@@ -118,6 +118,36 @@ static inline void list_del_rcu(struct list_head *entry)
}
/**
+ * list_del_bidir_rcu - deletes entry from list without re-initialization.
+ * Useful when one wants to perform bidirectional traversal of the list.
+ *
+ * @entry: the element to delete from the list.
+ *
+ * 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.
+ *
+ * In particular, since we should be able to traverse this list in both
+ * directions, it means that we can not poison either of the pointers
+ * (->prev and ->next) because they may still be used for walking the list.
+ *
+ * The caller must take whatever precautions are necessary (such as holding
+ * appropriate locks) to avoid racing with another list-mutation primitive,
+ * such as list_del_bidir_rcu() or list_add_rcu(), running on this same list.
+ * However, it is perfectly legal to run concurrently with the _rcu
+ * list-traversal primitives, such as list_for_each_entry_rcu() or
+ * list_for_each_entry_reverse_rcu().
+ *
+ * Note that the caller is not permitted to immediately free the newly deleted
+ * entry. Instead, either synchronize_rcu() or call_rcu() must be used to
+ * defer freeing until an RCU grace period has elapsed.
+ */
+static inline void list_del_bidir_rcu(struct list_head *entry)
+{
+ __list_del_entry(entry);
+}
+
+/**
* hlist_del_init_rcu - deletes entry from hash list with re-initialization
* @n: the element to delete from the hash list.
*
@@ -286,6 +316,22 @@ static inline void list_splice_init_rcu(struct list_head *list,
&pos->member != (head); \
pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
+/**
+ * list_for_each_entry_reverse_rcu - iterate backwards over rcu 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.
+ *
+ * This list-traversal primitive may safely run concurrently with
+ * the _rcu list-mutation primitives such as list_add_rcu()
+ * as long as the traversal is guarded by rcu_read_lock().
+ */
+#define list_for_each_entry_reverse_rcu(pos, head, member) \
+ for (pos = list_entry_rcu((head)->prev, typeof(*pos), member); \
+ &pos->member != (head); \
+ pos = list_entry_rcu(pos->member.prev, typeof(*pos), member))
/**
* list_for_each_continue_rcu
Provide a helper to traverse an RCU-protected doubly linked list in the reverse order. Also add a corresponding helper to delete entries from the linked list, which takes care to see that we don't poison either of the pointers (->prev and ->next), since it is legal to run an rcu list-traversal operation (in either forward/reverse direction) concurrently. Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> --- include/linux/rculist.h | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 46 insertions(+), 0 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html