Operating systems miscellaneous Easy Questions and Answers | Page - 17

Operating systems miscellaneous

Which of the following is not true for deadlock prevention and deadlock avoidance schemes?

1. In deadlock prevention, the request for resources is always granted, if the resulting state is safe
1. In deadlock avoidance, the request for resources is always granted, if the resulting state is safe
1. Deadlock avoidance is less restrictive than deadlock prevention
1. Deadlock avoidance requires knowledge of resource requirement a priori

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Deadlock prevention does not guarantee the state that the state would be safe when the request for resources is granted instead it is guaranteed by deadlock avoidance and there will be no deadlock at that time.

Correct Option: A

Deadlock prevention does not guarantee the state that the state would be safe when the request for resources is granted instead it is guaranteed by deadlock avoidance and there will be no deadlock at that time.

Consider a system with 4 types of resources R₁ (3 units), R₂ (2 unit), R₃ (3 unit), R₄ (2 unit). A non-pre-emptive 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 resource as follows, if executed independently.

Which one of the following statements is true, if all three processes run concurrently starting at time t = 0?

1. All processes will finish without any deadlock
1. P₁ and P₂ will be in deadlock
1. P₁ and P₃ will be in deadlock
1. All three processes will be in deadlock

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The Bolded line show that at that time the requirement of resource is less than avaiability but it does not cause dead lock. All process finish without any dead lock

Correct Option: A

The Bolded line show that at that time the requirement of resource is less than avaiability but it does not cause dead lock. All process finish without any dead lock

A system has n resources R₀, ..... R_{n - 1}, and k processes P₀, .... P_{k - 1}. The implementation of the resources request logic of each process P_i, is as follows if (i% 2 = = 0) {
if (i < n) request R_i;
   if (i + 2 < n) request R_{i + 2};
}
else {
  if (i < n) request R_{n - i};
  if (i + 2 < n) request R_{n - i - 2};
}
In which one of the following situations is a deadlock possible?

1. n = 40, k = 26
1. n = 21, k = 12
1. n = 20, k = 10
1. n = 41, k = 19

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NA

Correct Option: B

NA

A system contains three programs and each requires three tape units for its operation. The minimum number of tape units which the system must have such that deadlocks never arise is _________.

1. 10
1. 7
1. 12
1. 5

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NA

Correct Option: B

NA

Consider the procedure below for the Producer-Consumer problem which uses semaphores :
semaphore n = 0;
semaphore s = 1;

Which one of the following is TRUE ?

1. The producer will be able to add an item to the buffer, but the consumer can never consume it.
1. The consumer will remove no more than one item from the buffer.
1. Deadlock occurs if the consumer succeeds in acquiring semaphore s when the buffer is empty.
1. The starting value for the semaphore n must be 1 and not 0 for deadlock-free operation.

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Consumer executes wait (S), then wait (n) and goes to sleep by decreasing n value.
After the consumer sleep, producer goes to the sleep by executing wait (s).
Dead lock occurs if the consumers succeeds in aquiring semaphore S when the buffer is empty.

Correct Option: C

Consumer executes wait (S), then wait (n) and goes to sleep by decreasing n value.
After the consumer sleep, producer goes to the sleep by executing wait (s).
Dead lock occurs if the consumers succeeds in aquiring semaphore S when the buffer is empty.

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