GATE | GATE-CS-2015 (Set 3) | Question 65

Consider the following policies for preventing deadlock in a system with mutually exclusive resources.

I. Processes should acquire all their resources at the 
   beginning of execution.  If any resource is not  
   available, all resources acquired so far are released.
II. The resources are numbered uniquely, and processes are 
    allowed to request for resources only in increasing 
    resource numbers.
III. The resources are numbered uniquely, and processes are
     allowed to request  for resources only in decreasing 
     resource numbers.
IV. The resources are numbered uniquely. A process is allowed
    to request only for a resource with resource number larger
    than its currently held resources.

Which of the above policies can be used for preventing deadlock?
(A) Any one of I and III but not II or IV
(B) Any one of I, III and IV but not II
(C) Any one of II and III but not I or IV
(D) Any one of I, II, III and IV


Answer: (D)

Explanation: If Ist is followed, then hold and wait will never happen.

II, III and IV are similar. If any of these is followed, cyclic wait will not be possible.

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