Linux Kernel Development, Second Edition

Chapter 8. Kernel Synchronization Introduction

In a shared memory application, care must be taken to ensure that shared resources are protected from concurrent access. The kernel is no exception. Shared resources require protection from concurrent access because if multiple threads of execution^[1] access and manipulate the data at the same time, the threads may overwrite each other's changes or access data while it is in an inconsistent state. Concurrent access of shared data is a recipe for instability that often proves very hard to track down and debug—getting it right off the bat is important.

Properly protecting shared resources can be tough. Years ago, before Linux supported symmetrical multiprocessing, preventing concurrent access of data ...