进程管理-基本概念

进程同进程同步的基本概 2.3进程同

VARtop:integer=-1stack:array[0..n-1]ofProgramAwhile(TRUEtop:=(top+1)mod stack[top]:=x endProgramBwhile(TRUEtop:=(top+1)mod stack[top]:=y endwhile 2.3进程同

VARtop:integer=-1ProgramAwhileProgramAwhile(TRUEtop:=(top+1)modstack[top]:=xend 如何实现临界资源的互

ProgramBwhile(TRUEtop:=(top+1)modstack[top]:=yendwhile201arend2.3进程同 临界资 互临界 互

VARtop:integer=-1stack:array[0..n-1]ofitem;ProgramA:while(TRUEtoptop:=(top+1)modn;stack[top]:=x;endwhileProgramB:while(TRUEtoptop:=(top+1)modn;stack[top]:=y;

end201arend2.3进程同criticalsectioncriticalsectionremaindersectionuntil

entrycriticalsection;exitsection;remaindersection;untilfalse空闲让进：当无进程处于临界区忙则等待：当已有进程进入临界有限等待：对要 临界资源进程，保证能在有限时间内进入临界让权等待：当进程不能进入临界区时，应释放处理机 2.3进程同

VARfree:boolean:=false实现进程同步的早期软件解法1资源空闲标志:free=false:Free=true:

Programwhile(while(free)free:=truefree:=falsefree:=falseuntilProgramwhile(while(free)free:=truefree:=falsefree:=false

remaindersectionuntilfalse82.3进程同

VARturn:integer:=12.3.2实现进程同步的早期

Programwhile(while(turn=2)turn:=2turn:=2remaindersectionuntil严格限制资 顺

Programwhile(while(turn=1)turn:=1turn:=1

remaindersectionuntilfalse92.3进程同

VARpturn,qturn:boolean:=false,false2.3.2实现进程同步的早期方Programpturn:=truepturn:=truewhile(qturn)

criticalsection;remaindersection;pturn:=falsepturn:=falseProgramqturnqturn:=truewhile(pturn)criticalsectionqturnqturn:=falseremaindersection;untilfalse

12.3进程同2.3.2实现进程同步的早期方#defineFALSE#define

Programenter_region(0enter_region(0criticalsection intint

进程的个 数组，初始值均为

remaindersectionuntilvoidenter_regionintprocessprocess0或{int //另外一个进程的进程other=1- interested[process]=TRUE表明本进程turn= 设置标志while(turn==process&&interested[other]==}voidleave_region(int{interested[process]= //本进程已离开

Programenter_region(1);criticalsection;remaindersection;untilfalseVARlock:boolean:=VARlock:boolean:=falseProgramcriticalsectionremaindersectionuntilfalseProgramcriticalsection;remaindersection;untilenter_region(lock2.3.2实现进程同步的早期方//交换锁lock//交换锁lock和key的functionSWAP(lock,key){vartmp:boolean:=lock;lock:=key;key:=tmp}functionfunctionenter_region(varlockbooleanVarkey:boolean;//局部变量key:=functionleave_region(varlock:booleanlock:=false;进程同实现进程同步的早期方 信号量机制的提出荷兰计算机科学家EdsgerWybeDijkstra; 第一个Algol60编译器的设计者 VARS:integer:=1VARS:integer:=1;ProgramP1:criticalsectionremaindersection;untilfalseProgramcriticalsectionremaindersectionuntil信号量机整数信号量S; P/VfunctionfunctionWait(varS:integerwhile(S<=0)dono_op();S:=S-1;functionSignal(varS:integer)S:=VARS:semaphore:=1;ProgramP1:VARS:semaphore:=1;ProgramP1:criticalsection;remaindersection;untilfalseProgramcriticalsection;remaindersection;untilwait(S两个原子操作 P/Vtypesemaphore=value:integerL:listofprocess

//阻塞进程队functionwait(varS：Semaphore)S.value:=S.value-if(S.value<0)thenblock(S.L);functionsignal(varS：SemaphoreS.value:=if(S.value<=0)thenwakeup(S.L);2.3进程同(2)资源，因此描述为S.value:=S.value-1；当S.value＜0时，表源，故S.value:=s.value+1操作表示资源数目加1。若加1后仍S.value:S.value>=0:资源数量；S.value<0: |S.value|合肥工业大学操作系统课程组 2.3进程同信号量的应例1：2

