# Concepts

This chapter describes various concepts which are used in the Linux kernel.

* [Per-CPU variables](https://0xax.gitbook.io/linux-insides/summary/concepts/linux-cpu-1)
* [CPU masks](https://0xax.gitbook.io/linux-insides/summary/concepts/linux-cpu-2)
* [The initcall mechanism](https://0xax.gitbook.io/linux-insides/summary/concepts/linux-cpu-3)
* [Notification Chains](https://0xax.gitbook.io/linux-insides/summary/concepts/linux-cpu-4)