1. kernel data structures

2. outline linked list queues maps binary trees algorithmic complexity

3. singly linked lists

4. doubly lined lists

5. circular linked lists

6. the Linux kernel’s implementation The linked-list code is declared in the header file and the data structure is simple

7. usage

8. container_of() Using the macro container_of(), we can easily find the parent structure containing any given member variable. #define container_of(ptr, type, member) ({ \ const typeof( ((type *)0)->member ) *__mptr = (ptr); \ (type *)( (char *)__mptr - offsetof(type,member) );})

9. container_of() #define container_of(ptr, type, member) ({ \ const typeof( ((type *)0)->member ) *__mptr = (ptr); \ (type *)( (char *)__mptr - offsetof(type,member) );}) list_head 0x00 0xYZ offset = 0xYZ

10. container_of() #define container_of(ptr, type, member) ({ \ const typeof( ((type *)0)->member ) *__mptr = (ptr); \ (type *)( (char *)__mptr - offsetof(type,member) );}) list_head member offset = 0xYZ container

11. // Keil 8051 compiler #define offsetof(s,m) (size_t)&(((s *)0)->m) // Microsoft x86 compiler (version 7) #define offsetof(s,m) (size_t)(unsigned long)&(((s *)0)->m) // Diab Coldfire compiler #define offsetof(s,memb) ((size_t)((char *)&((s *)0)->memb-(char *)0) offsetof

12. 1.((s *)0) takes the integer zero and casts it as a pointer to s. 2.((s *)0)->m dereferences that pointer to point to structure member m. 3.&(((s *)0)->m) computes the address of m. 4.(size_t)&(((s *)0)->m) casts the result to an appropriate data type. offsetof in Keil’s C reference: http://blog.linux.org.tw/~jserv/archives/001399.html

13. functions list_addlist_add — add a new entry list_dellist_del — deletes entry from list list_movelist_move — delete from one list and add as another's head list_emptylist_empty — tests whether a list is empty list_entrylist_entry — get the struct for this entry list_for_eachlist_for_each — iterate over a list list_for_each_entrylist_for_each_entry — iterate over list of given type

14. #define list_entry(ptr, type, member) \ container_of(ptr, type, member) list_entry

15. QUEUES

16. kfifo Linux’s kfifo works like most other queue abstractions, providing two primary operations: – enqueue (unfortunately named in ) and – dequeue (out ). The kfifo object maintains two offsets into the queue: an in offset and an out offset. The enqueue (in) operation copies data into the queue, starting at the in offset.

17. functions kfifo_reset — removes the entire FIFO contents kfifo_reset kfifo_put — puts some data into the FIFO kfifo_put kfifo_get — gets some data from the FIFO kfifo_get kfifo_len — returns the number of bytes available in the FIFO kfifo_len kfifo_init — allocates a new FIFO using a preallocated buffer kfifo_init kfifo_alloc — allocates a new FIFO and its internal buffer kfifo_alloc kfifo_free — frees the FIFO kfifo_free

18. MAPS

19. definition A map, also known as an associative array, is a collection of unique keys, where each key is associated with a specific value. The relationship between a key and its value is called a mapping. Maps support at least three operations:

20. definition: operator Add (key, value) Remove (key) value = Lookup (key)

21. implementation The Linux kernel provides a simple and efficient map data structure, but it is not a general-purpose map It is designed for one specific use case: mapping a unique identification number (UID) to a pointer.