Mastering Linux Kernel Development

Clock and Time Management

The Linux time management subsystem manages various time-related activities and keeps track of timing data such as current time and date, time elapsed since system boot up (system uptime) and timeouts, for example, how long to wait for a particular event to be initiated or terminated, locking the system after a timeout period has elapsed, or raising a signal to kill an unresponsive process.

There are two types of timing activities handled by the Linux time management subsystem:

• Keeping the current time and date
• Maintaining timers