操作系统哲学家就餐问题实验报告

1、-1-1-北京邮电大学操作系统实验-实验报告班号：姓名：学号：实验日期：20门门18实验名称：哲学家就餐问题（避免死锁）一、实验目的1、熟悉LINUX的基本环境，了解LINUX下进程和线程的实现三、实验内容（1）安装LINUX；（2）熟悉UNIX/LINUX的常用基本命令如Is、who、wc、pwd、ps、pstree、top,cat,cd,chgrp,chmod,chown,comm,cmp,cp,rm,diff,mv,rmdir等，了解系统的坏境。（3）利用pthread及系统的信号量（semaphore,h）,实现哲学家进餐问题（避免死锁）：四、项目要求及分析假如所有的诉学家都同时拿起左

2、侧筷子，看到右侧筷子不可用，又都放下左侧筷子，等一会儿，又同时拿起左侧筷子，如此这般，永远重复。对于这种情况，即所有的程序都在无限期地运行，但是都无法取得任何进展，即出现饥饿，所有哲学家都吃不上饭。规定在拿到左侧的筷子后，先检查右面的筷子是否可用。如果不可用，则先放下左侧筷子，等一段时间再重复整个过程。分析：当出现以卞情形，在某一个瞬间，所有的哲学家都同时启动这个算法，拿起左侧的筷子，而看到右侧筷子不可用，又都放下左侧筷子，等一会儿，又同时拿起左侧筷子如此这样永远重复下去。对于这种情况，所有的程序都在运行，但却无法取得进展，即出现饥饿，所有的哲学家都吃不上饭。解决死锁问题:为了避免死锁，把哲学

3、家分为三种状态，思考，饥饿，进食，并且一次拿到两只筷子，否则不拿。仅当一个哲学家左右两边筷子都可用时，才允许他拿筷子。这样要么一次占有两只筷子在吃面，然后释放所有资源；要么不占用资源。这样就不会导致死锁了。五、具体实现5.1、流程图（参考）5.2、添加函数的代码(所用到的各子函数)voidp_operate(intsemid,ushortseiraium)structsembufthesops;thesops.sem_num二seninum;thesopssem_op=l;thesops.SEm_flg二SEM_UND0;/thesopssem_flg=0:semop(semid,&theso

4、ps,1);voidvoperate(intsemid,ushortseiraium)structsembufthesops;thesops.sem_num二seninum;thesopssem_op=l;thesops.SEm_flg二SEM_UND0;/thesopssem_flg=0;semop(semid,&thesops,1);voidthink(intargi)#%d,Iwillthinkfor%dprintfClmphilosopher#%d,Iwillthinkfor%dsecondsnv,argi,argi+THINKTINE);sleep(argi+THINKTM);voi

5、deat(intargi)printf(/ZImphilosopher#%d,Iwill已atfor%dsecondsnz/,argi,argi+EATTIME);sleep(argi+EATTIME);voidtest(intargi,char*state,intsemid)if(stateargi=HUNGRY&stateLEFTI=EATING&stateRIGHTEATING)stateargiSEATING;printf(/zHehe,philosopher#%dcan已atnown，/,argi);v_operate(semid,argi);)else辻(stateargi!二HU

6、NGRY)printf(zzFaint,philosopher#%ddontwantto已atnz，,argi);elseprintfCOh,philosopher#%dcanteatnow!n,argi);voidtake_forks(intargi,char*state,intsemid)properate(semid,PhNum);stateargiHUNGRY;printf(“Philosopher#%dishungryCanheEat.n?，,argi);test(argi,statsemid);v_operate(semid,PhNum);properate(semid,argi)

7、;voidput_forks(intargi,char*state,intsemid)properate(semid,PhNum);stateargi=THINKING;printf(“Philosopher#%dEat0KCanhisneighbours已at.nargi);test(LEFT,statsemid);test(RIGHT,state,semid);v_operate(semid,PhNum);voidphilosopher(intargi,char*state,intsemid)while(1)-4-4think(argi);take_forks(argi,state,sem

