Linux内核循环链表经典分析和移植

static inline void __list_add(struct list_head *new, struct list_head *prev,  struct list_head *next) 
{ 
    next->prev = new;
    new->next = next;        
    new->prev = prev;        
    prev->next = new; 
} 

static inline void list_add(struct list_head *new, struct  list_head *head) 
{ 
       __list_add(new, head, head->next); 
} 

static inline void list_add_tail(struct list_head *new, struct list_head *head) 
{ 
       __list_add(new, head->prev, head);
} 

static inline void __list_del(struct list_head * prev, struct list_head * next)
{ 
　　next->prev = prev;       
　　prev->next = next; 
} 

static inline void list_del(struct list_head *entry)
{ 
       __list_del(entry->prev, entry->next);        
　　　　entry->next = LIST_POISON1;        
　　　　entry->prev = LIST_POISON2; 
} 

static inline void list_del_init(struct list_head *entry)
{ 
       __list_del(entry->prev, entry->next);        
　　　　INIT_LIST_HEAD(entry); 
} 

static inline void list_move(struct list_head *list, struct list_head *head)
{ 
        __list_del(list->prev, list->next);         
　　　　list_add(list, head); 
} 

static inline void list_move_tail(struct list_head *list,    struct list_head *head) 
{ 
        __list_del(list->prev, list->next);        
　　　　 list_add_tail(list, head); 
} 

static inline int list_empty(const struct list_head *head) 
{ 
       return head->next == head; 
} 

static inline int list_empty_careful(const struct list_head *head) 
{ 
       struct list_head *next = head->next; 
       return (next == head) && (next == head->prev); 
} 

static inline void __list_splice(struct list_head *list, struct list_head *head)
{ 
       struct list_head *first = list->next;        
　　　　struct list_head *last  = list->prev;        
　　　　struct list_head *at    = head->next;   
       first->prev = head;        
　　　　head->next = first;   
       last->next = at;        
　　　　at->prev = last; 
} 

static inline void list_splice(struct list_head *list, struct list_head *head) 
{ 
       if (!list_empty(list)) 
       __list_splice(list, head); 
}   

typedef struct foo 
{    … 
    struct list_head list;    
 … 
};   

#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) 

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

　　#define list_entry(ptr, type, member) \ 
   　　 ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member))) 

#define list_for_each(pos, head) \ 
       for (pos = (head)->next; prefetch(pos->next), pos != (head); \                pos = pos->next) 

static inline void prefetch(void *x) 
{ 
      asm volatile("prefetcht0 %0" :: "m" (*(unsigned long *)x)); 
} 

#define __list_for_each(pos, head) \ 
       for (pos = (head)->next; pos != (head); pos = pos->next) 

/ * list_for_each_safe     -      iterate over a list safe against removal of list entry   */ 
#define list_for_each_safe(pos, n, head) \ 
       for (pos = (head)->next, n = pos->next; pos != (head); \              
　　　 　　 pos = n, n = pos->next) 

#define list_for_each_entry(pos, head, member)                       \ 
       for (pos = list_entry((head)->next, typeof(*pos), member);       \ 
            prefetch(pos->member.next), &pos->member != (head);        \ 
            pos = list_entry(pos->member.next, typeof(*pos), member)) 

#define list_prepare_entry(pos, head, member) \ 
       ((pos) ? : list_entry(head, typeof(*pos), member)) 

#define list_for_each_entry_continue(pos, head, member)         \ 
       for (pos = list_entry(pos->member.next, typeof(*pos), member);      \ 
            prefetch(pos->member.next), &pos->member != (head);  \
             pos = list_entry(pos->member.next, typeof(*pos), member)) 

#define list_for_each_entry_safe(pos, n, head, member)                   \
        for (pos = list_entry((head)->next, typeof(*pos), member),       \
               n = list_entry(pos->member.next, typeof(*pos), member);  \
              &pos->member != (head);                              \ 
              pos = n, n = list_entry(n->member.next, typeof(*n), member))

#define list_for_each_entry_safe_continue(pos, n, head, member)           \
        for (pos = list_entry(pos->member.next, typeof(*pos), member),    \
             n = list_entry(pos->member.next, typeof(*pos), member);      \
             &pos->member != (head);                                      \ 
             pos = n, n = list_entry(n->member.next, typeof(*n), member))

#ifndef __LIST_H
#define __LIST_H

/* This file is from Linux Kernel (include/linux/list.h) 
 * and modified by simply removing hardware prefetching of list items. 
 * Here by copyright, credits attributed to wherever they belong.
 * Kulesh Shanmugasundaram (kulesh [squiggly] isis.poly.edu)
 */

#define NULL (void *)0

#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)

#define container_of(ptr, type, member) ({                          const typeof( ((type *)0)->member ) *__mptr = (ptr);        (type *)( (char *)__mptr - offsetof(type,member) );})

