linux list.h 实例

=======================my_list.h==================================

#ifndef __MY_LIST_H__
#define __MY_LIST_H__
#ifdef __KERNEL__


#include <linux/stddef.h>
#include <linux/poison.h>
#include <linux/prefetch.h>
#include <asm/system.h>


/*
PORTINGNOTE
Faking functions that are not available in userspace
*/


#elif 1
static int prefetch;
#define prefetch(x) prefetch=0
#define smp_wmb()


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


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


#define LPNLNODE(p)     ((struct list_head *)p)


/*
PORTINGNOTE: these poison definition has been moved to <linux/poison.h> in newer linux kernel


 * These are non-NULL pointers that will result in page faults
 * under normal circumstances, used to verify that nobody uses
 * non-initialized list entries.
 */
#define LIST_POISON1  ((void *) 0x00100100)
#define LIST_POISON2  ((void *) 0x00200200)


/*
 * 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)


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!
 */
#ifndef CONFIG_DEBUG_LIST
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;
}
#else
extern void __list_add(struct list_head *new,
      struct list_head *prev, struct list_head *next);
#endif


/**
 * 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.
 */
#ifndef CONFIG_DEBUG_LIST
static inline void
list_add(struct list_head *new, struct list_head *head)
{
__list_add(new, head, head->next);
}
#else
extern void list_add(struct list_head *new, struct list_head *head);
#endif


/**
 * 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);
}


/*
 * 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_rcu(struct list_head *new,
      struct list_head *prev, struct list_head *next)
{
new->next = next;
new->prev = prev;
smp_wmb();
next->prev = new;
prev->next = new;
}


/**
 * list_add_rcu - add a new entry to rcu-protected list
 * @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.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as list_add_rcu()
 * or list_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * list_for_each_entry_rcu().
 */
static inline void
list_add_rcu(struct list_head *new, struct list_head *head)
{
__list_add_rcu(new, head, head->next);
}


/**
 * list_add_tail_rcu - add a new entry to rcu-protected list
 * @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.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as list_add_tail_rcu()
 * or list_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * list_for_each_entry_rcu().
 */
static inline void
list_add_tail_rcu(struct list_head *new, struct list_head *head)
{
__list_add_rcu(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.
 */
#ifndef CONFIG_DEBUG_LIST
static inline void
list_del(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
entry->next = LIST_POISON1;
entry->prev = LIST_POISON2;
}
#else
extern void list_del(struct list_head *entry);
#endif


/**
 * list_del_rcu - deletes entry from list without re-initialization
 * @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. It is useful for RCU based
 * lockfree traversal.
 *
 * In particular, it means that we can not poison the forward
 * pointers that may still be used for walking the list.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as list_del_rcu()
 * or list_add_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * list_for_each_entry_rcu().
 *
 * Note that the caller is not permitted to immediately free
 * the newly deleted entry.  Instead, either synchronize_rcu()
 * or call_rcu() must be used to defer freeing until an RCU
 * grace period has elapsed.
 */
static inline void
list_del_rcu(struct list_head *entry)
{
__list_del(entry->prev, entry->next);
entry->prev = LIST_POISON2;
}


/**
 * 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_replace_rcu - replace old entry by new one
 * @old : the element to be replaced
 * @new : the new element to insert
 *
 * The @old entry will be replaced with the @new entry atomically.
 * Note: @old should not be empty.
 */
static inline void
list_replace_rcu(struct list_head *old, struct list_head *new)
{
new->next = old->next;
new->prev = old->prev;
smp_wmb();
new->next->prev = new;
new->prev->next = new;
old->prev = LIST_POISON2;
}


/**
 * 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_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);
}


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;
}


/**
 * list_splice - join two lists
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void
list_splice(struct list_head *list, struct list_head *head)
{
if (!list_empty(list))
__list_splice(list, 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);
INIT_LIST_HEAD(list);
}
}


/**
 * list_splice_init_rcu - splice an RCU-protected list into an existing list.
 * @list: the RCU-protected list to splice
 * @head: the place in the list to splice the first list into
 * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ...
 *
 * @head can be RCU-read traversed concurrently with this function.
 *
 * Note that this function blocks.
 *
 * Important note: the caller must take whatever action is necessary to
 * prevent any other updates to @head.  In principle, it is possible
 * to modify the list as soon as sync() begins execution.
 * If this sort of thing becomes necessary, an alternative version
 * based on call_rcu() could be created.  But only if -really-
 * needed -- there is no shortage of RCU API members.
 */
static inline void
list_splice_init_rcu(struct list_head *list,
    struct list_head *head, void (*sync) (void))
{
struct list_head *first = list->next;
struct list_head *last = list->prev;
struct list_head *at = head->next;


if (list_empty(head))
return;


