list_for_each_safe和list_for_each_entry的区别
时间: 2023-06-05 08:05:20 浏览: 495
list_for_each_safe和list_for_each_entry是Linux内核中遍历链表的两种方法。它们的区别在于,list_for_each_safe可以删除当前遍历到的节点的下一个节点;而list_for_each_entry则可以根据链表节点中的成员偏移量,获取链表节点结构体的指针。这两种方法都比较常用,具体使用哪种方法取决于具体的需求。
相关问题
list_for_each_entry_safe代码解读
list_for_each_entry_safe是Linux内核中的一个宏,用于遍历双向链表。它与list_for_each_entry的区别在于,它增加了一个指针n对链表的下一个数据结构进行临时存储,所以在遍历链表的时候如果需要做删除链表的操作,使用list_for_each_entry_safe可以安全的删除,不会影响后续的遍历过程。
下面是一个list_for_each_entry_safe的示例代码:
```c
struct list_head *pos, *n;
struct my_struct *entry;
list_for_each_entry_safe(entry, pos, n, &my_list) {
// 对entry进行操作
// ...
// 删除entry
list_del(&entry->list);
// ...
}
```
在上面的代码中,my_list是一个双向链表,entry是链表中的一个元素,包含一个名为list的list_head结构体,用于连接链表。pos和n是两个指向list_head结构体的指针,用于遍历链表。在遍历链表的过程中,如果需要删除链表中的元素,可以使用list_del函数,它会将元素从链表中删除,并将元素的list_head结构体的指针置为NULL,这样就不会影响后续的遍历过程。
list_for_each_entry_safe_reverse
list_for_each_entry_safe_reverse is a macro in the Linux kernel that is used to iterate over a doubly linked list in reverse order, while safely removing or modifying the entries in the list.
The macro takes four arguments:
1. pointer to the current entry in the list
2. pointer to the temporary variable used to store the next entry
3. pointer to the head of the list
4. name of the member in the struct that represents the list
Here is the syntax for the macro:
```
list_for_each_entry_safe_reverse(pos, n, head, member) {
// do something with pos
}
```
The macro works by iterating over the list in reverse order, starting from the last entry and moving towards the head of the list. It uses a temporary variable (n) to store the next entry before modifying or removing the current entry (pos). This ensures that the list remains intact while the iteration is in progress.
Overall, list_for_each_entry_safe_reverse is a useful macro for safely iterating over and modifying doubly linked lists in the Linux kernel.