Question

QUESTION 1

Process P1 waits on the condition x in the monitor M. Process P2 calls x.signal() within a function defined in the same monitor M. What further scenario is possible? (Check all that apply.)

		Process P2 is suspended. Process P1 resumes the execution.
		Process P1 resumes the execution. Process P2 continues the execution.
		Process P2 continues the execution. Process P1 is nonetheless suspended until P2 leaves the monitor.
		The operation x.signal() fails.

QUESTION 2

The following pseudocode fragment adds an item to the tail of a doubly linked list that is shared among multiple processes. Which statement(s) is/are true about this fragment? (May have multiple answers)

/*1*/
/*2*/ item.prev = tail;
/*3*/ tail.next = item;
/*4*/ tail = item;
/*5*/

		This pseudocode does not represent a critical section.
		This pseudocode represents a critical section. An entry section shall be added on the line 1 and an exit section shall be added on the line 5.
		The pseudocode represents a critical section. Keyword monitor and an opening brace { shall be added on the line 1, and a closing brace } shall be added on the line 5.
		This pseudocode represents a critical section. Statements P(S) and V(S) shall be added on the lines 1 and 5, respectively.

QUESTION 3

Let S is a semaphore and C is a condition in a monitor. Which statement is true about the semantics of the operations S.signal() (same as S.unlock() or V(S)) and C.signal()?

		S.signal() may change the state of the semaphore, but C.signal() never changes the state of the condition.
		S.signal() is a blocking operation, but C.signal() is not.
		S.signal() unblocks all processes waiting on S, but C.signal() unblocks at most one process waiting on C.
		There is no difference between them: both allow a blocked process resume the execution.

Answer 1

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1) Process P2 continues the execution. Process P1 is nonetheless suspended until P2 leaves the monitor.

Process P2 is suspended. Process P1 resumes the execution.

2) This pseudocode represents a critical section. An entry section shall be added on the line 1 and an exit section shall be added on the line 5

This pseudocode represents a critical section. Statements P(S) and V(S) shall be added on the lines 1 and 5, respectively.

3) S.signal() may change the state of the semaphore, but C.signal() never changes the state of the condition.