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c linux-kernel pointers linked-list kernel-module

c - 如何在Linux内核中将链接列表的开头分配给指针?

发布于 2020-03-30 21:27:18

我正在为Linux内核编写程序,以实现链接列表并添加某些人的出生日期。添加它们之后,我需要找到最大使用期限并删除该节点。

为了找到具有最长使用期限的节点,我打算设置一个指向链表第一个元素的指针,并在进行迭代时比较使用期限。我不知道如何将最大指针设置为链接列表的开头。

我尝试了几种不同的方法,包括:

  • struct birthday * max = &birthday_list
  • struct birthday max = birthday_list
  • max = birthday_list.next;

错误我得到: error: assignment from incompatible pointer type [-Werror=incompatible-pointer-types]

我想我可能正在将列表分配给其他结构。我可以弄清楚我可能做错了什么吗?

#include<linux/list.h>
#include<linux/init.h>
#include<linux/kernel.h>
#include<linux/module.h>
#include<linux/types.h>
#include<linux/slab.h>

struct birthday {
    int day;
    int month;
    int year;
    struct list_head list;
}

static LIST_HEAD(birthday_list);
static void remove_oldest_student(void){
struct birthday *max, *curr, *next;
//point max to list head
max = LIST_HEAD(birthday_list);

list_for_each_entry(curr, &birthday_list, list){

  //find_max(&max, &curr);
}

    printk(KERN_INFO "Oldest Student Details --> Name: %s, Month: %d, Day: %d, Year: %d\n",max->name, max->month,max->day,max->year);
}


int simple_init(void) {
    struct birthday *ptr;
    int i;
    for(i = 0; i < 5; i++) {
        // create 5 birthday structs and add them to the list

        struct birthday *person;
        person = kmalloc(sizeof(*person), GFP_KERNEL);
        person->day = 22;
        person->month = 11;
        person->year = 1981;
        INIT_LIST_HEAD(&person->list);

        list_add_tail(&person->list, &birthday_list);
    }

    list_for_each_entry(ptr, &birthday_list, list) {
        // print the info from the structs to the log
        printk(KERN_INFO "%d, %d %d", ptr->month, ptr->day, ptr->year);
     }
remove_oldest_student();
    return 0;
    }


void simple_exit(void) {
    struct birthday *ptr, *next;
    list_for_each_entry_safe(ptr, next, &birthday_list, list) {
        // delete structs and return memory
        list_del(&ptr->list);
        kfree(ptr);
    }
}

module_init(simple_init);
module_exit(simple_exit);

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提问者
Dhruv
被浏览
59
Tsyvarev 2020-01-31 16:35

我打算设置一个指向链表第一个元素的指针

只需使用list_first_entry宏:

max = list_first_entry(&birthday_list, struct birthday, list);

提示:由于您已经有指向第一个元素的指针,因此无需在以下循环中对其进行迭代。代替list_for_each_entry您可以使用list_for_each_entry_continue

// Make iterator to point to the already located element (first element in the list)
curr = max;
// Continue iteration.
// So the first iterated element will be the second element in the list
list_for_each_entry_continue(curr, &birthday_list, list){

  //find_max(&max, &curr);
}