链表（list）使用注意

如下代码是linux上的链表接口源码，使用的这个链表（list）源码，可以方便快捷的建立链表队列，但使用时需要注意的坑有：
 1、不支持，多对多，否则在add的时候，因为要加入链表的对象只有一块list_head内存，如果将它多次添加到其他链表，那么只有最后一个有效，前面的均无效。
 2、如果链表节点的内存是动态申请的，在遍历链表的循环中，取得链表数据后要释放节点资源，必须使用list_for_each_entry_safe，不能使用list_for_each_entry
    否则将有访问异常风险，原因是：_safe才会将下一个节点先保存起来，当取得链表数据,释放完节点资源后，才能保证能查找到该节点后面的节点。

 #ifndef _LINUX_LIST_H_
 #define _LINUX_LIST_H_ 

 #ifdef __cplusplus
 extern "C" {
 #endif

 #include <stdbool.h>

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

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

 #define LIST_POISON1  ((void *) 0x00100100)
 #define LIST_POISON2  ((void *) 0x00200200) 

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

 /**
  * list_add - add a new entry
  * @new_entry: 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_entry, struct list_head *head)
 {
     __list_add(new_entry, head, head->next);
 } 

 /**
  * list_add_tail - add a new entry
  * @new_entry: 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_entry, struct list_head *head)
 {
     __list_add(new_entry, 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;
 } 

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

 /**
  * list_replace - replace old entry by new one
  * @old : the element to be replaced
  * @new_entry : 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_entry)
 {
     new_entry->next = old->next;
     new_entry->next->prev = new_entry;
     new_entry->prev = old->prev;
     new_entry->prev->next = new_entry;
 }

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

 /**
  * 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(entry);
     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_entry(list);
     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_entry(list);
     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_head within the struct.
  */
 #define list_entry(ptr, type, member) \
     container_of(ptr, type, 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_head 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_last_entry - get the last 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_head within the struct.
  *
  * Note, that list is expected to be not empty.
  */
 #define list_last_entry(ptr, type, member) \
     list_entry((ptr)->prev, 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_head 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_next_entry - get the next element in list
  * @pos:    the type * to cursor
  * @member:    the name of the list_head within the struct.
  */
 #define list_next_entry(pos, member) \
     list_entry((pos)->member.next, __typeof__(*(pos)), member)

 /**
  * list_prev_entry - get the prev element in list
  * @pos:    the type * to cursor
  * @member:    the name of the list_head within the struct.
  */
 #define list_prev_entry(pos, member) \
     list_entry((pos)->member.prev, __typeof__(*(pos)), 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; 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_head within the struct.
  */
 #define list_for_each_entry(pos, head, member) \
     for (pos = list_first_entry(head, __typeof__(*pos), member); \
          &pos->member != (head);                    \
          pos = list_next_entry(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_head within the struct.
  */
 #define list_for_each_entry_reverse(pos, head, member) \
     for (pos = list_last_entry(head, __typeof__(*pos), member); \
          &pos->member != (head); \
          pos = list_prev_entry(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_head 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_head 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_next_entry(pos, member); \
          &pos->member != (head); \
          pos = list_next_entry(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_head 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_prev_entry(pos, member); \
          &pos->member != (head); \
          pos = list_prev_entry(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_head 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_next_entry(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_head within the struct.
  */
 #define list_for_each_entry_safe(pos, n, head, member) \
     for (pos = list_first_entry(head, __typeof__(*pos), member), \
             n = list_next_entry(pos, member); \
          &pos->member != (head); \
          pos = n, n = list_next_entry(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_head 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_next_entry(pos, member), \
         n = list_next_entry(pos, member); \
          &pos->member != (head); \
          pos = n, n = list_next_entry(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_head 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_next_entry(pos, member); \
          &pos->member != (head); \
          pos = n, n = list_next_entry(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_head 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_last_entry(head, __typeof__(*pos), member), \
         n = list_prev_entry(pos, member); \
          &pos->member != (head); \
          pos = n, n = list_prev_entry(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_head 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_next_entry(pos, member)

 //HASH LIST
 struct hlist_head {
     struct hlist_node *first;
 }; 

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

 /*
  * 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).
  */
 #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 = (struct hlist_node *)LIST_POISON1;
     n->pprev = (struct hlist_node **)LIST_POISON2;
 } 

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

 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;
 } 

 /* 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_behind(struct hlist_node *n,
                     struct hlist_node *prev)
 {
     n->next = prev->next;
     prev->next = n;
     n->pprev = &prev->next;

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

 /* after that we'll appear to be on some hlist and hlist_del will work */
 static inline void hlist_add_fake(struct hlist_node *n)
 {
     n->pprev = &n->next;
 }

 static inline bool hlist_fake(struct hlist_node *h)
 {
     return h->pprev == &h->next;
 }

 /*
  * Check whether the node is the only node of the head without
  * accessing head:
  */
 static inline bool hlist_is_singular_node(struct hlist_node *n,
                                         struct hlist_head *h)
 {
     return !n->next && n->pprev == &h->first;
 }

 /*
  * Move a list from one list head to another. Fixup the pprev
  * reference of the first entry if it exists.
  */
 static inline void hlist_move_list(struct hlist_head *old,
                    struct hlist_head *new)
 {
     new->first = old->first;
     if (new->first)
         new->first->pprev = &new->first;
     old->first = NULL;
 }

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

 #define hlist_for_each(pos, head) \
     for (pos = (head)->first; pos ; pos = pos->next)

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

 #define hlist_entry_safe(ptr, type, member) \
     ({ __typeof__(ptr) ____ptr = (ptr); \
        ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
     })

 /**
  * hlist_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 hlist_node within the struct.
  */
 #define hlist_for_each_entry(pos, head, member) \
     for (pos = hlist_entry_safe((head)->first, __typeof__(*(pos)), member);\
          pos; \
          pos = hlist_entry_safe((pos)->member.next, __typeof__(*(pos)), member))

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

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

 /**
  * hlist_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 &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(pos, n, head, member) \
     for (pos = hlist_entry_safe((head)->first, __typeof__(*pos), member); \
          pos && ({ n = pos->member.next; ; });    \
          pos = hlist_entry_safe(n, __typeof__(*pos), member))

 #ifdef __cplusplus
 } /* extern "C" */
 #endif

 #endif