X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=rcuja%2Frcuja.c;h=9c90fdcdfc13b926c983e9be770aa5e51179e784;hb=46f373a6789943f3e64fd97e55cdb7a5234e50f2;hp=e6e3a3e6bcc5a10dcc6f0f24354ac5d2788c0573;hpb=fa1127990db461f839b1ffe2f3dea0ee2c45e89f;p=userspace-rcu.git

diff --git a/rcuja/rcuja.c b/rcuja/rcuja.c
index e6e3a3e..9c90fdc 100644
--- a/rcuja/rcuja.c
+++ b/rcuja/rcuja.c
@@ -277,6 +277,7 @@ static
 struct cds_ja_inode_flag *ja_linear_node_get_nth(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
 		struct cds_ja_inode_flag ***child_node_flag_ptr,
+		struct cds_ja_inode_flag **child_node_flag_v,
 		struct cds_ja_inode_flag ***node_flag_ptr,
 		uint8_t n)
 {
@@ -307,6 +308,8 @@ struct cds_ja_inode_flag *ja_linear_node_get_nth(const struct cds_ja_type *type,
 	ptr = rcu_dereference(pointers[i]);
 	if (caa_unlikely(child_node_flag_ptr) && ptr)
 		*child_node_flag_ptr = &pointers[i];
+	if (caa_unlikely(child_node_flag_v) && ptr)
+		*child_node_flag_v = ptr;
 	if (caa_unlikely(node_flag_ptr))
 		*node_flag_ptr = &pointers[i];
 	return ptr;
@@ -335,6 +338,7 @@ static
 struct cds_ja_inode_flag *ja_pool_node_get_nth(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
 		struct cds_ja_inode_flag ***child_node_flag_ptr,
+		struct cds_ja_inode_flag **child_node_flag_v,
 		struct cds_ja_inode_flag ***node_flag_ptr,
 		uint8_t n)
 {
@@ -348,7 +352,7 @@ struct cds_ja_inode_flag *ja_pool_node_get_nth(const struct cds_ja_type *type,
 	linear = (struct cds_ja_inode *)
 		&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
 	return ja_linear_node_get_nth(type, linear, child_node_flag_ptr,
-		node_flag_ptr, n);
+		child_node_flag_v, node_flag_ptr, n);
 }
 
 static
@@ -365,20 +369,25 @@ static
 struct cds_ja_inode_flag *ja_pigeon_node_get_nth(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
 		struct cds_ja_inode_flag ***child_node_flag_ptr,
+		struct cds_ja_inode_flag **child_node_flag_v,
 		struct cds_ja_inode_flag ***node_flag_ptr,
 		uint8_t n)
 {
 	struct cds_ja_inode_flag **child_node_flag;
+	struct cds_ja_inode_flag *child_node_flag_read;
 
 	assert(type->type_class == RCU_JA_PIGEON);
 	child_node_flag = &((struct cds_ja_inode_flag **) node->u.data)[n];
+	child_node_flag_read = rcu_dereference(*child_node_flag);
 	dbg_printf("ja_pigeon_node_get_nth child_node_flag_ptr %p\n",
 		child_node_flag);
-	if (caa_unlikely(child_node_flag_ptr) && *child_node_flag)
+	if (caa_unlikely(child_node_flag_ptr) && child_node_flag_read)
 		*child_node_flag_ptr = child_node_flag;
+	if (caa_unlikely(child_node_flag_v) && child_node_flag_read)
+		*child_node_flag_v = child_node_flag_read;
 	if (caa_unlikely(node_flag_ptr))
 		*node_flag_ptr = child_node_flag;
-	return rcu_dereference(*child_node_flag);
+	return child_node_flag_read;
 }
 
 static
@@ -386,7 +395,7 @@ struct cds_ja_inode_flag *ja_pigeon_node_get_ith_pos(const struct cds_ja_type *t
 		struct cds_ja_inode *node,
 		uint8_t i)
 {
-	return ja_pigeon_node_get_nth(type, node, NULL, NULL, i);
+	return ja_pigeon_node_get_nth(type, node, NULL, NULL, NULL, i);
 }
 
 /*
@@ -394,8 +403,9 @@ struct cds_ja_inode_flag *ja_pigeon_node_get_ith_pos(const struct cds_ja_type *t
  * node_flag is already rcu_dereference'd.
  */
 static
-struct cds_ja_inode_flag * ja_node_get_nth(struct cds_ja_inode_flag *node_flag,
+struct cds_ja_inode_flag *ja_node_get_nth(struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_inode_flag ***child_node_flag_ptr,
+		struct cds_ja_inode_flag **child_node_flag,
 		struct cds_ja_inode_flag ***node_flag_ptr,
 		uint8_t n)
 {
@@ -411,13 +421,16 @@ struct cds_ja_inode_flag * ja_node_get_nth(struct cds_ja_inode_flag *node_flag,
 	switch (type->type_class) {
 	case RCU_JA_LINEAR:
 		return ja_linear_node_get_nth(type, node,
-				child_node_flag_ptr, node_flag_ptr, n);
+				child_node_flag_ptr, child_node_flag,
+				node_flag_ptr, n);
 	case RCU_JA_POOL:
 		return ja_pool_node_get_nth(type, node,
-				child_node_flag_ptr, node_flag_ptr, n);
+				child_node_flag_ptr, child_node_flag,
+				node_flag_ptr, n);
 	case RCU_JA_PIGEON:
 		return ja_pigeon_node_get_nth(type, node,
-				child_node_flag_ptr, node_flag_ptr, n);
+				child_node_flag_ptr, child_node_flag,
+				node_flag_ptr, n);
 	default:
 		assert(0);
 		return (void *) -1UL;
@@ -950,7 +963,7 @@ struct cds_hlist_head cds_ja_lookup(struct cds_ja *ja, uint64_t key)
 		uint8_t iter_key;
 
