chapter 5 interprocess

Question 1

when correct execution depends on the timing of processes or threads running a critical section of code

Answer 1

Race condition

Question 2

when a lower priority item is unfairly delayed by higher priority items arriving later (never have chance to get into CPU)

Answer 2

Starvation

Question 3

a portion of a program that modifies a shared resources (where it will enter to do operation)

Answer 3

critical section

Question 4

the conditions where two or more processes are not able to continue because they are waiting on each other to either release a resource or do something

Answer 4

Deadlock

Question 5

Process executing concurrently in OS may be either ___________ or ____________ processes

Answer 5

independent or coorperating

Question 6

what is independent process

Answer 6

• If it cannot affect or be affected by the other process executing in the
  system
• If it does not share data with any other process

Question 7

what is cooperating process

Answer 7

 If it can affect or be affected by the other processes executing in the
system
 If it share data with any other process

Question 8

Several reasons for providing an environment that allows process cooperation (why process cooperation)?

Answer 8

• information sharing
• computation speedup
• modularity
• convenience

Question 9

cooperating process require __________ that will allow them to exchange _____ and ______

Answer 9

IPC (interprocess communication),
data and
information

Question 10

Two fundamental model of interprocess communication

Answer 10

• shared memory: faster
• message passing: time-consuming

Question 11

Other processes that wish to communicate using this ________must attach it to their _________

Answer 11

shared-memory segment,
address space

Question 12

The producer process produces ________ that is ________ by a consumer process

Answer 12

information
consumed

Question 13

what is unbounded buffer and bounded buffer?

Answer 13

unbounded buffer: not practical limit size on buffer
bounded buffer: there is a fixed size of buffer

Question 14

what is Message Passing system?

Answer 14

Mechanism for processes to communicate and to synchronize their actions

Question 15

IPC facility provides two operations

Answer 15

• send (message)
• receive (message)

Question 16

If processes P and Q wish to communicate, they need to via message passing systems

Answer 16

 Establish a communication link between them
 Exchange message via send/receive

Question 17

if processes wish to communicate via shared memory

Answer 17

IPC using shared memory requires communicating the process to establish a region of shared memory

Question 18

Implementation of communication link

Answer 18

Physical:
 Shared memory
 Hardware bus
 Network
Logical
 Direct or indirect
 Synchronous or asynchronous
 Automatic or explicit buffering

Question 19

Properties of direct communication link

Answer 19

 Link are established automatically
 A link is associated with exactly one pair of communicating processes
 Between each pair there exists exactly one link
 The link may be unidirectional, but is usually bi-directional

Question 20

what is direct communication

Answer 20

Processes must name each other explicitly
 send(P, message) – send a message to process P receive(Q, message) – receive a message from process Q

Question 21

what is indirect communication?

Answer 21

Messages are directed and received from mailboxes (also referred to as ports)
 Each mailbox has a unique id
 Processes can communicate only if they share a mailbox

Question 22

properties of communication link

Answer 22

Properties of the communication link
 Link established only if processes share a common mailbox
 A link may be associated with many processes
 Each pair of processes may share several communication links
 Link may be unidirectional or bi-directional

Question 23

Message passing may be either _______or _________

Answer 23

blocking or non-blocking

Question 24

what is synchronous

Answer 24

Blocking is considered synchronous
 Blocking send – the sender is blocked until the message is received
 Blocking receive – the receiver is blocked until a message is available

Question 25

what is asynchronous

Answer 25

Non-blocking is considered asynchronous
 Non-blocking send – the sender sends the message and continue
 Non-blocking receive – the receiver receives:  A valid message, or
 Null message

Question 26

When both send() and receive() are blocking, we have a _________
between the sender and receiver

Answer 26

rendezvous

Question 27

If special care is not taken to correctly coordinate or synchronize access to shared resources, it can cause a number of problems:

Answer 27

 Starvation
 Deadlock
 Data Inconsistency
 Shred Buffer Problem

Question 28

A condition can occur when multiple processes or threads compete for access to a shred resource

Answer 28

starvation

Question 29

A condition can occur when two processes need multiple shared resources at the same time in order to continue

Answer 29

A deadlock

Question 30

When shared resources are modified at the same time by multiple resources, data errors or inconsistencies may occur

Answer 30

data inconsistency

Question 31

 Sections of a program that might cause these problems are called __________
 Failure to coordinate access to a critical section is called a _____________

Answer 31

critical sections
race condition