/* "first" and "last" tracking list, so initialize it. */


INIT_LIST_HEAD(list);


/*
* At this point, the list body still points to the source list.
* Wait for any readers to finish using the list before splicing
* the list body into the new list.  Any new readers will see
* an empty list.
*/


sync();


/*
* Readers are finished with the source list, so perform splice.
* The order is important if the new list is global and accessible
* to concurrent RCU readers.  Note that RCU readers are not
* permitted to traverse the prev pointers without excluding
* this function.
*/


last->next = at;
smp_wmb();
head->next = first;
first->prev = head;
at->prev = last;
}


/**
 * 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) \
container_of(ptr, type, member)


/**
 * 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; prefetch(pos->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 differs from list_for_each() in that it's the
 * simplest possible list iteration code, no prefetching is done.
 * Use this for code that knows the list to be very short (empty
 * or 1 entry) most of the time.
 */
#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; prefetch(pos->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_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);\
    prefetch(pos->member.next), &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);\
    prefetch(pos->member.prev), &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);\
    prefetch(pos->member.next), &pos->member != (head);\
    pos = list_entry(pos->member.next, 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 (; prefetch(pos->member.next), &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
 * @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
 * @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
 * @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_for_each_rcu -iterate over an rcu-protected list
 * @pos: the &struct list_head to use as a loop cursor.
 * @head: the head for your list.
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as list_add_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
#define list_for_each_rcu(pos, head) \
for (pos = (head)->next; \
prefetch(rcu_dereference(pos)->next), pos != (head); \
         pos = pos->next)


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


/**
 * list_for_each_safe_rcu
 * @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.
 *
 * Iterate over an rcu-protected list, safe against removal of list entry.
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as list_add_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
#define list_for_each_safe_rcu(pos, n, head) \
for (pos = (head)->next; \
n = rcu_dereference(pos)->next, pos != (head); \
pos = n)


/**
 * list_for_each_entry_rcu -iterate over rcu 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.
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as list_add_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
#define list_for_each_entry_rcu(pos, head, member) \
for (pos = list_entry((head)->next, typeof(*pos), member); \
prefetch(rcu_dereference(pos)->member.next), \
&pos->member != (head); \
pos = list_entry(pos->member.next, typeof(*pos), member))


/**
 * list_for_each_continue_rcu
 * @pos: the &struct list_head to use as a loop cursor.
 * @head: the head for your list.
 *
 * Iterate over an rcu-protected list, continuing after current point.
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as list_add_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
#define list_for_each_continue_rcu(pos, head) \
for ((pos) = (pos)->next; \
prefetch(rcu_dereference((pos))->next), (pos) != (head); \
         (pos) = (pos)->next)


/**
 * list_count
 * @list: the head for your list.
 *
 * count the list node num
 *
 */
static inline unsigned int
list_count(struct list_head *list)
{
unsigned int ret;
struct list_head *pos;


ret = 0;
list_for_each(pos, list) {
ret++;
}


return ret;
}


/*
 * Double linked lists with a single pointer list head.
 * Mostly useful for hash tables where the two pointer list head is
 * too wasteful.
 * You lose the ability to access the tail in O(1).
 */


struct hlist_head {
struct hlist_node *first;
};


struct hlist_node {
struct hlist_node *next, **pprev;
};


#define HLIST_HEAD_INIT { .first = NULL }
#define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
static inline void
INIT_HLIST_NODE(struct hlist_node *h)
{
h->next = NULL;
h->pprev = NULL;
}


static inline int
hlist_unhashed(const struct hlist_node *h)
{
return !h->pprev;
}


static inline int
hlist_empty(const struct hlist_head *h)
{
return !h->first;
}


static inline void
__hlist_del(struct hlist_node *n)
{
struct hlist_node *next = n->next;
struct hlist_node **pprev = n->pprev;
*pprev = next;
if (next)
next->pprev = pprev;
}


static inline void
hlist_del(struct hlist_node *n)
{
__hlist_del(n);
n->next = LIST_POISON1;
n->pprev = LIST_POISON2;
}