/*
 * Simple doubly linked list implementation.
 *
 * Some of the internal functions ("__xxx") are useful when
 * manipulating whole lists rather than single entries, as
 * sometimes we already know the next/prev entries and we can
 * generate better code by using them directly rather than
 * using the generic single-entry routines.
 */

struct list_head {
    struct list_head *next, *prev;
};

#define LIST_HEAD_INIT(name) { &(name), &(name) }

#define LIST_HEAD(name)     struct list_head name = LIST_HEAD_INIT(name)

/*#define INIT_LIST_HEAD(ptr) do {     (ptr)->next = (ptr); (ptr)->prev = (ptr); } while (0)*/

static inline void INIT_LIST_HEAD(struct list_head *list)
{
    list->next = list;
    list->prev = list;
}

/*
 * Insert a new entry between two known consecutive entries. 
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_add(struct list_head *new,
                  struct list_head *prev,
                  struct list_head *next)
{
    next->prev = new;
    new->next = next;
    new->prev = prev;
    prev->next = new;
}

/**
 * list_add - add a new entry
 * @new: new entry to be added
 * @head: list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
static inline void list_add(struct list_head *new, struct list_head *head)
{
    __list_add(new, head, head->next);
}

/**
 * list_add_tail - add a new entry
 * @new: new entry to be added
 * @head: list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 */
static inline void list_add_tail(struct list_head *new, struct list_head *head)
{
    __list_add(new, head->prev, head);
}

/*
 * Delete a list entry by making the prev/next entries
 * point to each other.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_del(struct list_head *prev, struct list_head *next)
{
    next->prev = prev;
    prev->next = next;
}

/**
 * list_del - deletes entry from list.
 * @entry: the element to delete from the list.
 * Note: list_empty on entry does not return true after this, the entry is in an undefined state.
 */
static inline void list_del(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
    entry->next = (void *) 0;
    entry->prev = (void *) 0;
}

/**
 * list_del_init - deletes entry from list and reinitialize it.
 * @entry: the element to delete from the list.
 */
static inline void list_del_init(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
    INIT_LIST_HEAD(entry); 
}

/**
 * list_replace - replace old entry by new one
 * @old : the element to be replaced
 * @new : the new element to insert
 *
 * If @old was empty, it will be overwritten.
 */
static inline void list_replace(struct list_head *old,
                struct list_head *new)
{
    new->next = old->next;
    new->next->prev = new;
    new->prev = old->prev;
    new->prev->next = new;
}

static inline void list_replace_init(struct list_head *old,
                    struct list_head *new)
{
    list_replace(old, new);
    INIT_LIST_HEAD(old);
}

/**
 * list_move - delete from one list and add as another‘s head
 * @list: the entry to move
 * @head: the head that will precede our entry
 */
static inline void list_move(struct list_head *list, struct list_head *head)
{
        __list_del(list->prev, list->next);
        list_add(list, head);
}

/**
 * list_move_tail - delete from one list and add as another‘s tail
 * @list: the entry to move
 * @head: the head that will follow our entry
 */
static inline void list_move_tail(struct list_head *list,
                  struct list_head *head)
{
        __list_del(list->prev, list->next);
        list_add_tail(list, head);
}

/**
 * list_is_last - tests whether @list is the last entry in list @head
 * @list: the entry to test
 * @head: the head of the list
 */
static inline int list_is_last(const struct list_head *list,
                const struct list_head *head)
{
    return list->next == head;
}

/**
 * list_empty - tests whether a list is empty
 * @head: the list to test.
 */
static inline int list_empty(const struct list_head *head)
{
    return head->next == head;
}

/**
 * list_empty_careful - tests whether a list is empty and not being modified
 * @head: the list to test
 *
 * Description:
 * tests whether a list is empty _and_ checks that no other CPU might be
 * in the process of modifying either member (next or prev)
 *
 * NOTE: using list_empty_careful() without synchronization
 * can only be safe if the only activity that can happen
 * to the list entry is list_del_init(). Eg. it cannot be used
 * if another CPU could re-list_add() it.
 */
static inline int list_empty_careful(const struct list_head *head)
{
    struct list_head *next = head->next;
    return (next == head) && (next == head->prev);
}

/**
 * list_rotate_left - rotate the list to the left
 * @head: the head of the list
 */
static inline void list_rotate_left(struct list_head *head)
{
    struct list_head *first;

    if (!list_empty(head)) {
        first = head->next;
        list_move_tail(first, head);
    }
}

/**
 * list_is_singular - tests whether a list has just one entry.
 * @head: the list to test.
 */
static inline int list_is_singular(const struct list_head *head)
{
    return !list_empty(head) && (head->next == head->prev);
}

static inline void __list_cut_position(struct list_head *list,
        struct list_head *head, struct list_head *entry)
{
    struct list_head *new_first = entry->next;
    list->next = head->next;
    list->next->prev = list;
    list->prev = entry;
    entry->next = list;
    head->next = new_first;
    new_first->prev = head;
}

