rculist: Improve documentation for list_for_each_entry_from_rcu()

Unfortunately the patch for adding list_for_each_entry_from_rcu() wasn't the final patch after all review. It is functionally correct but the documentation was incomplete. This patch adds this missing documentation which includes an update to the documentation for list_for_each_entry_continue_rcu() to match the documentation for the new list_for_each_entry_from_rcu(), and adds list_for_each_entry_from_rcu() and the already existing hlist_for_each_entry_from_rcu() to section 7 of whatisRCU.txt. Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
thallett · Jul 12, 2018 · b7b6f94 · b7b6f94
1 parent 52e17ba
commit b7b6f94
Show file tree

Hide file tree

Showing 2 changed files with 20 additions and 1 deletion.
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
@@ -820,11 +820,13 @@ RCU list traversal:
 	list_next_rcu
 	list_for_each_entry_rcu
 	list_for_each_entry_continue_rcu
+	list_for_each_entry_from_rcu
 	hlist_first_rcu
 	hlist_next_rcu
 	hlist_pprev_rcu
 	hlist_for_each_entry_rcu
 	hlist_for_each_entry_rcu_bh
+	hlist_for_each_entry_from_rcu
 	hlist_for_each_entry_continue_rcu
 	hlist_for_each_entry_continue_rcu_bh
 	hlist_nulls_first_rcu

diff --git a/include/linux/rculist.h b/include/linux/rculist.h
@@ -396,7 +396,16 @@ static inline void list_splice_tail_init_rcu(struct list_head *list,
  * @member:	the name of the list_head within the struct.
  *
  * Continue to iterate over list of given type, continuing after
- * the current position.
+ * the current position which must have been in the list when the RCU read
+ * lock was taken.
+ * This would typically require either that you obtained the node from a
+ * previous walk of the list in the same RCU read-side critical section, or
+ * that you held some sort of non-RCU reference (such as a reference count)
+ * to keep the node alive *and* in the list.
+ *
+ * This iterator is similar to list_for_each_entry_from_rcu() except
+ * this starts after the given position and that one starts at the given
+ * position.
  */
 #define list_for_each_entry_continue_rcu(pos, head, member) 		\
 	for (pos = list_entry_rcu(pos->member.next, typeof(*pos), member); \
@@ -411,6 +420,14 @@ static inline void list_splice_tail_init_rcu(struct list_head *list,
  *
  * Iterate over the tail of a list starting from a given position,
  * which must have been in the list when the RCU read lock was taken.
+ * This would typically require either that you obtained the node from a
+ * previous walk of the list in the same RCU read-side critical section, or
+ * that you held some sort of non-RCU reference (such as a reference count)
+ * to keep the node alive *and* in the list.
+ *
+ * This iterator is similar to list_for_each_entry_continue_rcu() except
+ * this starts from the given position and that one starts from the position
+ * after the given position.
  */
 #define list_for_each_entry_from_rcu(pos, head, member)			\
 	for (; &(pos)->member != (head);					\