Mastering Linux Kernel Development

Tick devices

The clock_event_device abstraction is for the core timing framework; we need a separate abstraction for tick devices per CPU; this is achieved through the structure struct tick_device and macro DEFINE_PER_CPU(), defined in kernel/time/tick-sched.h and include/linux/percpu-defs.h, respectively:

enum tick_device_mode { TICKDEV_MODE_PERIODIC, TICKDEV_MODE_ONESHOT,};struct tick_device {        struct clock_event_device *evtdev;        enum tick_device_mode mode;}

A tick_device could be either periodic or one shot. It's set through the enum tick_device_mode.