Wait-For Graph

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A Wait-For Graph in computer science is a graph used for deadlock detection in operating systems and relational database systems.

In Computer Science, a system that allows concurrent operation of multiple processes and locking of resources and which does not provide mechanisms to avoid or prevent deadlock must support a mechanism to detect deadlocks and an algorithm for recovering from them.

One such deadlock detection algorithm makes use of a Wait-For Graph to track which other processes a process is currently blocking on. In a Wait-for Graph, processes are represented as nodes, and an edge from process $P i$ to $P j$ implies $P j$ is holding a resource that $P i$ needs and thus $P i$ is waiting for $P j$ to release its lock on that resource.