1 files changed, 62 insertions, 5 deletions

diff --git a/include/linux/list.h b/include/linux/list.h
index 611059d633f..f9d71eab05e 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))