ISRO-DEC2017-64

Question

Which of the following is not true with respect to deadlock prevention and deadlock avoidance schemes?

• A. In deadlock prevention, the request for resources is always granted if resulting state is safe.
• B. In deadlock avoidance, the request for resources is always granted. if the resulting state is safe.
• C. Deadlock avoidance requires knowledge of resource requirements a priori.
• D. Deadlock prevention is more restrictive than deadlock avoidance.

Comments

option a

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option A is false because it is a condition for deadlock avoidance not prevention

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https://gateoverflow.in/488/gate-cse-2008-question-65

Answer 1

Deadlock prevention tries to break one of the four necessary conditions of deadlock. It may reject resource requests even if the resulting state is safe in order to break necessary condition.

Eg: ordering of resources may reject some requests even though they are safe

• Prevention is similar to a traffic light while avoidance is similar to a police officer directing traffic
• Deadlock avoidance is less strict than deadlock prevention. It allows mutual exclusion, wait and hold, no preemption, but prevents circular wait. Deadlock avoidance only checks safe states. The request for resources is always granted if the resulting state is safe

Option A is false, all other options are true

Answer 2

option A

Deadlock prevention scheme handles deadlock by making sure that one of the four necessary conditions don't occur. In deadlock prevention, the request for a resource may not be granted even if the resulting state is safe.

http://www.geeksforgeeks.org/operating-systems-set-11/