管程的實(shí)現(xiàn)主要內(nèi)容一、Hoare管程數(shù)據(jù)結(jié)構(gòu)二、Hoare的wait操作三、Hoare的signal操作四、管程的應(yīng)用一、Hoare管程數(shù)據(jù)結(jié)構(gòu)霍爾方法采用信號(hào)量實(shí)現(xiàn)條件變量，將信號(hào)量的PV操作和同步操作封裝在管程的過(guò)程中。Hoare管程數(shù)據(jù)結(jié)構(gòu)（1）mutex（2）next和next-count（3）x-sem和x-count（1）mutex信號(hào)量mutex管理管程入口處的等待隊(duì)列，供管程中過(guò)程互斥調(diào)用，初值為1。進(jìn)程調(diào)用管程中的任何過(guò)程時(shí)，應(yīng)執(zhí)行P(mutex)；進(jìn)程退出管程時(shí)應(yīng)執(zhí)行V(mutex)開(kāi)放管程，以便其它調(diào)用者進(jìn)入。進(jìn)程在等待資源期間，應(yīng)允許其它進(jìn)程進(jìn)入管程，故在wait操作中也必須執(zhí)行V(mutex)，否則會(huì)妨礙其它進(jìn)程進(jìn)入管程，導(dǎo)致無(wú)法釋放資源。123（2）next和next-count信號(hào)量next管理管程內(nèi)的緊急等待隊(duì)列，初值為0。凡發(fā)出signal操作的進(jìn)程應(yīng)該用P(next)掛起自己，加入緊急等待隊(duì)列，直到被釋放進(jìn)程退出管程或產(chǎn)生其它等待條件。進(jìn)程在退出管程的過(guò)程前，須檢查是否有別的進(jìn)程在信號(hào)量next（即緊急等待隊(duì)列）上等待，若有，則用V(next)喚醒它。next-count初值為0，用來(lái)記錄在next（即緊急等待隊(duì)列）上等待的進(jìn)程數(shù)目。12（3）x-sem和x-count信號(hào)量x-sem用來(lái)管理資源等待隊(duì)列，初值為0。進(jìn)程申請(qǐng)資源得不到滿足時(shí)，執(zhí)行P(x-sem)掛起，加入x-sem所代表的資源隊(duì)列。釋放資源時(shí)，需要知道是否有別的進(jìn)程在等待資源，因此用計(jì)數(shù)器x-count（初值為0）記錄等待資源（即資源等待隊(duì)列中）的進(jìn)程數(shù)。執(zhí)行signal操作時(shí)，應(yīng)使等待資源（即資源等待隊(duì)列中）的某個(gè)進(jìn)程立即恢復(fù)運(yùn)行，而不使其它進(jìn)程搶先進(jìn)入管程，這可以用V(x-sem)來(lái)實(shí)現(xiàn)。12每個(gè)管程定義如下數(shù)據(jù)結(jié)構(gòu)：typedefstructInterfaceModule{semaphoremutex;semaphorenext;intnext_count;}InterfaceModule;//進(jìn)程調(diào)用管程過(guò)程前使用的互斥信號(hào)量//發(fā)出signal的進(jìn)程掛起自己的信號(hào)量//在next上等待的進(jìn)程數(shù)//InterfaceModule是結(jié)構(gòu)體的名字mutex=1;next=0;next_count=0;//初始化語(yǔ)句voidenter(InterfaceModule&IM){P(IM.mutex);}//優(yōu)先喚醒管程內(nèi)緊急等待隊(duì)列中的等待進(jìn)程//當(dāng)管程內(nèi)無(wú)等待進(jìn)程時(shí)再喚醒管程外入口處的等待進(jìn)程voidleave(InterfaceModule&IM){if(IM.next_count>0)V(IM.next);elseV(IM.mutex);}二、Hoare的wait操作voidwait(semaphore&x_sem,int&x_count,InterfaceModule&IM){ x_count++; ifIM.next_count>0V(IM.next); elseV(IM.mutex);P(x_sem);x_count--;}//等待資源的進(jìn)程睡眠之前，優(yōu)先喚醒管程內(nèi)緊急等待隊(duì)列中的就緒進(jìn)程//若管程內(nèi)緊急等待隊(duì)列空，則喚醒管程入口處等待進(jìn)入管程的隊(duì)列中的進(jìn)程//喚醒其它進(jìn)程之后，等待資源的進(jìn)程加入x_sem所管理的資源等待隊(duì)列睡眠，下面的x_count--會(huì)暫停執(zhí)行，待該進(jìn)程被喚醒后再執(zhí)行//等待資源的進(jìn)程數(shù)增1，等待資源的進(jìn)程將加入x_sem所管理的資源等待隊(duì)列wait過(guò)程的一個(gè)執(zhí)行場(chǎng)景進(jìn)程P1在管程內(nèi)處于運(yùn)行狀態(tài)進(jìn)程P2在緊急等待隊(duì)列就緒進(jìn)程P3在管程入口處等待進(jìn)入管程現(xiàn)在P1調(diào)用wait過(guò)程初始狀態(tài)操作根據(jù)wait過(guò)程的操作定義，P1將停止運(yùn)行，進(jìn)入資源等待隊(duì)列。在此之前，P1必須首先喚醒P2，然后P1等待，P2運(yùn)行，P3繼續(xù)等待。