach）到自己的虚存空间，即可通过普通的内存写操作（例如strcpy等），在该共享内存写入一个字符串，然后调用shmdt（）函数断开（detach）与该共享内存的连接。 在这段时间里，父进程sleep，等待子进程完成上述操作，然后调用shmctl（）函数得到关于这块共享内存的相关信息，并打印出来。然后调用shmat（）函数将这块共享内存连接（attach）到自己的虚存空间，即可通过普通的内存读操作（例如printf等）,将该共享内存中的字符串读出来。最后，调用shmctl（）函数，销毁该共享内存。 xin1.c /* xin1.c 一个简单的使用共享内存的例子 */ 2、读者写者问题编写一个利用共享内存来传递信息的程序，一个writer，一个reader，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。用信号量（semaphore）来解决这个程序对于共享内存进行操作的同步问题,使用两个信号量，一个用于读（SN_READ），一个用于写（SN_WRITE）。SN_READ初始化为0，SN_WRITE初始化为1。即SN_READ这个信号量在最初的时候就是被锁住的，而SN_WRITE这个信号量则不是。writer在往共享内存里写信息时，首先要锁定SN_WRITE信号量。在写完之后，释放SN_READ信号量，使得reader 可以读取该信息；锁定SN_WRITE这个信号量，是为了防止writer多次打印共享内存中的信息。reader读取共享内存的信息时，相应地要先锁定SN_READ这个信号量，读取信息后，释放SN_WRITE这个信号量，使得writer又可以往共享内存里面写入信息。 /* xin2.c 一个利用共享内存进行进程通信的程序 */ 3、改进上面的读者写者程序，使得程序能够支持任意数目的reader和writer。#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_)& !defined (_SEM_SEMUN_UNDEFINED) /* union semun is defined by including */ #else /* according to X/OPEN we have to define it ourselves */ union semun int 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; /* buffer for IPC_INFO */ ; #endif #define SHMDATASIZE 1000 #define BUFFERSIZE (SHMDATASIZE - sizeof(int) #define SN_READ 0 #define SN_WRITE 1 #define SN_LOCK 2 int Semid = 0; void reader(int shmid); void writer(int shmid); int masterinit(void); char *standardinit(int shmid,int *semid); void delete(void); void sigdelete(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,struct 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(); else shmid = 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,&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); 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 input3; 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 = *(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 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 = myshmat(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 signum) /* Calling exit will conveniently trigger the normal delete item. */ exit(0); void locksem(int semid,int semnum) struct sembuf sb; sb.sem_num = semnum; sb.sem_op = -1; sb.sem_flg = SEM_UNDO; mysemop(semid,&sb,1); void unlocksem(int semid,int semnum) struct sembuf sb; sb.sem_num = semnum; sb.sem_op = 1; sb.sem_flg = SEM_UNDO; mysemop(semid,&sb,1); void waitzero(int semid,int semnum) struct sembuf sb; sb.sem_num = semnum; sb.sem_op = 0; sb.sem_flg = 0; /* No modification so no need to undo */ mysemop(semid,&sb,1); void write(int shmid,int semid,char *buffer) printf(n wait for reader to read in information .); fflush(stdout); locksem(semid,SN_READ); printf(finish; wait for locking semaphore SN_LOCK.n); fflush(stdout); locksem(semid,SN_LOCK); printf(please input information:); fgets(buffer,BUFFERSIZE,stdin); unlocksem(semid,SN_LOCK); unlocksem(semid,SN_WRITE); int mysemget(key_t key,int nsems,int semflg) int retval; retval = semget(key,nsems,semflg); if(retval = -1) printf(semget key %d,nsems %d failed: %s ,key,nsems,strerror(errno); exit(255); return retval; int mysemctl(int semid,int semnum,int cmd,union semun arg) int retval; retval = semctl(semid,semnum,cmd,arg); if(retval = -1) printf(semctl semid %d,semnum %d,cmd %d failed: %s,semid,semnum,cmd,strerror(errno); exit(255); return retval; int mysemop(int semid,struct sembuf *sops,unsigned nsops) int retval; retval = semop(semid,sops,nsops); if(retval = -1) printf(semop semid %d (%d