/**
 * hlist_del_rcu - deletes entry from hash list without re-initialization
 * @n: the element to delete from the hash list.
 *
 * Note: list_unhashed() on entry does not return true after this,
 * the entry is in an undefined state. It is useful for RCU based
 * lockfree traversal.
 *
 * In particular, it means that we can not poison the forward
 * pointers that may still be used for walking the hash list.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_add_head_rcu()
 * or hlist_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_for_each_entry().
 */
static inline void
hlist_del_rcu(struct hlist_node *n)
{
__hlist_del(n);
n->pprev = LIST_POISON2;
}


static inline void
hlist_del_init(struct hlist_node *n)
{
if (!hlist_unhashed(n)) {
__hlist_del(n);
INIT_HLIST_NODE(n);
}
}


/**
 * hlist_replace_rcu - replace old entry by new one
 * @old : the element to be replaced
 * @new : the new element to insert
 *
 * The @old entry will be replaced with the @new entry atomically.
 */
static inline void
hlist_replace_rcu(struct hlist_node *old, struct hlist_node *new)
{
struct hlist_node *next = old->next;


new->next = next;
new->pprev = old->pprev;


smp_wmb();
if (next)
new->next->pprev = &new->next;
*new->pprev = new;
old->pprev = LIST_POISON2;
}


static inline void
hlist_add_head(struct hlist_node *n, struct hlist_head *h)
{
struct hlist_node *first = h->first;
n->next = first;
if (first)
first->pprev = &n->next;
h->first = n;
n->pprev = &h->first;
}


/**
 * hlist_add_head_rcu
 * @n: the element to add to the hash list.
 * @h: the list to add to.
 *
 * Description:
 * Adds the specified element to the specified hlist,
 * while permitting racing traversals.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_add_head_rcu()
 * or hlist_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_for_each_entry_rcu(), used to prevent memory-consistency
 * problems on Alpha CPUs.  Regardless of the type of CPU, the
 * list-traversal primitive must be guarded by rcu_read_lock().
 */
static inline void
hlist_add_head_rcu(struct hlist_node *n, struct hlist_head *h)
{
struct hlist_node *first = h->first;
n->next = first;
n->pprev = &h->first;
smp_wmb();
if (first)
first->pprev = &n->next;
h->first = n;
}


/* next must be != NULL */
static inline void
hlist_add_before(struct hlist_node *n, struct hlist_node *next)
{
n->pprev = next->pprev;
n->next = next;
next->pprev = &n->next;
*(n->pprev) = n;
}


static inline void
hlist_add_after(struct hlist_node *n, struct hlist_node *next)
{
next->next = n->next;
n->next = next;
next->pprev = &n->next;


if (next->next)
next->next->pprev = &next->next;
}


/**
 * hlist_add_before_rcu
 * @n: the new element to add to the hash list.
 * @next: the existing element to add the new element before.
 *
 * Description:
 * Adds the specified element to the specified hlist
 * before the specified node while permitting racing traversals.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_add_head_rcu()
 * or hlist_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_for_each_entry_rcu(), used to prevent memory-consistency
 * problems on Alpha CPUs.
 */
static inline void
hlist_add_before_rcu(struct hlist_node *n, struct hlist_node *next)
{
n->pprev = next->pprev;
n->next = next;
smp_wmb();
next->pprev = &n->next;
*(n->pprev) = n;
}


/**
 * hlist_add_after_rcu
 * @prev: the existing element to add the new element after.
 * @n: the new element to add to the hash list.
 *
 * Description:
 * Adds the specified element to the specified hlist
 * after the specified node while permitting racing traversals.
 *
 * The caller must take whatever precautions are necessary
 * (such as holding appropriate locks) to avoid racing
 * with another list-mutation primitive, such as hlist_add_head_rcu()
 * or hlist_del_rcu(), running on this same list.
 * However, it is perfectly legal to run concurrently with
 * the _rcu list-traversal primitives, such as
 * hlist_for_each_entry_rcu(), used to prevent memory-consistency
 * problems on Alpha CPUs.
 */
static inline void
hlist_add_after_rcu(struct hlist_node *prev, struct hlist_node *n)
{
n->next = prev->next;
n->pprev = &prev->next;
smp_wmb();
prev->next = n;
if (n->next)
n->next->pprev = &n->next;
}


#define hlist_entry(ptr, type, member) container_of(ptr,type,member)


#define hlist_for_each(pos, head) \
for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \
    pos = pos->next)


#define hlist_for_each_safe(pos, n, head) \
for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \
    pos = n)


/**
 * hlist_for_each_entry - iterate over list of given type
 * @tpos: the type * to use as a loop cursor.
 * @pos: the &struct hlist_node to use as a loop cursor.
 * @head: the head for your list.
 * @member: the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry(tpos, pos, head, member)\
for (pos = (head)->first;\
    pos && ({ prefetch(pos->next); 1;}) &&\
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
    pos = pos->next)


