Process Synchronization and Election Algorithms

Process synchronization is the set of techniques that are used to coordinate execution amongst processes. For example, a process may wish to run only to a certain point, at which it will stop and wait for another process to finish certain actions. A common resource (such as a device or a location in memory) may require exclusive access and processes have to coordinate amongst themselves to ensure that access is fair and exclusive. In centralized systems, it was common enforce exclusive access to shared code. Mutual exclusion was accomplished through mechanisms such as test and set locks in hardware and semaphores, messages, and condition variables in software. We will now revisit the topic of mutual exclusion in distributed systems. We assume that there is group agreement on how a critical section (or exclusive resource) is identified (e.g. name, number) and that this identifier is passed as a parameter with any requests.