1
GATE CSE 2021 Set 1
MCQ (More than One Correct Answer)
+2
-0
Consider the following pseudocode, where S is a semaphore intialized to 5 in line#2 an counter is a shared variable intialized to 0 in line#1. Assume that the increment operation in line#7 is not atomic.
1. int counter = 0;
2. Semaphore S = init(5);
3. void parop(void)
4. {
5. wait (S);
6. wait (S);
7. counter++;
8. signal (S);
9. signal (S);
10. }
If five threads execute the function parop concurrently, which of the following program behavior (s) is/are possible?
2
GATE CSE 2019
MCQ (Single Correct Answer)
+2
-0.67
Consider the following snapshot of a system running $n$ concurrent processes. Process $i$ is holding $X_i$ instances of a resource $\mathrm{R}, 1 \leq i \leq n$. Assume that all instances of R are currently in use. Further, for all $i$, process $i$ can place a request for at most $Y_i$ additional instances of R while holding the $X_i$ instances it already has. Of the $n$ processes, there are exactly two processes $p$ and $q$ such that $Y_p=Y_q=0$. Which one of the following conditions guarantees that no other process apart from $p$ and $q$ can complete execution?
3
GATE CSE 2018
MCQ (Single Correct Answer)
+2
-0.6
In a system, there are three types of resources: $$E, F$$ and $$G.$$ Four processes $${P_0},$$ $${P_1},$$ $${P_2}$$ and $${P_3}$$ execute concurrently. At the outset, the processes have declared their maximum resource requirements using a matrix named Max as given below. For example, Max$$\left[ {{P_{2,}}F} \right]$$ is the maximum number of instances of $$F$$ that $${{P_{2,}}}$$ would require. The number of instances of the resources allocated to the various processes at any given state is given by a matrix named Allocation.
Consider a state of the system with the Allocation matrix as shown below, and in which $$3$$ instances of $$E$$ and $$3$$ instances of $$F$$ are the only resources available.
Allocation | |||
---|---|---|---|
E | F | G | |
P0 | 1 | 0 | 1 |
P1 | 1 | 1 | 2 |
P2 | 1 | 0 | 3 |
P3 | 2 | 0 | 0 |
Max | |||
---|---|---|---|
E | F | G | |
P0 | 4 | 3 | 1 |
P1 | 2 | 1 | 4 |
P2 | 1 | 3 | 3 |
P3 | 5 | 4 | 1 |
From the perspective of deadlock avoidance, which one of the following is true?
4
GATE CSE 2016 Set 2
Numerical
+2
-0
Consider a non-negative counting semaphore $$S.$$ The operation $$P(S)$$ decrements $$S,$$ and $$V(S)$$ increments $$S.$$ During an execution, $$20$$ $$P(S)$$ operations and $$12$$ $$V(S)$$ operations are issued in some order. The largest initial value of $$S$$ for which at least one $$P(S)$$ operation will remain blocked is _____________ .
Your input ____
Questions Asked from Deadlocks (Marks 2)
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