-----Original Message----- From: kernelnewbies-bounces@xxxxxxxxxxxxxxxxx [mailto:kernelnewbies-bounces@xxxxxxxxxxxxxxxxx] On Behalf Of Leandro M Barbosa Sent: Wednesday, March 25, 2015 2:41 PM To: kernelnewbies@xxxxxxxxxxxxxxxxx Subject: Re: Kernel Linked Lists (list_splice) To clarify my doubt, it seems to me that it just sits there in memory without it being referenced anymore, is that right? On Wed, Mar 25, 2015 at 6:38 PM, Leandro M Barbosa <lbarbosa@xxxxxxxxx> wrote: > Hello all! > > I was reading the __list_splice () function code and I had a doubt. The code is: > > 274 static inline void __list_splice(const struct list_head *list, > 275 struct list_head *prev, > 276 struct list_head *next) > 277 { > 278 struct list_head *first = list->next; > 279 struct list_head *last = list->prev; > 280 > 281 first->prev = prev; > 282 prev->next = first; > 283 > 284 last->next = next; > 285 next->prev = last; > 286 } > > What happens with the *list head? As I understood, when you call > list_splice (list_a, list_b, list_b->next), the code joins the two > lists together such that the list_a is put before list_b. The code > grabs list->next and list->prev but what about *list itself? > > > -- > Leandro Moreira Barbosa The linked list API represented in list.h allows the creation of linked lists in which a list of structures containing instances of struct list_head can be linked together and anchored by an instance of a struct list_head which is not a member of the structures in the list. Sometimes that anchor is a standalone instance of struct list_head. Other times it's an instance of list_head in another structure, for example: struct foo { int data; struct list_head list; }; struct bar { int other_data; struct list_head foo_list; }; With the above you'd create a linked list of struct foos that is anchored (or headed) by the foo_list field in an instance of struct bar. That means that when you splice the list of foos in one instance of bar A to the list of foos in another instance of bar B, you don't want to include the foo_list in the A in the list in B since it's not contained in a foo, but another bar. This is different than the traditional linked lists that they taught me back in the stone age when I took CS101, but it enables a single object to be included in many lists. Jeff Haran _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
