Chapter II Classic synchronous exercises

Catalog

One . Single topic selection （ common 10 topic ,83 branch ）

1. ( Single topic selection ) The following process states are in transition , Which one is incorrect （ ）.

2. ( Single topic selection ) The system has n（n＞2） A process , And the process scheduler is no longer executed , Which of the following is unlikely to happen ？（ ）

3. ( Single topic selection ) About process status , The following statement is true （ ）.

4. ( Single topic selection ) The operating system is based on （ ） To control and manage processes that execute concurrently .

5. ( Single topic selection ) In a single processor system , If they exist at the same time 10 A process , The processes in the ready queue can have at most （ ） individual .

6. ( Single topic selection ) There is a counting semaphore S:(1) If several processes are right S the 28 Time P Operation and 18 Time V After the operation , Semaphore S The value of is 0.(2) Suppose several processes are on semaphores S the 15 Time P Operation and 2 Time V operation . How many processes are waiting for semaphores at this time S Of the queue （ ）.

7. ( Single topic selection ) The following about PV The correct statement of operation is （ ）.I.PV An operation is a system call command II.PV Operation is a low-level process communication primitive III.PV An operation is a process that cannot be interrupted IV.PV Operation consists of two non interruptible processes

8. ( Single topic selection ) There are two concurrent processes P1 And processes P2, The shared initial value is 1 Of x,P1 Yes x Add l,P2 Yes x reduce 1. Add 1 Sum minus 1 The sequence of instructions for operation is as follows :// Add 1 operation load R1,x // take x To register R1 in inc R1store x,R1 // take R1 The content is stored in x// reduce 1 operation load R2,x // take x To register R2 in dec R1store x,R2 // take R2 The content is stored in x After the two operations are completed ,x Value （ ）.

9. ( Single topic selection ) stay 9 A producer ．6 The shared capacity of consumers is 8 The manufacturer of the buffer - Consumer problem , The initial value of semaphore of mutually exclusive buffer is （ ）.

10. ( Single topic selection ) Set the semaphore associated with a resource （K） The initial value is 3, The current value is 1. if M Indicates the number of available resources ,N Indicates the number of processes waiting for the resource , be M,N Namely （ ）.

Two . Other （ common 2 topic ,17 branch ）

11. ( Other ) A fast food restaurant has 4 Class Employee ：( l ） Foreman ： Accept customers' orders ;( 2 ） The cook ： Prepare customers' meals ;( 3 ) Contractor ： Pack the prepared food ;( 4 ） cashier ： Collect and submit food . Each employee can be regarded as a process , Try a synchronization mechanism to write programs that can make four types of employees run correctly and concurrently .

***：8.3 branch

12. ( Other ) A bank provides 1 A service window and 10 A seat for customers to wait . When the customer arrives at the bank , If a seat is available , Then go to the number taking machine to get a number , Wait for the call . Only one customer is allowed to use the number picking machine at a time . When the salesperson is free , Select a customer by calling , And serve them . The activity process of customers and salespeople is described as follows ：cobegin{ process customer i{ Get a number from the number machine ; Wait for the call ; Get services ;}process Sales Clerk { while(TRUE){ Call ; Serving customers ; } }}coend Please add the necessary semaphores and P、V( or wait（）、signal（）) operation , Realize mutual exclusion and synchronization in the above process . Ask to write a complete process , Explain the meaning of semaphore and assign initial value .

***：8.7 branch

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One . Single topic selection （ common 10 topic ,83 branch ）

1. ( Single topic selection ) The following process states are in transition , Which one is incorrect （ ）.

• A. be ready → Blocking

• B. function → be ready

• C. be ready → function

• D. Blocking → be ready

My answer : A right key : A

8.3 branch

Analysis of the answer ： Ready state means that everything is ready , Only owe CPU The state of , As long as it is not running , It will not become a state other than ready .

2. ( Single topic selection ) The system has n（n＞2） A process , And the process scheduler is no longer executed , Which of the following is unlikely to happen ？（ ）

• A. There is a running process , There is no ready process ,n-1 A blocking process .

• B. There is a running process , There is a ready process ,n-2 A blocking process .

• C. There is a running process ,n-1 A ready process , There is no blocking process .

• D. There is no running process , Yes 2 A ready process ,n-2 A blocking process .

My answer : D right key : D

8.3 branch

Analysis of the answer ：

D In the options , There is a ready process ,CPU Once you're free , The system will select a ready process to execute , So it is impossible to have a ready process without a running process .

3. ( Single topic selection ) About process status , The following statement is true （ ）.

• A. Once the process is formed , The first thing to enter is the running state .

• B. A process must go through the three basic states of the process before it can end .

• C. A process may be in some basic state at the same time .

• D. In a time-sharing system , The time slice of a running process has expired and the process has not finished running , The process will go to the ready state .

My answer : D right key : D

8.3 branch

4. ( Single topic selection ) The operating system is based on （ ） To control and manage processes that execute concurrently .

