From c1c2b5c6a4c09fe57933b70ec6289795f732ac83 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Wed, 7 May 2025 14:12:43 +0200 Subject: [PATCH] linux/list.h: drop use of prefetch() The use of prefetch() in these list helpers was dropped back in 2011 in linux (e66eed651fd1 ("list: remove prefetching from regular list iterators")). No arch in U-Boot defines any actual prefetch(), and as the referenced commit says, it's usually not a win anyway. Whole-sale sync of list.h is not really feasible, but we can synchronize the macros containing a prefetch() with their linux implementations as of v6.15-rc5, also importing the various helpers needed, e.g. list_is_head() and list_next_entry(). Signed-off-by: Rasmus Villemoes --- include/linux/list.h | 99 ++++++++++++++++++++++++++------------------ 1 file changed, 59 insertions(+), 40 deletions(-) diff --git a/include/linux/list.h b/include/linux/list.h index 0f9d939b05f..e21ae03b208 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -169,6 +169,16 @@ static inline int list_is_last(const struct list_head *list, return list->next == head; } +/** + * list_is_head - tests whether @list is the list @head + * @list: the entry to test + * @head: the head of the list + */ +static inline int list_is_head(const struct list_head *list, const struct list_head *head) +{ + return list == head; +} + /** * list_empty - tests whether a list is empty * @head: the list to test. @@ -363,26 +373,28 @@ static inline void list_splice_tail_init(struct list_head *list, }) /** - * list_for_each - iterate over a list - * @pos: the &struct list_head to use as a loop cursor. - * @head: the head for your list. + * list_next_entry - get the next element in list + * @pos: the type * to cursor + * @member: the name of the list_head within the struct. */ -#define list_for_each(pos, head) \ - for (pos = (head)->next; prefetch(pos->next), pos != (head); \ - pos = pos->next) +#define list_next_entry(pos, member) \ + list_entry((pos)->member.next, typeof(*(pos)), member) + +/** + * list_prev_entry - get the prev element in list + * @pos: the type * to cursor + * @member: the name of the list_head within the struct. + */ +#define list_prev_entry(pos, member) \ + list_entry((pos)->member.prev, typeof(*(pos)), member) /** - * __list_for_each - iterate over a list + * list_for_each - iterate over a list * @pos: the &struct list_head to use as a loop cursor. * @head: the head for your list. - * - * This variant differs from list_for_each() in that it's the - * simplest possible list iteration code, no prefetching is done. - * Use this for code that knows the list to be very short (empty - * or 1 entry) most of the time. */ -#define __list_for_each(pos, head) \ - for (pos = (head)->next; pos != (head); pos = pos->next) +#define list_for_each(pos, head) \ + for (pos = (head)->next; !list_is_head(pos, (head)); pos = pos->next) /** * list_for_each_prev - iterate over a list backwards @@ -390,8 +402,7 @@ static inline void list_splice_tail_init(struct list_head *list, * @head: the head for your list. */ #define list_for_each_prev(pos, head) \ - for (pos = (head)->prev; prefetch(pos->prev), pos != (head); \ - pos = pos->prev) + for (pos = (head)->prev; !list_is_head(pos, (head)); pos = pos->prev) /** * list_for_each_safe - iterate over a list safe against removal of list entry @@ -411,30 +422,39 @@ static inline void list_splice_tail_init(struct list_head *list, */ #define list_for_each_prev_safe(pos, n, head) \ for (pos = (head)->prev, n = pos->prev; \ - prefetch(pos->prev), pos != (head); \ + !list_is_head(pos, (head)); \ pos = n, n = pos->prev) +/** + * list_entry_is_head - test if the entry points to the head of the list + * @pos: the type * to cursor + * @head: the head for your list. + * @member: the name of the list_head within the struct. + */ +#define list_entry_is_head(pos, head, member) \ + list_is_head(&pos->member, (head)) + /** * list_for_each_entry - iterate over list of given type * @pos: the type * to use as a loop cursor. * @head: the