Short answer practice

Question 1

What protocol can we use to ensure the circular-wait condition cannot hold (deadlock prevention)

Answer 1

Let the set of threads involved in the circular wait be {T0,,,,,Tn). Ti will be requesting Ri which is being held by Ti + 1, which in turn will be requesting Ri + 1. We must have F(Ri) < F(Ri+1) for all i. This condition means that F(R0) < F(R1) <,,,,< F(Rn) < F(R0). By transitivity F(R0) < F(R0) which is impossible. Therefore there can be no circular wait.