RCU, rculist.h: fix list iterators

RCU list iterators: should prefetch ever be optimised out with no
side-effects, the current version will lose the barrier completely.

Pointed-out-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/rculist.h

@@ -180,31 +180,14 @@ static inline void list_splice_init_rcu(struct list_head *list,
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define list_for_each_rcu(pos, head) \
-	for (pos = (head)->next; \
+	for (pos = rcu_dereference((head)->next); \
-		prefetch(rcu_dereference(pos)->next), pos != (head); \
+		prefetch(pos->next), pos != (head); \
-		pos = pos->next)
+		pos = rcu_dereference(pos->next))
 
 #define __list_for_each_rcu(pos, head) \
-	for (pos = (head)->next; \
+	for (pos = rcu_dereference((head)->next); \
-		rcu_dereference(pos) != (head); \
+		pos != (head); \
-		pos = pos->next)
+		pos = rcu_dereference(pos->next))
-
-/**
- * list_for_each_safe_rcu
- * @pos:	the &struct list_head to use as a loop cursor.
- * @n:		another &struct list_head to use as temporary storage
- * @head:	the head for your list.
- *
- * Iterate over an rcu-protected list, safe against removal of list entry.
- *
- * 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_safe_rcu(pos, n, head) \
-	for (pos = (head)->next; \
-		n = rcu_dereference(pos)->next, pos != (head); \
-		pos = n)
 
 /**
  * list_for_each_entry_rcu	-	iterate over rcu list of given type
@@ -217,10 +200,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define list_for_each_entry_rcu(pos, head, member) \
-	for (pos = list_entry((head)->next, typeof(*pos), member); \
+	for (pos = list_entry(rcu_dereference((head)->next), typeof(*pos), member); \
-		prefetch(rcu_dereference(pos)->member.next), \
+		prefetch(pos->member.next), &pos->member != (head); \
-			&pos->member != (head); \
+		pos = list_entry(rcu_dereference(pos->member.next), typeof(*pos), member))
-		pos = list_entry(pos->member.next, typeof(*pos), member))
 
 
 /**
@@ -235,9 +217,9 @@ static inline void list_splice_init_rcu(struct list_head *list,
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define list_for_each_continue_rcu(pos, head) \
-	for ((pos) = (pos)->next; \
+	for ((pos) = rcu_dereference((pos)->next); \
-		prefetch(rcu_dereference((pos))->next), (pos) != (head); \
+		prefetch((pos)->next), (pos) != (head); \
-		(pos) = (pos)->next)
+		(pos) = rcu_dereference((pos)->next))
 
 /**
  * hlist_del_rcu - deletes entry from hash list without re-initialization
@@ -382,10 +364,10 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev,
  * as long as the traversal is guarded by rcu_read_lock().
  */
 #define hlist_for_each_entry_rcu(tpos, pos, head, member)		 \
-	for (pos = (head)->first;					 \
+	for (pos = rcu_dereference((head)->first);			 \
-	     rcu_dereference(pos) && ({ prefetch(pos->next); 1; }) &&	 \
+		pos && ({ prefetch(pos->next); 1; }) &&			 \
 		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
-	     pos = pos->next)
+		pos = rcu_dereference(pos->next))
 
 #endif	/* __KERNEL__ */
 #endif