On 6/12/24 21:21, Keith Busch wrote:
From: Keith Busch kbusch@kernel.org
Provide a helper to remove elements from a list to the end, and place those elements in a new list.
Signed-off-by: Keith Busch kbusch@kernel.org
include/linux/list.h | 20 ++++++++++++++++++++ lib/list-test.c | 29 +++++++++++++++++++++++++++++ 2 files changed, 49 insertions(+)
diff --git a/include/linux/list.h b/include/linux/list.h index 5f4b0a39cf46a..f22850e854820 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -520,6 +520,26 @@ static inline void list_cut_before(struct list_head *list, entry->prev = head; } +/**
- list_cut - cut a list into two from the entry
- @list: a new list to add all removed entries
- @head: a list with entries
- @entry: an entry within head, could be the head itself
- This helper removes elements from @head starting at @entry until the end,
- and appends them to @lists.
- */
+static inline void list_cut(struct list_head *list,
struct list_head *head, struct list_head *entry)+{
- list->next = entry;
- list->prev = head->prev;
- head->prev = entry->prev;
- entry->prev->next = head;
- entry->prev = list;
- list->prev->next = list;
+}
I am wondering whether we really need the _rcu version of list_cut here? I think that @head could point to an _rcu protected list and that's true for this patch. So there might be concurrent readers accessing @head using _rcu list-traversal primitives, such as list_for_each_entry_rcu().
An _rcu version of list_cut():
static inline void list_cut_rcu(struct list_head *list, struct list_head *head, struct list_head *entry) { list->next = entry; list->prev = head->prev; head->prev = entry->prev; rcu_assign_pointer(list_next_rcu(entry->prev), head); entry->prev = list; list->prev->next = list; }
Thanks, --Nilay