VARtop:integer=-1stack:array[0..n-1]ofmutex:semaphore:=1ProcessProcessP1while(TRUEtop:=(top+1)modstack[top]:=xendsignal(mutex)wait(mutex)ProcessProcessP2while(TRUEtop:=(top+1)modn;stack[top]:=y;endwhilesignal(mutex)wait(mutex)

2.3进程同(1)河河河河 ProcessN2SProcessN2Sgoacrossthebridgeuntilsignal(mutex)wait(mutex)ProcessS2Ngoacrossthebridge;untilfalsesignal(mutex)wait(mutex)VARmutex:semaphore=1ProcessN2Sgoacrossthebridge;untilfalseProcessS2Ngoacrossthebridge 2.3进程同(2)B VARS1,S2:VARS1,S2:semaphore=1,0ProcessPIreadxfromI/OB:=xuntilProcessPOy:=Bprint(y);untilfalsesignal(S1)wait(S2)signal(S2)wait(S1)ProcessPOy:=Bprint(y)untilProcessPIreadxfromI/O;B:=x;until组组 进程同(2)B3：IEBI负责产生随机数B中，当B中数据为奇数时由O负责打印，当B中数B ProcessProcessPEy:=Bprint(y);untilfalseProcessPOz:=Bprint(z);untilfalseProcessPIgeneratexB:=xuntilvarS,SO,SE:semaphoreProcessPEy:=B;signal(S);print(y);ProcessPOz:=Bsignal(S);print(z);untilProcessPIgeneratexB:=xif(xisodd)signal(SO); signal(SE)until组组 经典进程同步问生产者-消费者问循环缓冲

出队操 VARempty,full:semaphore:=n,0;in,out:integer:=0,0;Buffer:array[0..n-1]ofitemproduceaniteminnextp;wait(empty);Buffer(in):=nextp;in:=(in+1)modn;signal(full)untilwait(full)nextc=out:=(out+1)modn课程组课程组

signal(empty)consumetheitemnextc;untilflasein,out:integerin,out:integer:=0,0Buffer:array[0..n-1]ofitem produceaniteminnextpBuffer(in):=nextp;in:=(in+1)modn;untilnextc=out:=(out+1)modnconsumetheitemnextc;untilflase

VARmutex,VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0Buffer:array[0..n-1]ofitem;produceaniteminnextp;wait(empty);wait(mutex);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilwait(full);wait(mutex);nextc=out:=(out+1)modnsignal(mutex);signal(empty)consumetheitemnextc;untilflase (2)

合肥工业大学操作

VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(empty)wait(mutex);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(full)wait(mutex);nextc=Buffer(out);out:=(out+1)modnsignal(mutex);signal(empty)consumetheitemnextcuntilflase(2)

VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(empty)wait(mutex);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(full)wait(mutex)nextc=out:=(out+1)modnsignal(mutex);signal(empty)consumetheitemnextcuntil合肥工业大学操作

(2)

VARmutex,empty,full:semaphore:=1,n,0;in,out:integer:=0,0;Buffer:array[0..n-1]ofitemproduceaniteminnextp;wait(empty);Buffer(in):=nextp;in:=(in+1)modn;

signal(full)untilwait(full)nextc=out:=(out+1)modn合肥工业大学操作系统

signal(empty);consumetheitemnextc;程组 程组 (2)

同例VARempty,full:VARempty,full:semaphore:=1,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextp;wait(empty);Buffer(in):=nextp;in:=(in+1)modn;signal(full);untilwait(full)nextc=out:=(out+1)modn;signal(empty);consumetheitemnextc;until(2)

VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(empty)wait(mutex);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(full)wait(mutex);nextc=Buffer(out);out:=(out+1)modnsignal(mutex);signal(empty)consumetheitemnextc系统课程组 系统课程组 合肥工业大学操

(2)

VARmutexC,mutexP,empty,full:semaphore:=1,1,n,0;in,out:integer:=0,0;Buffer:array[0..n-1]ofitemproduceaniteminnextp;wait(empty);wait(mutexP);Buffer(in):=nextp;in:=(in+1)modn;signal(mutexP);signal(full);untilwait(full)wait(mutexC);nextc=Buffer(out);out:=(out+1)modnsignal(mutexC);signal(empty);consumetheitemnextc;操作系统课程组 操作系统课程组 合肥工业大

(2)

VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(empty)wait(mutex);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(full)wait(mutex);nextc=Buffer(out);out:=(out+1)modnsignal(mutex);signal(empty)consumetheitemnextc作系统课程组 作系统课程组 合肥工业大学

(2)