/**
 * list_cut_position - cut a list into two
 * @list: a new list to add all removed entries
 * @head: a list with entries
 * @entry: an entry within head, could be the head itself
 *    and if so we won‘t cut the list
 *
 * This helper moves the initial part of @head, up to and
 * including @entry, from @head to @list. You should
 * pass on @entry an element you know is on @head. @list
 * should be an empty list or a list you do not care about
 * losing its data.
 *
 */
static inline void list_cut_position(struct list_head *list,
        struct list_head *head, struct list_head *entry)
{
    if (list_empty(head))
        return;
    if (list_is_singular(head) &&
        (head->next != entry && head != entry))
        return;
    if (entry == head)
        INIT_LIST_HEAD(list);
    else
        __list_cut_position(list, head, entry);
}

static inline void __list_splice(const struct list_head *list,
                 struct list_head *prev,
                 struct list_head *next)
{
    struct list_head *first = list->next;
    struct list_head *last = list->prev;

    first->prev = prev;
    prev->next = first;

    last->next = next;
    next->prev = last;
}

/**
 * list_splice - join two lists, this is designed for stacks
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void list_splice(const struct list_head *list,
                struct list_head *head)
{
    if (!list_empty(list))
        __list_splice(list, head, head->next);
}

/**
 * list_splice_tail - join two lists, each list being a queue
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void list_splice_tail(struct list_head *list,
                struct list_head *head)
{
    if (!list_empty(list))
        __list_splice(list, head->prev, head);
}

/**
 * list_splice_init - join two lists and reinitialise the emptied list.
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 *
 * The list at @list is reinitialised
 */
static inline void list_splice_init(struct list_head *list,
                    struct list_head *head)
{
    if (!list_empty(list)) {
        __list_splice(list, head, head->next);
        INIT_LIST_HEAD(list);
    }
}

/**
 * list_splice_tail_init - join two lists and reinitialise the emptied list
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 *
 * Each of the lists is a queue.
 * The list at @list is reinitialised
 */
static inline void list_splice_tail_init(struct list_head *list,
                     struct list_head *head)
{
    if (!list_empty(list)) {
        __list_splice(list, head->prev, head);
        INIT_LIST_HEAD(list);
    }
}


/**
 * list_entry - get the struct for this entry
 * @ptr:    the &struct list_head pointer.
 * @type:    the type of the struct this is embedded in.
 * @member:    the name of the list_struct within the struct.
 */
#define list_entry(ptr, type, member) \
    ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

/**
 * list_first_entry - get the first element from a list
 * @ptr:    the list head to take the element from.
 * @type:    the type of the struct this is embedded in.
 * @member:    the name of the list_struct within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_first_entry(ptr, type, member) \
    list_entry((ptr)->next, type, member)

/**
 * list_first_entry_or_null - get the first element from a list
 * @ptr:    the list head to take the element from.
 * @type:    the type of the struct this is embedded in.
 * @member:    the name of the list_struct within the struct.
 *
 * Note that if the list is empty, it returns NULL.
 */
#define list_first_entry_or_null(ptr, type, member) \
    (!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)

/**
 * list_for_each    -    iterate over a list
 * @pos:    the &struct list_head to use as a loop cursor.
 * @head:    the head for your list.
 */
#define list_for_each(pos, head)     for (pos = (head)->next; pos != (head); pos = pos->next)

/**
 * __list_for_each    -    iterate over a list
 * @pos:    the &struct list_head to use as a loop cursor.
 * @head:    the head for your list.
 *
 * This variant doesn‘t differ from list_for_each() any more.
 * We don‘t do prefetching in either case.
 */
#define __list_for_each(pos, head)     for (pos = (head)->next; pos != (head); pos = pos->next)

/**
 * list_for_each_prev    -    iterate over a list backwards
 * @pos:    the &struct list_head to use as a loop cursor.
 * @head:    the head for your list.
 */
#define list_for_each_prev(pos, head)     for (pos = (head)->prev; pos != (head); pos = pos->prev)

/**
 * list_for_each_safe - iterate over a list safe against removal of list entry
 * @pos:    the &struct list_head to use as a loop cursor.
 * @n:        another &struct list_head to use as temporary storage
 * @head:    the head for your list.
 */
#define list_for_each_safe(pos, n, head)     for (pos = (head)->next, n = pos->next; pos != (head);         pos = n, n = pos->next)

/**
 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
 * @pos:    the &struct list_head to use as a loop cursor.
 * @n:        another &struct list_head to use as temporary storage
 * @head:    the head for your list.
 */
#define list_for_each_prev_safe(pos, n, head)     for (pos = (head)->prev, n = pos->prev;          pos != (head);          pos = n, n = pos->prev)

