summaryrefslogtreecommitdiff
path: root/include
diff options
context:
space:
mode:
authorTom Rini <trini@konsulko.com>2025-06-18 08:05:29 -0600
committerTom Rini <trini@konsulko.com>2025-06-18 08:05:29 -0600
commitce2a7fcbd565d55b1d3fdc0e68edd50a21eca7d4 (patch)
tree857f80e55d97e4170a71a02f90972f95522a6e21 /include
parent5d7e003248ae836cbcc2b4c254901c1d85c85537 (diff)
parent1d19bbcb68280814952bdc18d7dec6d083b2c0ef (diff)
Merge patch series "list.h/treewide: get rid of no-op prefetch()"
Rasmus Villemoes <ravi@prevas.dk> says: While looking through list.h, I saw that the regular list_* helpers (and one of the hlist_* ones) still contain the prefetch() that was removed in linux 14 years ago. It doesn't do anything, but makes the macros harder to read, so get rid of it, and the fallback, no-op definition that they relied on. That requires removing a few uses outside list.h as well. checkpatch warns about some whitespace issues in list.h, but as I've copied whole kerneldoc+#define blocks directly from the linux kernel, I think it's better to just accept that so that we don't introduce needless diffs. The "macro argument reuse" arguments should also be ignored, as e.g. the "member" arguments are obviously always just bare identifiers, and the "pos" arguments must be assigned to multiple times. Link: https://lore.kernel.org/r/20250507121246.518691-1-ravi@prevas.dk
Diffstat (limited to 'include')
-rw-r--r--include/linux/list.h104
1 files changed, 59 insertions, 45 deletions
diff --git a/include/linux/list.h b/include/linux/list.h
index 0f9d939b05f..3dc38279716 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -4,11 +4,6 @@
#include <linux/stddef.h>
#include <linux/poison.h>
-#ifndef ARCH_HAS_PREFETCH
-#define ARCH_HAS_PREFETCH
-static inline void prefetch(const void *x) {;}
-#endif
-
/*
* Simple doubly linked list implementation.
*
@@ -170,6 +165,16 @@ static inline int list_is_last(const struct list_head *list,
}
/**
+ * 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 +368,28 @@ 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 +397,7 @@ 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 +417,39 @@ 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 +466,41 @@ 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 +669,7 @@ 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; }); \