Chapter 22

Question 1

What are semaphorse in operating system solutions

Answer 1

semaphorse is a synchronization tool. It is available in operating system. It is an integer variable that can only be accessed via two indivisible (atomic) operations, called wait and signal. example of a white road block in traffic signal. A car or a bus can cross it at a time.

Question 2

What are 2 operations used by semaphorse

Answer 2

1. Wait

2. Signal

Question 3

What wait operation do in semaphorse

Answer 3

It keeps waiting and wait for value of semaphorse that is less than equal to 0 to increase.

Question 4

What are 2 types of atomic execution

Answer 4

1. Uni-processor environment

2. Bus-based multi-process environment

Question 5

What is Uni-processor environment

Answer 5

We inhibit interrupts before executing code of wait() and signal()

Question 6

What is bus-based multi-processor environment

Answer 6

we use software solution in it (e.g. bakery algorithm). we lock the data bus

Question 7

What is busy waiting

Answer 7

processes keep waiting and in loop. Its a wastage of CPU resources.

Question 8

What are 2 simple operations in semaphore implementation

Answer 8

1. block() suspends the process that invoke it

2. wakeup() resume the execution of blocked process

Question 9

What is the meaning of negative value of a semaphore

Answer 9

The negative value of s value indicates the number of processes waiting for semaphore.

Question 10

How to stop busy waiting

Answer 10

We put semaphore queue so process spinning in a loop should be waiting in a queue.

Question 11

What is atomic operation

Answer 11

An operation that performs interrupted. e.g. 2 atomic operations can not take place at the same time on a semaphorse.