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Github: __list_del_entry

Email: BuddyZhang1 buddy.zhang@aliyun.com

目录


源码分析

/**
 * 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_entry(struct list_head *entry)
{
        if (!__list_del_entry_valid(entry))
                return;

        __list_del(entry->prev, entry->next);
}

函数 __list_del_entry() 用于将一个节点从链表中删除。函数通过传入这个节点的指针,然后 调用 __list_del_entry_valid() 函数检查这个节点是否有效。如果无效,则返回;如果有效 则调用 __list_del() 函数将这个节点删除。

__list_del_entry_valid

__list_del_entry_valid

__list_del

__list_del


实践

驱动源码

/*
 * bindirect-list
 *
 * (C) 20179.04.25 <buddy.zhang@aliyun.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

/*
 * bidirect-list
 *
 * +-----------+<--o    +-----------+<--o    +-----------+<--o    +-----------+
 * |           |   |    |           |   |    |           |   |    |           |
 * |      prev |   o----| prev      |   o----| prev      |   o----| prev      |
 * | list_head |        | list_head |        | list_head |        | list_head |
 * |      next |---o    |      next |---o    |      next |---o    |      next |
 * |           |   |    |           |   |    |           |   |    |           |
 * +-----------+   o--->+-----------+   o--->+-----------+   o--->+-----------+
 *
 */

#include <linux/kernel.h>
#include <linux/init.h>

/* header of list */
#include <linux/list.h>

/* private structure */
struct node {
    const char *name;
    struct list_head list;
};

/* Initialize a group node structure */
static struct node node0 = { .name = "BiscuitOS_node0", };
static struct node node1 = { .name = "BiscuitOS_node1", };
static struct node node2 = { .name = "BiscuitOS_node2", };
static struct node node3 = { .name = "BiscuitOS_node3", };
static struct node node4 = { .name = "BiscuitOS_node4", };
static struct node node5 = { .name = "BiscuitOS_node5", };
static struct node node6 = { .name = "BiscuitOS_node6", };

/* Declaration and implement a bindirect-list */
LIST_HEAD(BiscuitOS_list);

static __init int bindirect_demo_init(void)
{
	struct node *np;

	/* add a new entry on special entry */
	list_add_tail(&node0.list, &BiscuitOS_list);
	list_add_tail(&node1.list, &BiscuitOS_list);
	list_add_tail(&node2.list, &BiscuitOS_list);
	list_add_tail(&node3.list, &BiscuitOS_list);
	list_add_tail(&node4.list, &BiscuitOS_list);
	list_add_tail(&node5.list, &BiscuitOS_list);
	list_add_tail(&node6.list, &BiscuitOS_list);

	/* Delete a entry */
	__list_del_entry(&node6.list);

	/* Traverser all node on bindirect-list */
	list_for_each_entry(np, &BiscuitOS_list, list)
		printk("%s\n", np->name);


	return 0;
}
device_initcall(bindirect_demo_init);

驱动安装

驱动的安装很简单,首先将驱动放到 drivers/BiscuitOS/ 目录下,命名为 list.c, 然后修改 Kconfig 文件,添加内容参考如下:

diff --git a/drivers/BiscuitOS/Kconfig b/drivers/BiscuitOS/Kconfig
index 4edc5a5..1a9abee 100644
--- a/drivers/BiscuitOS/Kconfig
+++ b/drivers/BiscuitOS/Kconfig
@@ -6,4 +6,14 @@ if BISCUITOS_DRV
config BISCUITOS_MISC
        bool "BiscuitOS misc driver"
+config BISCUITOS_LIST
+       bool "Bindirect-list"
+
+if BISCUITOS_LIST
+
+config DEBUG_BISCUITOS_LIST
+       bool "__list_del_entry"
+
+endif # BISCUITOS_LIST
+
endif # BISCUITOS_DRV

接着修改 Makefile,请参考如下修改:

diff --git a/drivers/BiscuitOS/Makefile b/drivers/BiscuitOS/Makefile
index 82004c9..9909149 100644
--- a/drivers/BiscuitOS/Makefile
+++ b/drivers/BiscuitOS/Makefile
@@ -1 +1,2 @@
obj-$(CONFIG_BISCUITOS_MISC)     += BiscuitOS_drv.o
+obj-$(CONFIG_BISCUITOS_LIST)    += list.o
--

驱动配置

驱动配置请参考下面文章中关于驱动配置一节。在配置中,勾选如下选项,如下:

Device Driver--->
    [*]BiscuitOS Driver--->
        [*]Bindirect-list
            [*]__list_del_entry()

具体过程请参考:

Linux 5.0 开发环境搭建 – 驱动配置

驱动编译

驱动编译也请参考下面文章关于驱动编译一节:

Linux 5.0 开发环境搭建 – 驱动编译

驱动运行

驱动的运行,请参考下面文章中关于驱动运行一节:

Linux 5.0 开发环境搭建 – 驱动运行

启动内核,并打印如下信息:

usbcore: registered new interface driver usbhid
usbhid: USB HID core driver
BiscuitOS_node0
BiscuitOS_node1
BiscuitOS_node2
BiscuitOS_node3
BiscuitOS_node4
BiscuitOS_node5
aaci-pl041 10004000.aaci: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 24
aaci-pl041 10004000.aaci: FIFO 512 entries

驱动分析

使用 __list_del_entry() 函数可以安全的删除一个节点。


附录

BiscuitOS Home

BiscuitOS Driver

BiscuitOS Kernel Build

Linux Kernel

Bootlin: Elixir Cross Referencer

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