From mboxrd@z Thu Jan  1 00:00:00 1970
From: navych@126.com (Navy Cheng)
Date: Fri, 4 Mar 2016 13:02:02 +0800
Subject: What is the role of LIST_POISON1 and LIST_POISON2?
Message-ID: <20160304050202.GA783@debian>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

Hi,

When I read the code of list_del(), I find LIST_POISON1 and LIST_POISON2:

    static inline void list_del(struct list_head *entry)
    {
	__list_del(entry->prev, entry->next);
	entry->next = LIST_POISON1;
	entry->prev = LIST_POISON2;
    }

Why not set entry->next and entry->prev to NULL ?

Thank you!