Chapter 5

Question 1

what is a cooperating process

Answer 1

it can affect or be affected by other processes executing in the system

Question 2

define race condition

Answer 2

several processes access and manipulate the same data concurrency and the outcome of the execution depends on the particular order in which the action takes place

Question 3

what is a way to prevent race condition

Answer 3

process to be synchronized

Question 4

a solution to the critical-section must satisfy what 3 requirements

Answer 4

1. mutual exclusion
2. progress
3. bounded waiting

Question 5

define Peterson’s solution

Answer 5

restricted to two processes that alternate execution between their critical sections and remainder sections

Question 6

what should be used to see if a process is ready to enter its critical section

Answer 6

flag array

Question 7

define locking

Answer 7

protecting critical regions through the use of locks

Question 8

define mutex locks

Answer 8

mutual exclusion locks, simplest of synchronization tools, mutex lock has a boolean variable available whose value indicates if the lock is available or not

Question 9

atomic process when lock is available

Answer 9

call to acquire() lock before entering a critical section, release() lock when it exits the critical section

Question 10

define spinlock

Answer 10

the process spins while waiting for lock to become available, they are useful because context switch is not required

Question 11

define busy waiting

Answer 11

wastes CPU cycles that could’ve been put to use by other processes

Question 12

define semaphores

Answer 12

integer variable that is accessed through only 2 atomic operations: wait() and signal()

Question 13

define counting semaphores

Answer 13

unrestricted domain

Question 14

define binary semaphore

Answer 14

range between 0 and 1, behaves similarly to mutex locks

Question 15

expand on the use of semaphores to count instances

Answer 15

• goes up when releasing a resource signal()

- goes down when using resource wait()

Question 16

what keyword to synchronize semaphores

Answer 16

synch

Question 17

expand how semaphores work

Answer 17

when a process executes a wait() operation and finds a semaphore value is not positive, it must wait. but instead of busy waiting, process can block itself. block operation places a process into a waiting queue and state of process is switched to waiting state. then the control is transferred to CPU scheduler. the waiting state is then restarted by wakeup() operation and it goes to ready state

Question 18

define deadlocks

Answer 18

2 or more processes waiting indefinitely for an event that can be caused by only one of the waiting processes

Question 19

define starvation

Answer 19

also known as indefinite blocking, it is a situation in which processes wait indefinitely within the semaphore

Question 20

define priority inversion

Answer 20

scheduling problem when lower priority process holds a lock needed by higher priority process. solved by priority-inheritance protocol

Question 21

what is the dining philosophers problem

Answer 21

need to allocate several resources among several processes in a dead-lock free and starvation-free manner

Question 22

what is the difference between deadlocks and starvation

Answer 22

you can have starvation without deadlock.

Question 23

what is the type of error caused by using semaphores incorrectly

Answer 23

timing errors. need to do wait() and then signal(). no other combination of the methods work

Question 24

define monitor type

Answer 24

ADT, encapsulates data with a set of functions to operate on that data, includes a set of programmer-defined operations that are provided with mutual exclusion within the monitor

Question 25

how to invoke wait() operation of condition x

Answer 25

x.wait();

Question 26

what are the 2 processes that can continue execution in monitor usage

Answer 26

1. signal and wait

2. signal and continue