Ch. 6 PPT

Question 1

What is deadlock?

Answer 1

The permanent blocking of a set of processes that either compete for system resources or communicate with each other

Question 2

How can you tell if something is deadlocked?

Answer 2

If each element of a set is waiting an event by another element that is also blocked

Question 3

What is hold and wait?

Answer 3

A process may hold allocated resources while awaiting assignment of others

Question 4

What is no pre-emption?

Answer 4

No resource can be forcibly removed from a process holding it

Question 5

What is circular wait?

Answer 5

A closed chain of processes exists, such that each process holds at least one resource needed by the next process in the chain

Question 6

What is deadlock prevention?

Answer 6

Attempting to design a system such that deadlock is excluded

Question 7

How is deadlock prevention approached?

Answer 7

Indirect: Prevent the three necessary conditions. Direct: precent circular wait

Question 8

What is no preemption?

Answer 8

If a process is denied a further request, it must release its currently held resources.

Question 9

How can a deadlock be avoided?

Answer 9

By determining if a request can lead to a future deadlock. Requires knowing future requests

Question 10

What is another way of preventing deadlock?

Answer 10

By imposing resource restrictions on processes

Question 11

How does deadlock detection work?

Answer 11

It gives the process whatever it asks for

Question 12

What is good about deadlock detection?

Answer 12

The algorithm is simple and it can lead to early detection

Question 13

What is bad about deadlock detection?

Answer 13

It consumes more processor time

Question 14

What is a deadlock recovery strategy?

Answer 14

Abort all deadlocked processes, or abort some until the deadlock is gone, or restore to a pre-deadlock time

Question 15

What is the dining philosopher problem?

Answer 15

Encore mutual exclusion.. No two things can use the same resource at the same time

Question 16

What is a pipe?

Answer 16

A unix construct that allows for two processes to communicate in the producer-consumer model

Question 17

What is a message?

Answer 17

A unix construct with system calls and accompanying types for a message and mailboxes

Question 18

What is shared memory?

Answer 18

A block of virtual memory shared by processes. The fastest form of communication. Needs outside enforcement of mutual exclusion

Question 19

What is a signal?

Answer 19

A software element that informs a process of asynchronous events occurring. Similar to hardware interrupt

Question 20

How does a process respond to a signal?

Answer 20

Preforming a default action, executing a signal handler function, or ignoring the signal

Question 21

What is a bitmap operation?

Answer 21

An atomic operation that operates on an arbitrary memory location

Question 22

What is an integer operation?

Answer 22

An atomic operation that operates on an integer, typically in a counter

Question 23

What is a spin lock?

Answer 23

A method of protecting a critical section in linux. It can only be acquired by one thread at a time

Question 24

How does linux handle semaphores?

Answer 24

They are implemented in the kernel and are more powerful than user-level semaphores

Question 25

What is a mutual exclusion lock? (MUTEX)

Answer 25

Only one thread at a time can access a protected resource. Implemented as a spin lock

Question 26

What is a condition variable?

Answer 26

Used to wait until a particular condition is true. must be used with a mutex