• A. Basic state of the process

• B. Process control block

• C. Multiprogramming

• D. Priority of the process

My answer : B right key : B

8.3 branch

5. ( Single topic selection ) In a single processor system , If they exist at the same time 10 A process , The processes in the ready queue can have at most （ ） individual .

• A. 1

• B. 8

• C. 9

• D. 10

My answer : C right key : C

8.3 branch

6. ( Single topic selection ) There is a counting semaphore S:(1) If several processes are right S the 28 Time P Operation and 18 Time V After the operation , Semaphore S The value of is 0.(2) Suppose several processes are on semaphores S the 15 Time P Operation and 2 Time V operation . How many processes are waiting for semaphores at this time S Of the queue （ ）.

• A. 2

• B. 3

• C. 5

• D. 7

My answer : B right key : B

8.3 branch

Analysis of the answer ：

7. ( Single topic selection ) The following about PV The correct statement of operation is （ ）.I.PV An operation is a system call command II.PV Operation is a low-level process communication primitive III.PV An operation is a process that cannot be interrupted IV.PV Operation consists of two non interruptible processes

• A. I、III

• B. II、IV

• C. I、II、IV

• D. I、IV

My answer : C right key : B

0 branch

Analysis of the answer ：

8. ( Single topic selection ) There are two concurrent processes P1 And processes P2, The shared initial value is 1 Of x,P1 Yes x Add l,P2 Yes x reduce 1. Add 1 Sum minus 1 The sequence of instructions for operation is as follows :// Add 1 operation load R1,x // take x To register R1 in inc R1store x,R1 // take R1 The content is stored in x// reduce 1 operation load R2,x // take x To register R2 in dec R1store x,R2 // take R2 The content is stored in x After the two operations are completed ,x Value （ ）.

• A. May be -1 or 3

• B. Only for 1

• C. May be 0,1 or 2

• D. May be -1,0,1 or 2

My answer : C right key : C

8.3 branch

Analysis of the answer ：

9. ( Single topic selection ) stay 9 A producer ．6 The shared capacity of consumers is 8 The manufacturer of the buffer - Consumer problem , The initial value of semaphore of mutually exclusive buffer is （ ）.

• A. 1

• B. 6

• C. 8

• D. 9

My answer : A right key : A

8.3 branch

10. ( Single topic selection ) Set the semaphore associated with a resource （K） The initial value is 3, The current value is 1. if M Indicates the number of available resources ,N Indicates the number of processes waiting for the resource , be M,N Namely （ ）.

• A. 0,1

• B. 1,0

• C. 1,2

• D. 2,0

My answer : B right key : B

8.3 branch

Two . Other （ common 2 topic ,17 branch ）

11. ( Other ) A fast food restaurant has 4 Class Employee ：( l ） Foreman ： Accept customers' orders ;( 2 ） The cook ： Prepare customers' meals ;( 3 ) Contractor ： Pack the prepared food ;( 4 ） cashier ： Collect and submit food . Each employee can be regarded as a process , Try a synchronization mechanism to write programs that can make four types of employees run correctly and concurrently .

• My answer ：**0 branch

  

• right key ：

  semaphore S1 , S2 ,S3 , S4 ; S1 = 1 ;S2 =S3 = S4 = 0 ; cobegin {P1() { while(1) { There are customers coming ; wait( S1 ); Accept customers' orders ; signal( S2 ); } }P2 () { while(1){ wait(S2 ) ; Prepare customers' meals ;signal( S3 ) ; } }P3() { while(1){ wait(S3 ) ; Pack the prepared food ;signal( S4 ) ; }} P4 () { while(1){ wait( S4 ) ; Collect and submit food ;signal( S1 ) ; } }} coend

***：8.3 branch

12. ( Other ) A bank provides 1 A service window and 10 A seat for customers to wait . When the customer arrives at the bank , If a seat is available , Then go to the number taking machine to get a number , Wait for the call . Only one customer is allowed to use the number picking machine at a time . When the salesperson is free , Select a customer by calling , And serve them . The activity process of customers and salespeople is described as follows ：cobegin{ process customer i{ Get a number from the number machine ; Wait for the call ; Get services ;}process Sales Clerk { while(TRUE){ Call ; Serving customers ; } }}coend Please add the necessary semaphores and P、V( or wait（）、signal（）) operation , Realize mutual exclusion and synchronization in the above process . Ask to write a complete process , Explain the meaning of semaphore and assign initial value .

• My answer ：**0 branch

  

• right key ：

  semaphore enmpty=10,// Empty seats mutex=1,// Sign taking is mutually exclusive full=0,// Number of customers waiting service=0;// Wait for the call cobegin{ process customer i { P(empty);//wait(empty) P(mutex);//wait(mutex) Get a number from the number machine ; V(mutex);//signal(mutex); V(full);//signal(full) P(service);//wait(service) Wait for the call Get services ;}process Sales Clerk { while(TRUE){ P(full);//wait(full) V(empty);//signal(empty) V(service)//signal(service), Call Serving customers ; } }}coend

Analysis of the answer ：

***：8.7 branch