wait過(guò)程細(xì)節(jié)P3入口等待隊(duì)列x1-sem資源等待隊(duì)列xn-sem資源等待隊(duì)列next-count緊急等待隊(duì)列管程入口等待隊(duì)列長(zhǎng)度next-count=1等待隊(duì)列長(zhǎng)度xn-count等待隊(duì)列長(zhǎng)度x1-count=管程管程等待區(qū)域…（即將進(jìn)入x1-sem資源等待隊(duì)列）x1_count++;ifIM.next_count>0P(x1_sem);V(IM.next);1P2P1P3入口等待隊(duì)列x1-sem資源等待隊(duì)列xn-sem資源等待隊(duì)列next-count緊急等待隊(duì)列管程入口等待隊(duì)列長(zhǎng)度next-count=1等待隊(duì)列長(zhǎng)度xn-count等待隊(duì)列長(zhǎng)度x1-count=管程管程等待區(qū)域…1P2P1（運(yùn)行）三、Hoare的signal操作voidsignal(semaphore&x_sem,int&x_count,InterfaceModule&IM){ ifx_count>0{ IM.next_count++; V(x_sem); P(IM.next); IM.next_count--;}}/*緊急等待隊(duì)列中的進(jìn)程數(shù)減少1個(gè)*///執(zhí)行signal操作的進(jìn)程將加入緊急等待隊(duì)列，因此該隊(duì)列進(jìn)程數(shù)增1//執(zhí)行signal操作的進(jìn)程自己阻塞前，先釋放一個(gè)等待資源的進(jìn)程//執(zhí)行signal操作的進(jìn)程進(jìn)入管程內(nèi)緊急等待隊(duì)列，下面的IM.next_count--暫停執(zhí)行，只有進(jìn)程被喚醒后才會(huì)執(zhí)行//若有等待資源的進(jìn)程，即x_sem資源等待隊(duì)列若有進(jìn)程P3入口等待隊(duì)列x1-sem資源等待隊(duì)列xn-sem資源等待隊(duì)列next-count緊急等待隊(duì)列管程入口等待隊(duì)列長(zhǎng)度next-count=等待隊(duì)列長(zhǎng)度xn-count等待隊(duì)列長(zhǎng)度x1-count=管程管程等待區(qū)域…1P2P1（P2即將喚醒管程內(nèi)的進(jìn)程P1）ifx1_count>0{IM.next_count++;P(IM.next);V(x1_sem);1P3入口等待隊(duì)列x1-sem資源等待隊(duì)列xn-sem資源等待隊(duì)列next-count緊急等待隊(duì)列管程入口等待隊(duì)列長(zhǎng)度next-count=等待隊(duì)列長(zhǎng)度xn-count等待隊(duì)列長(zhǎng)度x1-count=管程管程等待區(qū)域…1P2P1（P1運(yùn)行）x_count--;10P3入口等待隊(duì)列x1-sem資源等待隊(duì)列xn-sem資源等待隊(duì)列next-count緊急等待隊(duì)列管程入口等待隊(duì)列長(zhǎng)度next-count=等待隊(duì)列長(zhǎng)度xn-count等待隊(duì)列長(zhǎng)度x1-count=0管程管程等待區(qū)域…P2P1（P1運(yùn)行）1四、管程的應(yīng)用管程解決生產(chǎn)者-消費(fèi)者問(wèn)題typeproducer_consumer=monitor //管程定義{itemB[k]; //緩沖區(qū)個(gè)數(shù)intin,out; //存取指針intcount; //緩沖中產(chǎn)品數(shù)semaphorenotfull,notempty;//條件變量intnotfull_count,notempty_count;InterfaceModuleIM;defineappend,take;useenter,leave,wait,signal；//變量初始化In=out=0; count=0; notfull=0;notempty=0;notfull_count=notempty_count=0;IM.mutex=1;IM.next=0;IM.next_count=0;voidappend(itemx){ enter(IM); if(count==k)wait(notfull,notfull_count,IM); //緩沖已滿，在notfull隊(duì)列等待空白緩沖區(qū) B[in]=x; in=(in+1)%k; count++; //增加一個(gè)產(chǎn)品 signal(notempty,notempty_count,IM);//喚醒notempty隊(duì)列中的等待消費(fèi)者，自己入緊急等待隊(duì)列 leave(IM);}voidtake(item&x){ enter(IM);if(count==0)wait(notempty,notempty_count,IM);//在notempty隊(duì)列中等待滿緩沖區(qū) x=B[out]; out=(out+1)%k; count--; //減少一個(gè)產(chǎn)品 signal(notfull,notfull_count,IM);//喚醒notfull隊(duì)列中的等