8、id);eat(argi);put_forks(argi,state,semid);)5.3、修改原有函数部分代码(头文件变量定义主程序)#include#include#include#include#includesignalh#include#include#includestdlibh#definePhNum#defineLEFT#defineRIGHT5(PhNum+argil)%PhNum(argi+l)%PhNum#defineTHINKING0#defineHUNGRY1#defineEATING2#defineTHINKTINE4#defineEATTINE3unionsei

9、nunintval;struetsemid_ds*buf;ushort*array;intmain(intargc,char*argv)intsemkey,shmkey,semid,shmid,fori,forki,mynum;char*state;unionsemunargl;structshmid_dsarg2;ushortarrayPhNum+1;if(semid=semget(IPC.PRIVATE,PhNum+1,06001IPC.CREAT)二二一1)perror(zzSemgeterror!”)；exit(l);辻(shmid=shmget(IPC.PRIVATE,PhNum,0

10、6001IPC.CREAT)二二T)semct1(semid,0,IPC_RMID,argl);perror(Z/Shmgeterror!“)；exit(l);)arrayPhNum=l;for(fori=0:foriPhIIum;fori+)arrayfori=0:/*设置信号量数组初值*/arglarray二array;辻(semct1(semid,PhNum+1,SETALL,argl)=l)/*设置各信号量的初始值*/semct1(semid,0,IPC_RMID,argl);shmct1(shmid,IPC_RMID,&arg2);perrorCSetdefaulterror1);e

11、xit(l);if(state=shmat(shmid,0,0)=(char*)-1)/*将共享内存映射到当前进程地址空间*/semct1(semid,0,IPC_RMID,argl);shmct1(shmid,IPC_RMID,&arg2);perror(Shmaterror!);exit(l);)for(fori=0;foriPhNum;fori+)stateforiTHINKING;/*初始化状态数组*/signal(SIGINT,SIG_IGN);/*将进程对中断信号的处理设为忽略*/for(fori=l;fori=PhNum;fori+)/*创建5个哲学家子进程*/wh订e(fork

12、i=fork0)=1);辻(!forki)/*子进程执行代码*/mynum=foril;signal(SIGINT,SIG.DFL);/*设置子进程对SIGINT信号的处理过程*/-4-4break;辻(forki)vdiile(wait(char*)0)!=1);/*等待子进程执行结束，此处的(char*)0相当于NULL,即忽略返回状态*/semct1(semid,0,IPC_RMID,argl);shmdt(state);shmct1(shndd,IPC_RMID,&arg2);printf(z/nTmmonitor.Allisovern);)elsephilosopher(mynum,

13、state,semid);/*子进程调用*/六、调试运行结果唾)厲&创盟11月21日星期一10:21UfQmuyeTOQmuyemuye-laptop:文件(F)=6(V)终床E斜助(H)muy&?iTfuye-laptop:Sgccphilosopher.cImuyerouye-laptop：-S./a.outII*!philosopherImphilosophermuy&?iTfuye-laptop:Sgccphilosopher.cImuyerouye-laptop：-S./a.outII*!philosopherImphilosopherrmphilosopherInphilosoph

14、erImphilosopher#2.1willthink*14willthink#3,1willthink#4.1willthink*9,1willthinkfor6secondsfor5secondsfor7secondsfor8secondsfor4secondsPhilosopher#eishungry.canheeat.iHeherphilosophercaneatnowphilosopher#8,1willeatfor3secondsPhilosopher#1ishungry.Canheeat.Oh,philosopher#1canteatnow!Philosopher#2ishun

15、gry.canheeat.Hehe,philosopher#2caneatnowImphilosopher#2,1willeatfor5secondsPhilosopher#3ishungry.canheeat.:0h,philosopher#3canteatnow!.PhilosophereatO.K.CanhisneighbourseatFaint,philosopher#4dontwanttoeatOh,philos叩her#1canteatnow!rmphilosopher#8,1willthinkfor4secondsPhilosopher#4ishungry.Canheeat.Heherphllosopher#4caneatnow-HImph讥osopher#4,1willeatfor7secondsjPhilosopher2eatO.K.Canhisneighbourseat.Hehe.philosopher#1caneatnowOh,philosopher#3canteatnow!Imphilosopher#2,1willthinkfor6secondsll*mphilosopher#1,1willeatfor4seconds(PhilosopherMishungry