/**
 * hlist_for_each_entry_continue - iterate over a hlist continuing after current point
 * @tpos: the type * to use as a loop cursor.
 * @pos: the &struct hlist_node to use as a loop cursor.
 * @member: the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_continue(tpos, pos, member)\
for (pos = (pos)->next;\
    pos && ({ prefetch(pos->next); 1;}) &&\
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
    pos = pos->next)


/**
 * hlist_for_each_entry_from - iterate over a hlist continuing from current point
 * @tpos: the type * to use as a loop cursor.
 * @pos: the &struct hlist_node to use as a loop cursor.
 * @member: the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_from(tpos, pos, member)\
for (; pos && ({ prefetch(pos->next); 1;}) &&\
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
    pos = pos->next)


/**
 * hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry
 * @tpos: the type * to use as a loop cursor.
 * @pos: the &struct hlist_node to use as a loop cursor.
 * @n: another &struct hlist_node to use as temporary storage
 * @head: the head for your list.
 * @member: the name of the hlist_node within the struct.
 */
#define hlist_for_each_entry_safe(tpos, pos, n, head, member) \
for (pos = (head)->first;\
    pos && ({ n = pos->next; 1; }) && \
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
    pos = n)


/**
 * hlist_for_each_entry_rcu - iterate over rcu list of given type
 * @tpos: the type * to use as a loop cursor.
 * @pos: the &struct hlist_node to use as a loop cursor.
 * @head: the head for your list.
 * @member: the name of the hlist_node within the struct.
 *
 * This list-traversal primitive may safely run concurrently with
 * the _rcu list-mutation primitives such as hlist_add_head_rcu()
 * as long as the traversal is guarded by rcu_read_lock().
 */
#define hlist_for_each_entry_rcu(tpos, pos, head, member)\
for (pos = (head)->first;\
    rcu_dereference(pos) && ({ prefetch(pos->next); 1;}) &&\
({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
    pos = pos->next)


/*add by shaojunwu */
static inline int
is_entry_in_list(struct list_head *entry, struct list_head *head)
{
struct list_head *pos = NULL;


list_for_each(pos, head) {
if (pos == entry) {
return 1;
}
}


return 0;
}


static inline int
is_entry_in_hlist(struct hlist_node *entry, struct hlist_head *head)
{
struct hlist_node *pos = NULL;


hlist_for_each(pos, head) {
if (pos == entry) {
return 1;
}
}


return 0;
}


#else
#warning "don't include kernel headers in userspace"
#endif /* __KERNEL__ */
#endif

=====================main.c=========================================

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include "my_list.h"


struct kool_list{
    int to;
    struct list_head list;
    int from;
};


int main(int argc,char**argv)
{
unsigned int i;
    struct kool_list *tmp;
    struct list_head *pos, *q;    
    struct kool_list mylist;

    INIT_LIST_HEAD(&mylist.list);

    for(i=3; i!=0; --i){
        tmp = (struct kool_list*)malloc(sizeof(struct kool_list));
        printf("enter to and from:");
        scanf("%d %d", &tmp->to, &tmp->from);
        list_add(&(tmp->list), &(mylist.list));
    }
    printf("\n");
    printf("traversing the list using list_for_each()\n");


    list_for_each(pos, &mylist.list){
        tmp = list_entry(pos, struct kool_list, list);
        printf("to= %d from= %d\n", tmp->to, tmp->from);
    }

    printf("\n");
    printf("traversing the list using list_for_each_entry()\n");


    list_for_each_entry(tmp, &mylist.list, list){
   printf("to= %d from= %d\n", tmp->to, tmp->from);
    }
    printf("\n");
 
    printf("deleting the list using list_for_each_safe()\n");


    list_for_each_safe(pos, q, &mylist.list){
        tmp= list_entry(pos,struct kool_list, list);
        printf("freeing item to= %d from= %d\n", tmp->to, tmp->from);
        list_del(pos);
        free(tmp);
    }


    return 0;
}

===========================运行结果===========================

enter to and from:1 2
enter to and from:3 4
enter to and from:5 6 


traversing the list using list_for_each()
to= 5 from= 6
to= 3 from= 4
to= 1 from= 2


traversing the list using list_for_each_entry()
to= 5 from= 6
to= 3 from= 4
to= 1 from= 2


deleting the list using list_for_each_safe()
freeing item to= 5 from= 6
freeing item to= 3 from= 4
freeing item to= 1 from= 2