Understanding the Linux Kernel list.h Linked List Implementation

Linux kernel contains many classic data structures, and the list linked list is one of them. This article introduces the list definition, its operations, precautions, and usage examples.

Contents

list definition

list operations

precautions

usage example

File locations

All list operations are defined in include/linux/list.h . The list_head definition is in include/linux/types.h .

Definition

The list is a doubly‑circular linked list with a head pointer. The list_head structure contains only forward and backward pointers and is meant to be embedded in user‑defined structs to chain them together.

Operations

Initialization

Insertion

Insert a new element between two existing elements (the basis for head and tail insertion).

Head insertion places the new element between the head and the first element; tail insertion places it between the last element and the head (because the list is circular).

Deletion

Remove an element between two others or delete a known entry.

Replacement

Pointer manipulation to replace one element with another.

Move

Move an element to the head or tail of another list.

Split

Divide a list at a specified entry into two separate lists.

Merge

Insert one list into another at the head or tail.

list_entry macro

The macro uses the embedded list_head pointer to retrieve the containing struct via the classic Linux container_of macro.

Various helper macros are provided for traversal and entry retrieval.

Precautions

When multiple threads operate on the same list, proper locking is required.

Usage Example