Just pointing out that these lists are circular. Back in the old days we used to call them “rings”.

 

From list.h:

 

183 /**

184  * list_empty - tests whether a list is empty

185  * @head: the list to test.

186  */

187 static inline int list_empty(const struct list_head *head)

188 {

189         return head->next == head;

  190 }

 

Jeff Haran