Andrew S. Tanenbaum (OS) Edition 4 Exercise 6 Question 11 (Page No. 466)

Question

Suppose that there is a resource deadlock in a system. Give an example to show that the set of processes deadlocked can include processes that are not in the circular chain in the corresponding resource allocation graph.

Answer 1

Condition for deadlock: Cycle in resource allocation graph. (assuming single instance of every resource)

But it isn't required that only all the process in cycle are in deadlock. Process outside this cycle can be in deadlock.

Example:

A, B and C are process, X and Y are resource. A has X, B wants it. B has Y and A wants it. C wants X. All process are in deadlock.