Re: [PATCH] list.h: add list_for_each_struct_entry macro
From: Jiri Pirko
Date: Mon Jan 18 2010 - 16:07:36 EST
Mon, Jan 18, 2010 at 06:17:13PM CET, bhutchings@xxxxxxxxxxxxxx wrote:
>On Mon, 2010-01-18 at 17:23 +0100, Jiri Pirko wrote:
>> When preparing to upcoming migration of mc_list (list of multicast MACs)
>> to list_head, the need of traversing the list over one structure member
>> appeared. I thought I'll do it locally but I decided that an intruduction
>> the macro in list.h would be much clearer. Please kindly for a review.
>> Signed-off-by: Jiri Pirko <jpirko@xxxxxxxxxx>
>> diff --git a/include/linux/list.h b/include/linux/list.h
>> index 969f6e9..8350a94 100644
>> --- a/include/linux/list.h
>> +++ b/include/linux/list.h
>> @@ -420,6 +420,22 @@ static inline void list_splice_tail_init(struct list_head *list,
>> pos = list_entry(pos->member.prev, typeof(*pos), member))
>> + * list_for_each_struct_entry - iterate over list of given type using
>> + * the struct member.
>> + * @pos: the type * to use as a loop cursor.
>> + * @head: the head for your list.
>> + * @type: the type of the struct.
>> + * @posmember: the name ot the loop cursor within the struct.
>> + * @member: the name of the list_struct within the struct.
>> + */
>> +#define list_for_each_struct_entry(pos, head, type, posmember, member) \
>> + for (pos = list_entry((head)->next, type, member)->posmember; \
>Surely &list_entry(...)->posmember ?
Ugh, right, I tested this with char * so it worked well. Got i corrected now so
I can repost.
>> + prefetch(container_of(pos, type, posmember)->member.next), \
>> + &container_of(pos, type, posmember)->member != (head); \
>It seems a bit dodgy to do this pointer arithmetic on a list node which
>might be the list head.
Well I tried to be as much close to other traverse macros as it could be.
>> + pos = list_entry(container_of(pos, type, posmember)->member.next, \
>> + type, member)->posmember)
>#define list_for_each_struct_entry(pos, head, type, posmember, member) \
> for (pos = list_empty(head) ? NULL : \
> &list_first_entry(head, type, member)->posmember; \
> prefetch(container_of(pos, type, posmember)->member.next), pos; \
> pos = list_is_last(&container_of(pos, type, posmember)->member, \
> head) ? NULL : \
> &list_entry(container_of(pos, type, posmember)->member.next, \
> type, member)->posmember)
At the first glance, this would take even more cputime for lists longer
than 2 or so, wouldn't it?
>Ben Hutchings, Senior Software Engineer, Solarflare Communications
>Not speaking for my employer; that's the marketing department's job.
>They asked us to note that Solarflare product names are trademarked.
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