合肥工业大学

VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(mutex);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(full)wait(mutex);nextc=Buffer(out);out:=(out+1)modnsignal(mutex)consumetheitemnextc;untilflase作系统课程组作系统课程组 (2)

合肥工业大学

VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(mutex)wait(empty);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(full)wait(mutex);nextc=Buffer(out);out:=(out+1)modnsignal(mutex);signal(empty)consumetheitemnextcuntil作系统课程组作系统课程组 (2)

合肥工业大学

VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(empty)wait(mutex);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(mutex)wait(full)nextc=out:=(out+1)modnsignal(mutex)signal(empty);consumetheitemnextc;until作系统课程组作系统课程组 (2)

VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(mutex)wait(empty);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(mutex)wait(full)nextc=out:=(out+1)modnsignal(mutex);signal(empty)consumetheitemnextcuntil合肥工业大学4操作系统end组(2)VARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(empty);wait(mutex)Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(full)wait(mutex);nextc=Buffer(out);out:=(out+1)modnsignal(empty);signal(mutex)consumetheitemnextcuntil合肥工业大学4操作系统end组(2)

VARVARmutex,empty,full:semaphore:=1,n,0in,out:integer:=0,0;Buffer:array[0..n-1]ofitem;produceaniteminnextpwait(empty)wait(mutex);Buffer(in):=nextp;in:=(in+1)modn;signal(mutex);signal(full);untilflasewait(full)wait(mutex);nextc=Buffer(out);out:=(out+1)modnsignal(mutex);signal(empty)consumetheitemnextcuntil 合肥工业大学2.4经典进程同步问读者-写者问

读写读写 VARVARwmutex:semaphore:=1wait(wmutex);performreadoperation;signal(wmutex);untilflasewait(wmutex);performwriteoperation;signal(wmutex);untilflase VARVARwmutex:semaphore:=1readcount:integer:=0if(readcount=0)wait(wmutex);readcount:=readcount+1;performreadoperation;readcount:=readcount-1if(readcount=0)signal(wmutex);untilflasewait(wmutex);performwriteoperation;signal(wmutex);until

VARVARwmutex:semaphore:=1;readcount:integer:=0;if(readcount=0)wait(wmutex);readcount:=readcount+1;performreadoperation;readcount:=readcount-1if(readcount=0)signal(wmutex);untilflasewait(wmutex);performwriteoperation;signal(wmutex);untilVARrmutex,wmutex:semaphore:=1,1;readcount:integer:=0;wait(rmutex)VARrmutex,wmutex:semaphore:=1,1;readcount:integer:=0;wait(rmutex)if(readcount=0)wait(wmutex);readcount:=readcount+1;signal(rmutex);performreadoperationwait(rmutex)readcount:=readcount-1if(readcount=0)signal(wmutex)signal(rmutex)untilwait(wmutex);performwriteoperation;signal(wmutex);untilflase VARrmutex,wmutex:VARrmutex,wmutex:semaphore:=1,1readcount:integer:=0;wait(rmutex)if(readcount=0)wait(wmutex);readcount:=readcount+1;signal(rmutex);performreadoperationwait(rmutex)readcount:=readcount-1if(readcount=0)signal(wmutex)signal(rmutex)untilwait(wmutex);performwriteoperation;signal(wmutex);untilflase 2.4经典进程同步问哲学家进餐问 哲学家进程：互斥（筷子 VARVARchopsticks:array[0..4]ofsemaphore:=1,1,1,1,1wait(chopsticks[i])wait(chopsticks[(i+1)mod5]eatsignal(chopsticks[i])signal(chopsticks[(i+1)mod5]untilflase 0 2

VARVARchopsticks:array[0..4]ofsemaphore:=1,1,1,1,1philosopher0-wait(chopsticks[i])wait(chopsticks[(i+1)mod5]);eat;signal(chopsticks[i])signal(chopsticks[(i+1)mod5]untilflasewait(chopsticks[(i+1)mod5]wait(chopsticks[i]);eat;signal(chopsticks[i])signal(chopsticks[(i+1)mod5]untilflase4 0 2 经典进程同步问理发师问题(课后思考题(1) 2.4经典进程同步问信号量集机 2.4.5信号量集机typesemaphore=value:integerL:listofprocess;

//阻塞进程队functionSwait(varS1,S2,..,Sn：Semaphoreif(S1>=1and…andSn>=1)fori:=1tondoSi:=Si-1PlacetheprocessinthequeueassociatedwiththefirstSifoundwithSi<1,gotothebeginningoffunctionSsignal(varS1,S2,..,Sn：Semaphorefo