1
GATE CSE 2014 Set 2
MCQ (Single Correct Answer)
+2
-0.6
Consider the procedure below for the Producer-Consumer problem which uses semaphores:
semaphore n = 0;
semaphore s = 1;
void producer()
{
    while(true)
    {
     produce();
     semWait(s);
     addToBuffer();
     semSignal(s);
     semSignal(n);
    }
}
void consumer()
{
   while(true)
   {
    semWait(s);
    semWait(n);
    removeFromBuffer();
    semSignal(s);
    consume();
   }
}
Which one of the following is TRUE?
A
The producer will be able to add an item to the buffer, but the consumer can never consume it.
B
The consumer will remove no more than one item from the buffer.
C
Deadlock occurs if the consumer succeeds in acquiring semaphore s when the buffer is empty.
D
The starting value for the semaphore n must be 1 and not 0 for deadlock-free operation.
2
GATE CSE 2014 Set 1
MCQ (Single Correct Answer)
+2
-0.6
An operating system uses the Banker’s algorithm for deadlock avoidance when managing the allocation of three resource types X, Y, and Z to three processes P0, P1, and P2. The table given below presents the current system state. Here, the Allocation matrix shows the current number of resources of each type allocated to each process and the Max matrix shows the maximum number of resources of each type required by each process during its execution. GATE CSE 2014 Set 1 Operating Systems - Deadlocks Question 11 English There are 3 units of type X, 2 units of type Y and 2 units of type Z still available. The system is currently in a safe state. Consider the following independent requests for additional resources in the current state:

REQ1: P0 requests 0 units of X, 0 units of Y and 2 units of Z
REQ2: P1 requests 2 units of X, 0 units of Y and 0 units of Z

Which one of the following is TRUE?
A
Only REQ1 can be permitted.
B
Only REQ2 can be permitted.
C
Both REQ1 and REQ2 can be permitted.
D
Neither REQ1 nor REQ2 can be permitted
3
GATE CSE 2010
MCQ (Single Correct Answer)
+2
-0.6
A system has n resources R0,.....,Rn-1, and k processes P0,.....,Pk-1. The implementation of the resource request logic of each process Pi, is as follows:
if (i%2==0) {
  if (i < n) request Ri;
  if (i+2 < n) request Ri+2 ;
}
else {
  if (i < n) request Rn-i;
  if (i+2 < n) request Rn-i-2;
}
In which one of the following situations is a deadlock possible?
A
n = 40, k = 26
B
n = 21, k = 12
C
n = 20, k = 10
D
n = 41, k = 19
4
GATE CSE 2009
MCQ (Single Correct Answer)
+2
-0.6
Consider a system with 4 types of resources R1 (3 units), R2 (2 units), R3 (3 units), R4 (2 units). A non-preemptive resource allocation policy is used. At any given instance, a request is not entertained if it cannot be completely satisfied. Three processes P1, P2, P3 request the sources as follows if executed independently. GATE CSE 2009 Operating Systems - Deadlocks Question 13 English Which one of the following statements is TRUE if all three processes run concurrently starting at time t = 0?
A
All processes will finish without any deadlock
B
Only P1 and P2 will be in deadlock
C
Only P1 and P3 will be in deadlock
D
All three processes will be in deadlock
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