Quiz #4

Question 1		Multiple Answer	(1 points)
	Question:	Which of the following statements is true about using special machine instructions (that perform a combination of fetching and storing to a memory location atomically) to achieve mutual exclusion?
		While a process is waiting for access to a critical section it continues to consume CPU time. It works for a SMP system. It can be used to support multiple critical sections; i.e., a process in one critical section will not block processes in other critical sections. Deadlock is possible. Starvation is possible. It is simple. The (maximum) number of processes that use the critical section must be known in advance.

Question 2 Multiple Answer (1 points)

Question: Which of the following statements is true about using interrupt disabling to achieve mutual exclusion?

While a process is waiting for access to a critical section is continues to consume CPU time.
It works for a SMP system.
It supports multiple critical sections; i.e., a process in one critical section will not block other processes in other critical sections.
Deadlock is possible.
Starvation is possible.
It is simple.
The (maximum) number of processes that use the critical section must be known in advance.

Question 3 Multiple Answer (1 points)

Question: Which of the following is true about the Dekker software algorithm to achieve mutual exclusion?

While a process is waiting for access to a critical section it continues to consume CPU time.
It is applicable between the processors of an SMP system.
It can be used to support multiple (independent) critical sections; i.e., a process in one critical section will not block processes in other critical sections.
Deadlock is possible.
Starvation is possible.
It is simple.
The (maximum) number of processes that use the critical section must be known in advance.

Question 4 Matching (1 points)

Question: Match the mutual exclusion mechanism with the hardware support for atomicity that it relies on.

Match Question Items

1. Dekker and Peterson software algorithms

2. Interrupt disabling

3. Test and Set and Exchange instruction solutions

Answer Items

A. atomic memory fetch and store operations

B. atomic pair of memory fetch and store operations

C. atomic sequence of CPU instructions

Question 5 Multiple Answer (1 points)

Question: Which are true of the (counting) semaphore operation Stallings calls "wait"?

it decrements the value of the semaphore
it increments the value of the semaphore
if the value becomes negative, the calling process is blocked
If the value is not positive, another process is unblocked
A lower-level mutual exclusion mechanism is needed, to ensure that the fetching and storing of the semaphore value are done atomically.

Question 6 Multiple Choice (1 points)

Question: A "weak" semaphore is one that

does not always achieve mutual exclusion
does not enforce FIFO ordering of unblocking
does not work for more than some fixed number of processes
supports a time-out if a process is blocked for too long

Question 7 Multiple Answer (1 points)

Question: Which of the following are true of the monitor concept?

a monitor enforces mutual exclusion around a set of data objects
a monitor may provide a set of condition variables, on which a process may wait
several processes may be executing inside a monitor at the same time
there are several variations on the monitor concept, which differ in details
a semaphore cannot be implemented as a monitor
POSIX mutexes and CVs are intended to implement monitors
monitors were introduced as a built-in programming language construct

Question 8 Multiple Answer (1 points)

Question: Which of the following are true of the pthread_mutex_lock() operation?

it takes a reference to a condition variable as a parameter
it takes a reference to a mutex as a parameter
it is intended to provide mutal exclusion
it is intended for waiting for a condition or event

Question 9 Multiple Answer (1 points)

Question: Which of the following is true of pthread_cond_wait()?

it takes a reference to a mutex as parameter
it takes a reference to a condition variable as parameter
it is intended to provide mutual exclusion
it unlocks a mutex
it is intended for waiting for a condition or event
a while-loop is required, to recheck what Stallings the logical condition"
it should only be called when the caller is holding the lock on a mutex
when it returns the caller is holding the lock on a mutex

Question 10 Multiple Answer (1 points)

Question: Which of the following is true of pthread_cond_signal()?

It matches the Hoare csignal more closely than the Lampson & Redell cnotify
at least one of the threads waiting on the CV will be unblocked
more than one thread waiting on the CV may be unblocked
if there is no thread waiting on the CV, the signal will be remembered, and the next thread to wait on the CV will not block
it takes a reference to a mutex as parameter
it takes a reference to a CV as parameter

Question 11 Multiple Choice (1 points)

Question: If process A is waiting for a nonpreemptible resource that is held by process B and process B is waiting for a nonpreemptable resource that is held by A, that is called:

starvation
livelock
deadlock
busy waiting
mutual exclusion
coroutine

Question 12 Multiple Choice (1 points)

Question: If processes A, B, and C are all requesting resource R, but the operating system allows A and B to access R repeatedly while C continues to wait for R, that is called:

starvation
livelock
deadlock
busy waiting
mutual exclusion
coroutine

Question 13 Multiple Choice (1 points)

Question: If a process must loop repeatedly, keeping the CPU occupied, to wait for a condition, that is called

starvation
livelock
deadlock
busy waiting
mutual exclusion
coroutine

Question 14 Multiple Choice (1 points)

Question: Stallings calls a timing-dependent situation, in which two or more processes continue trying to enter a critical section but none of them succeeds (even though there is no process in the critical section):

starvation
livelock
deadlock
mutual exclusion
busy waiting
coroutine

Question 15 True / False (1 points)

Question: The producer/consumer problem is a special case of the reader/writer problem, in which the producer is the writer and the consumer is the reader.

True
False

Question 16 True / False (1 points)

Question: In the readers/writers problem we want to allow multiple readers to be in their critical sections for the shared data at the same time.

True
False

Question 17 True / False (1 points)

Question: In the reader/writers problem we want to allow multiple writers to be in their critical sections for the shared data at the same time.

