Liveness

In concurrent computing, liveness refers to a set of properties of concurrent systems, that require a system to make progress despite the fact that its concurrently executing components ("processes") may have to "take turns" in critical sections, parts of the program that cannot be simultaneously run by multiple processes. Liveness guarantees are important properties in operating systems and distributed systems.

A liveness property cannot be violated in a finite execution of a distributed system because the "good" event might only theoretically occur at some time after execution ends. Eventual consistency is an example of a liveness property. All properties can be expressed as the intersection of safety and liveness properties.

Several forms of liveness are recognized. The following ones are defined in terms of a multi-process system that has a critical section, protected by some mutual exclusion (mutex) device. All processes are assumed to correctly use the mutex; progress is defined as finishing execution of the critical section.

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