Interprocess Communications in Linux®: The Nooks & Crannies

Chapter 7. Semaphores

Introduction

Conceptually, a semaphore is a data structure that is shared by several processes.^[1] Semaphores are most often used to synchronize operations when multiple processes access a common, non-shareable resource. By using semaphores, we attempt to avoid starvation (which occurs when a process is habitually denied access to a resource it needs) and deadlock (which occurs when two or more processes each hold a resource that the other needs while waiting for the other process to release its resource). When used to synchronize the access to a resource, a semaphore is initially set to the number of available resources. Each ...