/**
 * list_for_each_entry    -    iterate over list of given type
 * @pos:    the type * to use as a loop cursor.
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 */
#define list_for_each_entry(pos, head, member)                    for (pos = list_entry((head)->next, typeof(*pos), member);             &pos->member != (head);              pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * list_for_each_entry_reverse - iterate backwards over list of given type.
 * @pos:    the type * to use as a loop cursor.
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member)                for (pos = list_entry((head)->prev, typeof(*pos), member);             &pos->member != (head);              pos = list_entry(pos->member.prev, typeof(*pos), member))

/**
 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
 * @pos:    the type * to use as a start point
 * @head:    the head of the list
 * @member:    the name of the list_struct within the struct.
 *
 * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
 */
#define list_prepare_entry(pos, head, member) \
    ((pos) ? : list_entry(head, typeof(*pos), member))

/**
 * list_for_each_entry_continue - continue iteration over list of given type
 * @pos:    the type * to use as a loop cursor.
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 *
 * Continue to iterate over list of given type, continuing after
 * the current position.
 */
#define list_for_each_entry_continue(pos, head, member)             for (pos = list_entry(pos->member.next, typeof(*pos), member);             &pos->member != (head);             pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * list_for_each_entry_continue_reverse - iterate backwards from the given point
 * @pos:    the type * to use as a loop cursor.
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 *
 * Start to iterate over list of given type backwards, continuing after
 * the current position.
 */
#define list_for_each_entry_continue_reverse(pos, head, member)            for (pos = list_entry(pos->member.prev, typeof(*pos), member);             &pos->member != (head);             pos = list_entry(pos->member.prev, typeof(*pos), member))

/**
 * list_for_each_entry_from - iterate over list of given type from the current point
 * @pos:    the type * to use as a loop cursor.
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 *
 * Iterate over list of given type, continuing from current position.
 */
#define list_for_each_entry_from(pos, head, member)                 for (; &pos->member != (head);             pos = list_entry(pos->member.next, typeof(*pos), member))

/**
 * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @pos:    the type * to use as a loop cursor.
 * @n:        another type * to use as temporary storage
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member)                for (pos = list_entry((head)->next, typeof(*pos), member),            n = list_entry(pos->member.next, typeof(*pos), member);             &pos->member != (head);                              pos = n, n = list_entry(n->member.next, typeof(*n), member))

/**
 * list_for_each_entry_safe_continue - continue list iteration safe against removal
 * @pos:    the type * to use as a loop cursor.
 * @n:        another type * to use as temporary storage
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 *
 * Iterate over list of given type, continuing after current point,
 * safe against removal of list entry.
 */
#define list_for_each_entry_safe_continue(pos, n, head, member)             for (pos = list_entry(pos->member.next, typeof(*pos), member),                 n = list_entry(pos->member.next, typeof(*pos), member);                 &pos->member != (head);                                 pos = n, n = list_entry(n->member.next, typeof(*n), member))

/**
 * list_for_each_entry_safe_from - iterate over list from current point safe against removal
 * @pos:    the type * to use as a loop cursor.
 * @n:        another type * to use as temporary storage
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 *
 * Iterate over list of given type from current point, safe against
 * removal of list entry.
 */
#define list_for_each_entry_safe_from(pos, n, head, member)                 for (n = list_entry(pos->member.next, typeof(*pos), member);                 &pos->member != (head);                                 pos = n, n = list_entry(n->member.next, typeof(*n), member))

/**
 * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
 * @pos:    the type * to use as a loop cursor.
 * @n:        another type * to use as temporary storage
 * @head:    the head for your list.
 * @member:    the name of the list_struct within the struct.
 *
 * Iterate backwards over list of given type, safe against removal
 * of list entry.
 */
#define list_for_each_entry_safe_reverse(pos, n, head, member)            for (pos = list_entry((head)->prev, typeof(*pos), member),            n = list_entry(pos->member.prev, typeof(*pos), member);             &pos->member != (head);                              pos = n, n = list_entry(n->member.prev, typeof(*n), member))

/**
 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
 * @pos:    the loop cursor used in the list_for_each_entry_safe loop
 * @n:        temporary storage used in list_for_each_entry_safe
 * @member:    the name of the list_struct within the struct.
 *
 * list_safe_reset_next is not safe to use in general if the list may be
 * modified concurrently (eg. the lock is dropped in the loop body). An
 * exception to this is if the cursor element (pos) is pinned in the list,
 * and list_safe_reset_next is called after re-taking the lock and before
 * completing the current iteration of the loop body.
 */
#define list_safe_reset_next(pos, n, member)                \
    n = list_entry(pos->member.next, typeof(*pos), member)

#endif