Circular Wait

• Attacking the Circular Wait Condition; Can circular waits exist? Order resources by an index: $R_1,R_2,\ldots$; requires that resources are always requested in order.
• One way to ensure that this condition never holds is to impose a total ordering of all resource types and to require that each process requests resources in an increasing order of enumeration.
• Assign to each resource type a unique integer number, which allows us to compare two resources and to determine whether one precedes another in our ordering.
• Each process can request resources only in an increasing order of enumeration.
• If these two protocols are used, then the circular-wait condition cannot hold.