Introduction

Deadlocks are a fundamental problem in distributed systems and deadlock detection in distributed systems has received considerable attention in the past. In distributed systems, a process may request resources in any order, which may not be known a priori, and a process can request a resource while holding others. If the allocation sequence of process resources is not controlled in such environments, deadlocks can occur. A deadlock can be defined as a condition where a set of processes request resources that are held by other processes in the set.

Deadlocks can be dealt with using any one of the following three strategies: deadlock prevention, deadlock avoidance, and deadlock detection. Deadlock prevention is commonly achieved by either having a process acquire all the needed resources simultaneously before it begins execution or by pre-empting a process that holds the needed resource. In the deadlock avoidance approach to distributed systems, a resource is granted to a process if the resulting global system is safe. Deadlock detection requires an examination of the status of the process–resources interaction for the presence of a deadlock condition. To resolve the deadlock, we have to abort a deadlocked process.

In this chapter, we study several distributed deadlock detection techniques based on various strategies.

System model

A distributed system consists of a set of processors that are connected by a communication network. The communication delay is finite but unpredictable.