Deadlock

Using a diagram called the Resource-Allocation graph, we can, in may cases, learn if a deadlock occurs.

This graph contains the following components:

1. Resource categories: {R₀, R₁, R₂, ..., R_M}, which we show on the graph using square box nodes. Each box will contain at least one dot to indicate specific instances of a resource. For instance, two dots might represent two laser printers.)
2. Processes: {P₀, P₁, P₂, ..., P_N}. The # of processes might be different from this of resource categories.
3. Request arrows. An arrow from some process P_i to some resource category R_j indicates that P_i wants to use an instance of R_j. It doesn't matter which instance will be used since any instance of this resource will do.
4. Assignment arrows. An arrow from an instance (dot) of some resource R_j to some process P_i tells that this specific instance of R_j is currently held by process P_i.