Ch. 5 PPT

Question 1

What is OS design concerned with in terms of multiple processes?

Answer 1

The management of processes and threads

Question 2

What is multiple applications?

Answer 2

Processing time is shared among active applications

Question 3

What are structured applications?

Answer 3

An extension of modular design and structured programming

Question 4

What is operating system structure?

Answer 4

The OS implemented as a set of processes and threads

Question 5

What are interleaving and overlapping?

Answer 5

Concurrent processing

Question 6

What is uniprocessor?

Answer 6

The relative speed of execution of processes cannot be predicted

Question 7

What makes concurrency difficult?

Answer 7

Sharing/allocating resources, programming errors

Question 8

What is a race condition?

Answer 8

When multiple threads are reading and writing data items

Question 9

How should the OS deal with concurrency?

Answer 9

Try to allocate/deallocate resources, protect against race conditions

Question 10

What is resource competition?

Answer 10

When concurrent processes are fighting over same resource, such as IO devices and memory and such

Question 11

What is a critical resource?

Answer 11

One that is non-sharable. Used by a critical section of a process

Question 12

What is deadlock?

Answer 12

Concurrent programs are completing for a critical resource that one might need at the same time as another resource

Question 13

What is starvation?

Answer 13

When things need periodic access to the same resource

Question 14

What is mutual exclusion?

Answer 14

When a process halts, it cannot interfere with other processes. No deadlock, and no denial to critical resources that are not in use

Question 15

How can you guarantee mutual exclusion in a hardware level?

Answer 15

Disable interrupts. Does not work in multiprocessor environments. Lower efficiency

Question 16

How can the ISA enable mutual exclusion?

Answer 16

Including a compare/swap. Instructions are swapped if the memory address and the instruction are the same

Question 17

What is busy waiting?

Answer 17

When a process executes something else while it waits to go into a critical section

Question 18

What is an atomic instruction?

Answer 18

One that is non-interruptable

Question 19

What is bad about special instructions?

Answer 19

Starvation and deadlock are possible, and processor time is used due to busy waiting

Question 20

What is a semaphore?

Answer 20

An integer used for signaling among processes

Question 21

What does semWait do?

Answer 21

Decrement the value

Question 22

What does semSignal do?

Answer 22

Increment the value

Question 23

What is a strong semaphore?

Answer 23

The process that has been blocked the longest is released from the queue first (FIFO)

Question 24

What is a weak semaphore?

Answer 24

The order in which processes are removed from a queue is not specified

Question 25

What are drawbacks of semaphores?

Answer 25

There is no way to know if a process will be blocked when it decrements, no way to know which process will continue to run, and if the number of unblocked processes is zero or one

Question 26

What is producer/consumer?

Answer 26

The issue I was running into with the queue forwarder

Question 27

What is monitoring?

Answer 27

An easier implementation to semaphores. Operated with a single wait/signal function

Question 28

What is message synchronization for?

Answer 28

Enforcing mutual exclusion

Question 29

What is message communication for?

Answer 29

Exchanging information

Question 30

How does message passing do blocks?

Answer 30

If there is no message received, the process is blocked until one is received

Question 31

What is a rendezvous?

Answer 31

When both the sender and receiver are blocked until the message is delivered

Question 32

What is direct messaging?

Answer 32

There is a specific identifier of the destination process

Question 33

What is indirect messaging?

Answer 33

Messages are sent to a shared queue data structure