diff options
Diffstat (limited to 'include/linux/list.h')
| -rw-r--r-- | include/linux/list.h | 67 |
1 files changed, 62 insertions, 5 deletions
diff --git a/include/linux/list.h b/include/linux/list.h index 611059d633f4..f9d71eab05ee 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -161,7 +161,7 @@ static inline void __list_del(struct list_head * prev, struct list_head * next) /** * list_del - deletes entry from list. * @entry: the element to delete from the list. - * Note: list_empty on entry does not return true after this, the entry is + * Note: list_empty() on entry does not return true after this, the entry is * in an undefined state. */ #ifndef CONFIG_DEBUG_LIST @@ -179,7 +179,7 @@ extern void list_del(struct list_head *entry); * list_del_rcu - deletes entry from list without re-initialization * @entry: the element to delete from the list. * - * Note: list_empty on entry does not return true after this, + * Note: list_empty() on entry does not return true after this, * the entry is in an undefined state. It is useful for RCU based * lockfree traversal. * @@ -209,7 +209,8 @@ static inline void list_del_rcu(struct list_head *entry) * list_replace - replace old entry by new one * @old : the element to be replaced * @new : the new element to insert - * Note: if 'old' was empty, it will be overwritten. + * + * If @old was empty, it will be overwritten. */ static inline void list_replace(struct list_head *old, struct list_head *new) @@ -360,6 +361,62 @@ static inline void list_splice_init(struct list_head *list, } /** + * list_splice_init_rcu - splice an RCU-protected list into an existing list. + * @list: the RCU-protected list to splice + * @head: the place in the list to splice the first list into + * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ... + * + * @head can be RCU-read traversed concurrently with this function. + * + * Note that this function blocks. + * + * Important note: the caller must take whatever action is necessary to + * prevent any other updates to @head. In principle, it is possible + * to modify the list as soon as sync() begins execution. + * If this sort of thing becomes necessary, an alternative version + * based on call_rcu() could be created. But only if -really- + * needed -- there is no shortage of RCU API members. + */ +static inline void list_splice_init_rcu(struct list_head *list, + struct list_head *head, + void (*sync)(void)) +{ + struct list_head *first = list->next; + struct list_head *last = list->prev; + struct list_head *at = head->next; + + if (list_empty(head)) + return; + + /* "first" and "last" tracking list, so initialize it. */ + + INIT_LIST_HEAD(list); + + /* + * At this point, the list body still points to the source list. + * Wait for any readers to finish using the list before splicing + * the list body into the new list. Any new readers will see + * an empty list. + */ + + sync(); + + /* + * Readers are finished with the source list, so perform splice. + * The order is important if the new list is global and accessible + * to concurrent RCU readers. Note that RCU readers are not + * permitted to traverse the prev pointers without excluding + * this function. + */ + + last->next = at; + smp_wmb(); + head->next = first; + first->prev = head; + at->prev = last; +} + +/** * list_entry - get the struct for this entry * @ptr: the &struct list_head pointer. * @type: the type of the struct this is embedded in. @@ -432,12 +489,12 @@ static inline void list_splice_init(struct list_head *list, pos = list_entry(pos->member.prev, typeof(*pos), member)) /** - * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue + * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue() * @pos: the type * to use as a start point * @head: the head of the list * @member: the name of the list_struct within the struct. * - * Prepares a pos entry for use as a start point in list_for_each_entry_continue. + * Prepares a pos entry for use as a start point in list_for_each_entry_continue(). */ #define list_prepare_entry(pos, head, member) \ ((pos) ? : list_entry(head, typeof(*pos), member)) |