head for your list. - * @member: the name of the list_struct within the struct. + * @member: the name of the list_head within the struct. */ #define list_for_each_entry(pos, head, member) \ - for (pos = list_entry((head)->next, typeof(*pos), member); \ - prefetch(pos->member.next), &pos->member != (head); \ - pos = list_entry(pos->member.next, typeof(*pos), member)) + for (pos = list_first_entry(head, typeof(*pos), member); \ + !list_entry_is_head(pos, head, member); \ + pos = list_next_entry(pos, member)) /** * list_for_each_entry_reverse - iterate backwards over list of given type. * @pos: the type * to use as a loop cursor. * @head: the head for your list. - * @member: the name of the list_struct within the struct. + * @member: the name of the list_head within the struct. */ #define list_for_each_entry_reverse(pos, head, member) \ - for (pos = list_entry((head)->prev, typeof(*pos), member); \ - prefetch(pos->member.prev), &pos->member != (head); \ - pos = list_entry(pos->member.prev, typeof(*pos), member)) + for (pos = list_last_entry(head, typeof(*pos), member); \ + !list_entry_is_head(pos, head, member); \ + pos = list_prev_entry(pos, member)) /** * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue() @@ -451,41 +471,41 @@ static inline void list_splice_tail_init(struct list_head *list, * list_for_each_entry_continue - continue iteration over list of given type * @pos: the type * to use as a loop cursor. * @head: the head for your list. - * @member: the name of the list_struct within the struct. + * @member: the name of the list_head within the struct. * * Continue to iterate over list of given type, continuing after * the current position. */ -#define list_for_each_entry_continue(pos, head, member) \ - for (pos = list_entry(pos->member.next, typeof(*pos), member); \ - prefetch(pos->member.next), &pos->member != (head); \ - pos = list_entry(pos->member.next, typeof(*pos), member)) +#define list_for_each_entry_continue(pos, head, member) \ + for (pos = list_next_entry(pos, member); \ + !list_entry_is_head(pos, head, member); \ + pos = list_next_entry(pos, member)) /** * list_for_each_entry_continue_reverse - iterate backwards from the given point * @pos: the type * to use as a loop cursor. * @head: the head for your list. - * @member: the name of the list_struct within the struct. + * @member: the name of the list_head within the struct. * * Start to iterate over list of given type backwards, continuing after * the current position. */ #define list_for_each_entry_continue_reverse(pos, head, member) \ - for (pos = list_entry(pos->member.prev, typeof(*pos), member); \ - prefetch(pos->member.prev), &pos->member != (head); \ - pos = list_entry(pos->member.prev, typeof(*pos), member)) + for (pos = list_prev_entry(pos, member); \ + !list_entry_is_head(pos, head, member); \ + pos = list_prev_entry(pos, member)) /** * list_for_each_entry_from - iterate over list of given type from the current point * @pos: the type * to use as a loop cursor. * @head: the head for your list. - * @member: the name of the list_struct within the struct. + * @member: the name of the list_head within the struct. * * Iterate over list of given type, continuing from current position. */ -#define list_for_each_entry_from(pos, head, member) \ - for (; prefetch(pos->member.next), &pos->member != (head); \ - pos = list_entry(pos->member.next, typeof(*pos), member)) +#define list_for_each_entry_from(pos, head, member) \ + for (; !list_entry_is_head(pos, head, member); \ + pos = list_next_entry(pos, member)) /** * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry @@ -654,8 +674,7 @@ static inline void hlist_add_after(struct hlist_node *n, #define hlist_entry(ptr, type, member) container_of(ptr,type,member) #define hlist_for_each(pos, head) \ - for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \ - pos = pos->next) + for (pos = (head)->first; pos ; pos = pos->next) #define hlist_for_each_safe(pos, n, head) \ for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \ -- 2.47.2