操作系統(tǒng)哲學(xué)家就餐問題實(shí)驗(yàn)報(bào)告

1、-1-1-北京郵電大學(xué)操作系統(tǒng)實(shí)驗(yàn)-實(shí)驗(yàn)報(bào)告班號(hào)：姓名：學(xué)號(hào)：實(shí)驗(yàn)日期：20門門18實(shí)驗(yàn)名稱：哲學(xué)家就餐問題（避免死鎖）一、實(shí)驗(yàn)?zāi)康?、熟悉LINUX的基本環(huán)境，了解LINUX下進(jìn)程和線程的實(shí)現(xiàn)三、實(shí)驗(yàn)內(nèi)容（1）安裝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，了解系統(tǒng)的壞境。（3）利用pthread及系統(tǒng)的信號(hào)量（semaphore,h）,實(shí)現(xiàn)哲學(xué)家進(jìn)餐問題（避免死鎖）：四、項(xiàng)目要求及分析假如所有的訴學(xué)家都同時(shí)拿起左

2、側(cè)筷子，看到右側(cè)筷子不可用，又都放下左側(cè)筷子，等一會(huì)兒，又同時(shí)拿起左側(cè)筷子，如此這般，永遠(yuǎn)重復(fù)。對(duì)于這種情況，即所有的程序都在無(wú)限期地運(yùn)行，但是都無(wú)法取得任何進(jìn)展，即出現(xiàn)饑餓，所有哲學(xué)家都吃不上飯。規(guī)定在拿到左側(cè)的筷子后，先檢查右面的筷子是否可用。如果不可用，則先放下左側(cè)筷子，等一段時(shí)間再重復(fù)整個(gè)過(guò)程。分析：當(dāng)出現(xiàn)以卞情形，在某一個(gè)瞬間，所有的哲學(xué)家都同時(shí)啟動(dòng)這個(gè)算法，拿起左側(cè)的筷子，而看到右側(cè)筷子不可用，又都放下左側(cè)筷子，等一會(huì)兒，又同時(shí)拿起左側(cè)筷子如此這樣永遠(yuǎn)重復(fù)下去。對(duì)于這種情況，所有的程序都在運(yùn)行，但卻無(wú)法取得進(jìn)展，即出現(xiàn)饑餓，所有的哲學(xué)家都吃不上飯。解決死鎖問題:為了避免死鎖，把哲學(xué)

3、家分為三種狀態(tài)，思考，饑餓，進(jìn)食，并且一次拿到兩只筷子，否則不拿。僅當(dāng)一個(gè)哲學(xué)家左右兩邊筷子都可用時(shí)，才允許他拿筷子。這樣要么一次占有兩只筷子在吃面，然后釋放所有資源；要么不占用資源。這樣就不會(huì)導(dǎo)致死鎖了。五、具體實(shí)現(xiàn)5.1、流程圖（參考）5.2、添加函數(shù)的代碼(所用到的各子函數(shù))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a(bǔ)tfor%dsecondsnz/,argi,argi+EATTIME);sleep(argi+EATTIME);voidtest(intargi,char*state,intsemid)if(stateargi=HUNGRY&stateLEFTI=EATING&stateRIGHTEATING)stateargiSEATING;printf(/zHehe,philosopher#%dcan已a(bǔ)tnown，/,argi);v_operate(semid,argi);)else辻(stateargi!二HU

6、NGRY)printf(zzFaint,philosopher#%ddontwantto已a(bǔ)tnz，,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a(bǔ)t.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、修改原有函數(shù)部分代碼(頭文件變量定義主程序)#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:/*設(shè)置信號(hào)量數(shù)組初值*/arglarray二array;辻(semct1(semid,PhNum+1,SETALL,argl)=l)/*設(shè)置各信號(hào)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)/*將共享內(nèi)存映射到當(dāng)前進(jìn)程地址空間*/semct1(semid,0,IPC_RMID,argl);shmct1(shmid,IPC_RMID,&arg2);perror(Shmaterror!);exit(l);)for(fori=0;foriPhNum;fori+)stateforiTHINKING;/*初始化狀態(tài)數(shù)組*/signal(SIGINT,SIG_IGN);/*將進(jìn)程對(duì)中斷信號(hào)的處理設(shè)為忽略*/for(fori=l;fori=PhNum;fori+)/*創(chuàng)建5個(gè)哲學(xué)家子進(jìn)程*/wh訂e(fork

12、i=fork0)=1);辻(!forki)/*子進(jìn)程執(zhí)行代碼*/mynum=foril;signal(SIGINT,SIG.DFL);/*設(shè)置子進(jìn)程對(duì)SIGINT信號(hào)的處理過(guò)程*/-4-4break;辻(forki)vdiile(wait(char*)0)!=1);/*等待子進(jìn)程執(zhí)行結(jié)束，此處的(char*)0相當(dāng)于NULL,即忽略返回狀態(tài)*/semct1(semid,0,IPC_RMID,argl);shmdt(state);shmct1(shndd,IPC_RMID,&arg2);printf(z/nTmmonitor.Allisovern);)elsephilosopher(mynum,

13、state,semid);/*子進(jìn)程調(diào)用*/六、調(diào)試運(yùn)行結(jié)果唾)厲&創(chuàng)盟11月21日星期一10:21UfQmuyeTOQmuyemuye-laptop:文件(F)=6(V)終床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譏osopher#4,1willeatfor7secondsjPhilosopher2eatO.K.Canhisneighbourseat.Hehe.philosopher#1caneatnowOh,philosopher#3canteatnow!Imphilosopher#2,1willthinkfor6secondsll*mphilosopher#1,1willeatfor4seconds(PhilosopherMishungry