文章目录
- 一、RCU 模式下添加链表项 list_add_rcu 函数
- 二、RCU 模式下删除链表项 list_del_rcu 函数
一、RCU 模式下添加链表项 list_add_rcu 函数
在 Linux 源码 linux-5.6.18includelinuxrculist.h 头文件中定义的就是 RCU 链表的操作 ,
其中定义的
代码语言：javascript复制static inline void list_add_rcu(struct list_head *new, struct list_head *head)函数 , 就是 向 链表中 添加元素 的 函数 ;
list_add_rcu 函数中 , 主要是调用了 __list_add_rcu 函数 ,
在 __list_add_rcu 函数中 , 将新添加的 链表项 添加到了 struct list_head *prev 和 struct list_head *next 两个链表项的中间 ;
list_add_rcu 函数原型 :
代码语言：javascript复制/*
* 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)
{
if (!__list_add_valid(new, prev, next))
return;
new->next = next;
new->prev = prev;
rcu_assign_pointer(list_next_rcu(prev), new);
next->prev = 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);
}
源码路径 : linux-5.6.18includelinuxrculist.h#105
二、RCU 模式下删除链表项 list_del_rcu 函数
在 Linux 源码 linux-5.6.18includelinuxrculist.h 头文件中定义的就是 RCU 链表的操作 ,
其中定义的
代码语言：javascript复制static inline void list_del_rcu(struct list_head *entry)函数 , 就是 从 链表中 删除元素 的 函数 ;
list_del_rcu 函数中 , 主要是调用了 __list_del_entry 函数 ,
在 __list_del_entry 函数中 , 又调用了 __list_del 函数 ;
list_del_rcu 函数原型 :
代码语言：javascript复制/**
* 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(entry);
entry->prev = LIST_POISON2;
}
static inline void __list_del_entry(struct list_head *entry)
{
if (!__list_del_entry_valid(entry))
return;
__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(entry);
entry->next = LIST_POISON1;
entry->prev = LIST_POISON2;
}
源码路径 : linux-5.6.18includelinuxrculist.h#156
