Chapter 10. Project: Virtual Timers

Many systems create multiple "virtual" timers from a single hardware timer. This chapter develops application-level virtual timers based on a single operating system timer. The project explores timers, signals and the testing of asynchronous programs with timed input. Special care must be taken in blocking and unblocking the signals at the right times. The project emphasizes careful, modular design by specifying a well-defined interface between the user -implemented virtual timers and the underlying timer facility.

Objectives

• Learn about testing and timing

• Experiment with POSIX interval timers

• Explore implications of asynchronous operation

• Use POSIX realtime signals

• Understand timer implementation