True
False

Question 18 True / False (1 points)

Question: In the readers/writers problem, we want to allow a reader and a writer to be in their critical sections for the shared data at the same time.

True
False

Question 19 True / False (1 points)

Question: If one thread of a process is holding the lock on a mutex, and another thread of the process attempts to lock the mutex, the whole process is blocked.

True
False

Question 20 True / False (1 points)

Question: In the producer/consumer problem the producer never has to wait.

True
False

Question 2		Multiple Answer	(1 points)
	Question:	Which of the following statements is true about using interrupt disabling to achieve mutual exclusion?
		While a process is waiting for access to a critical section is continues to consume CPU time. It works for a SMP system. It supports multiple critical sections; i.e., a process in one critical section will not block other processes in other critical sections. Deadlock is possible. Starvation is possible. It is simple. The (maximum) number of processes that use the critical section must be known in advance.

Question 3		Multiple Answer	(1 points)
	Question:	Which of the following is true about the Dekker software algorithm to achieve mutual exclusion?
		While a process is waiting for access to a critical section it continues to consume CPU time. It is applicable between the processors of an SMP system. It can be used to support multiple (independent) critical sections; i.e., a process in one critical section will not block processes in other critical sections. Deadlock is possible. Starvation is possible. It is simple. The (maximum) number of processes that use the critical section must be known in advance.

Question 5		Multiple Answer	(1 points)
	Question:	Which are true of the (counting) semaphore operation Stallings calls "wait"?
		it decrements the value of the semaphore it increments the value of the semaphore if the value becomes negative, the calling process is blocked If the value is not positive, another process is unblocked A lower-level mutual exclusion mechanism is needed, to ensure that the fetching and storing of the semaphore value are done atomically.

Question 6		Multiple Choice	(1 points)
	Question:	A "weak" semaphore is one that
		does not always achieve mutual exclusion does not enforce FIFO ordering of unblocking does not work for more than some fixed number of processes supports a time-out if a process is blocked for too long

Question 7		Multiple Answer	(1 points)
	Question:	Which of the following are true of the monitor concept?
		a monitor enforces mutual exclusion around a set of data objects a monitor may provide a set of condition variables, on which a process may wait several processes may be executing inside a monitor at the same time there are several variations on the monitor concept, which differ in details a semaphore cannot be implemented as a monitor POSIX mutexes and CVs are intended to implement monitors monitors were introduced as a built-in programming language construct

Question 8		Multiple Answer	(1 points)
	Question:	Which of the following are true of the pthread_mutex_lock() operation?
		it takes a reference to a condition variable as a parameter it takes a reference to a mutex as a parameter it is intended to provide mutal exclusion it is intended for waiting for a condition or event

Question 9		Multiple Answer	(1 points)
	Question:	Which of the following is true of pthread_cond_wait()?
		it takes a reference to a mutex as parameter it takes a reference to a condition variable as parameter it is intended to provide mutual exclusion it unlocks a mutex it is intended for waiting for a condition or event a while-loop is required, to recheck what Stallings the logical condition" it should only be called when the caller is holding the lock on a mutex when it returns the caller is holding the lock on a mutex

Question 10		Multiple Answer	(1 points)
	Question:	Which of the following is true of pthread_cond_signal()?
		It matches the Hoare csignal more closely than the Lampson & Redell cnotify at least one of the threads waiting on the CV will be unblocked more than one thread waiting on the CV may be unblocked if there is no thread waiting on the CV, the signal will be remembered, and the next thread to wait on the CV will not block it takes a reference to a mutex as parameter it takes a reference to a CV as parameter

Question 11		Multiple Choice	(1 points)
	Question:	If process A is waiting for a nonpreemptible resource that is held by process B and process B is waiting for a nonpreemptable resource that is held by A, that is called:
		starvation livelock deadlock busy waiting mutual exclusion coroutine

Question 12		Multiple Choice	(1 points)
	Question:	If processes A, B, and C are all requesting resource R, but the operating system allows A and B to access R repeatedly while C continues to wait for R, that is called:
		starvation livelock deadlock busy waiting mutual exclusion coroutine

Question 13		Multiple Choice	(1 points)
	Question:	If a process must loop repeatedly, keeping the CPU occupied, to wait for a condition, that is called
		starvation livelock deadlock busy waiting mutual exclusion coroutine

Question 14		Multiple Choice	(1 points)
	Question:	Stallings calls a timing-dependent situation, in which two or more processes continue trying to enter a critical section but none of them succeeds (even though there is no process in the critical section):
		starvation livelock deadlock mutual exclusion busy waiting coroutine

Question 15		True / False	(1 points)
	Question:	The producer/consumer problem is a special case of the reader/writer problem, in which the producer is the writer and the consumer is the reader.
		True False

Question 16		True / False	(1 points)
	Question:	In the readers/writers problem we want to allow multiple readers to be in their critical sections for the shared data at the same time.
		True False

Question 17		True / False	(1 points)
	Question:	In the reader/writers problem we want to allow multiple writers to be in their critical sections for the shared data at the same time.
		True False

Question 18		True / False	(1 points)
	Question:	In the readers/writers problem, we want to allow a reader and a writer to be in their critical sections for the shared data at the same time.
		True False

Question 19		True / False	(1 points)
	Question:	If one thread of a process is holding the lock on a mutex, and another thread of the process attempts to lock the mutex, the whole process is blocked.
		True False

Question 20		True / False	(1 points)
	Question:	In the producer/consumer problem the producer never has to wait.
		True False