处理链表:内核基本都是双向链表,其基本结构:
- struct list_head {
- struct list_head *next, *prev;
- };
xx/include/linux/list.h 文件记录了操作双向链表函数
初始化双向链表:1.用INIT_LIST_HEAD函数初始化一个双向链表
- static inline void INIT_LIST_HEAD(struct list_head *list)
- {
- list->next = list;
- list->prev = list;
- }
2.使用宏
创建并初始化一个双向链表
- #define LIST_HEAD_INIT(name) { &(name), &(name) }
- #define LIST_HEAD(name) \
- struct list_head name = LIST_HEAD_INIT(name)
还有其他链表操作函数,认真分析还是很容易搞定,在此不多介绍;
下面介绍下内核中经常会用到的(跟链表相关的)宏:1. list_entry: 与container_of功能相同;
- /**
- * 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)
2. list_for_each:向后(next)遍历head所指链表每个节点
- /**
- * 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)
3. list_for_each_prev:向前(prev)遍历head所指链表每个节点
- /**
- * 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)
4. list_for_each_entry:
- /**
- * 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))
注:关于typeof可见:
http://paullu.blog.51cto.com/828864/169145举个例子:
- struct kobject *k;
- list_for_each_entry(k, &kset->list, entry) {
- if (kobject_name(k) && !strcmp(kobject_name(k), name)) {
- ret = kobject_get(k);
- break;
- }
- //这是在kset_find_obj_hinted函数中使用的遍历kset中的kobject链表,寻找与name同名的kobject;
#####################################################################
接下来看看Klist,内核中使用的非常频繁,它是对list_head的扩展相关代码位于:xx/include/linux/klist.h,xx/lib/klist.c
- struct klist {
- spinlock_t k_lock;
- struct list_head k_list;
- void (*get)(struct klist_node *);
- void (*put)(struct klist_node *);
- } __attribute__ ((aligned (sizeof(void *)))); /* 按指针大小对齐 */
- struct klist_node {
- void *n_klist; /* never access directly */
- struct list_head n_node;
- struct kref n_ref;
- };
- struct klist_iter {
- struct klist *i_klist;
- struct klist_node *i_cur;
- };
待续。。。
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