Process Synchronization

Question 1

Processes can execute concurrently and may be interrupted at any time, partially completing execution

Answer 1

Process synchronization

Question 2

A solution to the Producer Consumer problem

Answer 2

Have a counter initially set to zero
counter++ whenever producer produces new buffer
counter- - whenever consumer consumes the buffer

Question 3

A scenario wherein there is data inconsistencies because of accessing the counter at the same time

Answer 3

Race condition

Question 4

A scenario wherein a process must ask permission to enter the critical section in ___, and may follow critical section with__, then ___

Answer 4

Critical section problem

Entry section, exit section, remainder section

Question 5

A solution to the critical section problem wherein if process p is executing in the critical section, no other processes can execute in their critical sections

Answer 5

Mutual exclusion

Question 6

A solution to critical section problem wherein if no process is in the critical section and a process wants to enter the critical section, then the selection of that process to enter cannot be postponed

Answer 6

Progress

Question 7

A solution to the critical section problem wherein a bound must exist on the number of times other processes can enter the critical section after a request has been made to enter the critical process and before the request is granted

Answer 7

bounded waiting

Question 8

A critical section handling approach wherein preemption is allowed when running inkernel mode

Answer 8

Preemptive approach

Question 9

A critical section handling approach wherein running is allowed until EXIT KERNEL MODE, BLOCK OR VOLUNTARILY YIELD CPU

• free of RACE CONDITIONS

Answer 9

Non-preemptive approach

Question 10

A two process solution which assumes that load and store are atomic and cannot be interrupted

What are the two variables used by this solution?

Answer 10

Peterson’s solution

int turn (indicated whose turn it is)
Boolean flag array (indicates if process is READY [true] to enter critical section)

Question 11

Hardware support for implementing critical section code via locks

Answer 11

Locking

Question 12

A processor that could disable interrupts

Answer 12

Uniprocessors

Question 13

Atomic / non-interruptable instruction wherein it is
-executed atomically
-returns ORIGINAL VALUE of passed parameter
-set new value of passed parameter to TRUE
SHARED BOOLEAN LOCK INITIALIZED TO FALSE

Answer 13

Test and set instruction

Question 14

Atomic/non-interruptable instruction wherein
-executed atomically
-return ORIGINAL VALUE of passed parameter
-if value == expected, value = new value (swap only if value is equa; to the expected)
SHARED LOCK INITIALIZED TO 0

Answer 14

Compare and swap instruction

Question 15

Simplest solution to critical section problem

System calls associated with this solution are?

Answer 15

Mutex locks

Acquire() , release()

Question 16

Since mutex locks require ___, this lock is called ___

Answer 16

Busy waiting, spinlock

Question 17

Synchronization tool that provides more sophisticated ways for process to synchronize their activities

What operations are associated with this?

Answer 17

Semaphore

Wait() , signal()

Question 18

A type of semaphore usage wherein int value can range over unrestricted domain

Answer 18

Counting semaphore

Question 19

Atype of semaphore usage wherein int value can range only between 0 and 1 which is the counterpart of mutex locks

Answer 19

Binary semaphore

Question 20

An implementation ofnthe semaphore wherein each semaphore has an assocated waiting queue

What are the data items in a waiting queue

Answer 20

Semaphore implementation without busy waiting

Value (int)
Pointer to next record on list

Question 21

An operation in semaphore w/ no busy waiting wherein you place the process invoking the operation on the appropriate waiting queue

Answer 21

Block

Question 22

An operation in semaphore w/ no busy waiting where you remove one process in the waiting queue and place it in the ready queue

Answer 22

Wakeup

Question 23

Two or more processes WAITING INDEFINITELY for an event caused by ONLY ONE of the waiting processes

Answer 23

Deadlock

Question 24

INDEFINITE BLOCKING wherein a process may NEVER BE REMOVED from the semaphore queue in which it is suspended

Answer 24

Starvation

Question 25

A scheduling problem where LOWER PRIORITY PROCESS holds a lock needed by a HIGHER PRIORITY PROCESS

What is a solution for this?

Answer 25

Priority inversion

Priority inheritance protocol

Question 26

High level abstraction that provides a convenient and effective mechanism for process synchronization

Answer 26

Monitor