Assuming we have the following 3 processes trying to access 6 resources.

We know deadlock is possible. How can you change the order of resource requests so that there is no deadlock? Obviously, the critical region of each process cannot be changed, therefore, it must be ensured that all required resources are actually acquired.

void P2() void PO () { while (true) { get (A); get (B); get (C); // critical region: // use A, B, C release (A) ; release (B); release (C); } } void P1 () { while (true) { get (D); get (E); get (B); // critical region: // use D, E, B release (D); release (E) ; release (B); } } while (true) { get (C); get (F); get (D); // critical region: // use C, F, D release (C); release (F); release (D); }