---

yaml
---
r: 202966
b: refs/heads/master
c: 5f2f892
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: d5f31fbfd8fa3836a918592032853c41d1797c3d
+refs/heads/master: 5f2f89209500623ccb4713ec4af7de86fd30a9e4

trunk/net/ipv4/inetpeer.c

@@ -187,7 +187,12 @@ static struct inet_peer *lookup_rcu_bh(__be32 daddr)
 
 	while (u != peer_avl_empty) {
 		if (daddr == u->v4daddr) {
-			if (unlikely(!atomic_inc_not_zero(&u->refcnt)))
+			/* Before taking a reference, check if this entry was
+			 * deleted, unlink_from_pool() sets refcnt=-1 to make
+			 * distinction between an unused entry (refcnt=0) and
+			 * a freed one.
+			 */
+			if (unlikely(!atomic_add_unless(&u->refcnt, 1, -1)))
 				u = NULL;
 			return u;
 		}
@@ -322,8 +327,9 @@ static void unlink_from_pool(struct inet_peer *p)
 	 * in cleanup() function to prevent sudden disappearing.  If we can
 	 * atomically (because of lockless readers) take this last reference,
 	 * it's safe to remove the node and free it later.
+	 * We use refcnt=-1 to alert lockless readers this entry is deleted.
 	 */
-	if (atomic_cmpxchg(&p->refcnt, 1, 0) == 1) {
+	if (atomic_cmpxchg(&p->refcnt, 1, -1) == 1) {
 		struct inet_peer **stack[PEER_MAXDEPTH];
 		struct inet_peer ***stackptr, ***delp;
 		if (lookup(p->v4daddr, stack) != p)