11.1. Introduction

We discussed processes in earlier chapters. We learned about the environment of a UNIX process, the relationships between processes, and ways to control processes. We saw that a limited amount of sharing can occur between related processes.

In this chapter, we'll look inside a process further to see how we can use multiple threads of control (or simply threads) to perform multiple tasks within the environment of a single process. All threads within a single process have access to the same process components, such as file descriptors and memory.

Any time you try to share a single resource among multiple users, you have to deal with consistency. We'll conclude the chapter with a look at the synchronization mechanisms available to prevent multiple threads from viewing inconsistencies in their shared resources.