From c6fe44d96fc1536af5b11cd859686453d1b7bfd1 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Thu, 23 Jul 2020 12:33:41 -0700 Subject: list: add "list_del_init_careful()" to go with "list_empty_careful()" That gives us ordering guarantees around the pair. Signed-off-by: Linus Torvalds --- include/linux/list.h | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) (limited to 'include/linux/list.h') diff --git a/include/linux/list.h b/include/linux/list.h index aff44d34f4e4..0d0d17a10d25 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -282,6 +282,24 @@ static inline int list_empty(const struct list_head *head) return READ_ONCE(head->next) == head; } +/** + * list_del_init_careful - deletes entry from list and reinitialize it. + * @entry: the element to delete from the list. + * + * This is the same as list_del_init(), except designed to be used + * together with list_empty_careful() in a way to guarantee ordering + * of other memory operations. + * + * Any memory operations done before a list_del_init_careful() are + * guaranteed to be visible after a list_empty_careful() test. + */ +static inline void list_del_init_careful(struct list_head *entry) +{ + __list_del_entry(entry); + entry->prev = entry; + smp_store_release(&entry->next, entry); +} + /** * list_empty_careful - tests whether a list is empty and not being modified * @head: the list to test @@ -297,7 +315,7 @@ static inline int list_empty(const struct list_head *head) */ static inline int list_empty_careful(const struct list_head *head) { - struct list_head *next = head->next; + struct list_head *next = smp_load_acquire(&head->next); return (next == head) && (next == head->prev); } -- cgit v1.2.3