 		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - i - 1)));
-		node_flag = ja_node_get_nth(node_flag, NULL, NULL,
+		node_flag = ja_node_get_nth(node_flag, NULL, NULL, NULL,
 			iter_key);
 		dbg_printf("cds_ja_lookup iter key lookup %u finds node_flag %p\n",
 				(unsigned int) iter_key, node_flag);
@@ -978,6 +991,7 @@ struct cds_hlist_head cds_ja_lookup(struct cds_ja *ja, uint64_t key)
 static
 int ja_attach_node(struct cds_ja *ja,
 		struct cds_ja_inode_flag **attach_node_flag_ptr,
+		struct cds_ja_inode_flag *attach_node_flag,
 		struct cds_ja_inode_flag **node_flag_ptr,
 		struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_inode_flag *parent_node_flag,
@@ -1015,9 +1029,20 @@ int ja_attach_node(struct cds_ja *ja,
 
 	if (node_flag_ptr && ja_node_ptr(*node_flag_ptr)) {
 		/*
-		 * Target node is non-NULL: it has been updated between
-		 * RCU lookup and lock acquisition. We need to re-try
-		 * lookup and attach.
+		 * Target node has been updated between RCU lookup and
+		 * lock acquisition. We need to re-try lookup and
+		 * attach.
+		 */
+		ret = -EAGAIN;
+		goto unlock_parent;
+	}
+
+	if (attach_node_flag_ptr && ja_node_ptr(*attach_node_flag_ptr) !=
+			ja_node_ptr(attach_node_flag)) {
+		/*
+		 * Target node has been updated between RCU lookup and
+		 * lock acquisition. We need to re-try lookup and
+		 * attach.
 		 */
 		ret = -EAGAIN;
 		goto unlock_parent;
@@ -1105,6 +1130,7 @@ static
 int ja_chain_node(struct cds_ja *ja,
 		struct cds_ja_inode_flag *parent_node_flag,
 		struct cds_ja_inode_flag **node_flag_ptr,
+		struct cds_ja_inode_flag *node_flag,
 		struct cds_hlist_head *head,
 		struct cds_ja_node *node)
 {
@@ -1115,7 +1141,7 @@ int ja_chain_node(struct cds_ja *ja,
 	if (!shadow_node) {
 		return -EAGAIN;
 	}
-	if (!ja_node_ptr(*node_flag_ptr)) {
+	if (ja_node_ptr(*node_flag_ptr) != ja_node_ptr(node_flag)) {
 		ret = -EAGAIN;
 		goto end;
 	}
@@ -1133,7 +1159,8 @@ int cds_ja_add(struct cds_ja *ja, uint64_t key,
 		**node_flag_ptr;
 	struct cds_ja_inode_flag *node_flag,
 		*parent_node_flag,
-		*parent2_node_flag;
+		*parent2_node_flag,
+		*attach_node_flag;
 	int ret;
 
 	if (caa_unlikely(key > ja->key_max)) {
@@ -1148,6 +1175,7 @@ retry:
 	parent_node_flag =
 		(struct cds_ja_inode_flag *) &ja->root;	/* Use root ptr address as key for mutex */
 	attach_node_flag_ptr = &ja->root;
+	attach_node_flag = rcu_dereference(ja->root);
 	node_flag_ptr = &ja->root;
 	node_flag = rcu_dereference(ja->root);
 
@@ -1156,11 +1184,13 @@ retry:
 		uint8_t iter_key;
 
 		dbg_printf("cds_ja_add iter attach_node_flag_ptr %p node_flag_ptr %p node_flag %p\n",
-				*attach_node_flag_ptr, *node_flag_ptr, node_flag);
+				attach_node_flag_ptr, node_flag_ptr, node_flag);
 		if (!ja_node_ptr(node_flag)) {
 			ret = ja_attach_node(ja, attach_node_flag_ptr,
+					attach_node_flag,
 					node_flag_ptr,
-					parent_node_flag, parent2_node_flag,
+					parent_node_flag,
+					parent2_node_flag,
 					key, i, new_node);
 			if (ret == -EAGAIN || ret == -EEXIST)
 				goto retry;
@@ -1172,12 +1202,13 @@ retry:
 		parent_node_flag = node_flag;
 		node_flag = ja_node_get_nth(node_flag,
 			&attach_node_flag_ptr,
+			&attach_node_flag,
 			&node_flag_ptr,
 			iter_key);
 		dbg_printf("cds_ja_add iter key lookup %u finds node_flag %p attach_node_flag_ptr %p node_flag_ptr %p\n",
 				(unsigned int) iter_key, node_flag,
-				*attach_node_flag_ptr,
-				*node_flag_ptr);
+				attach_node_flag_ptr,
+				node_flag_ptr);
 	}
 
 	/*
@@ -1185,15 +1216,17 @@ retry:
 	 * level, or chain it if key is already present.
 	 */
 	if (!ja_node_ptr(node_flag)) {
-		dbg_printf("cds_ja_add last attach_node_flag_ptr %p node_flag_ptr %p node_flag %p\n",
-				*attach_node_flag_ptr, *node_flag_ptr, node_flag);
+		dbg_printf("cds_ja_add attach_node_flag_ptr %p node_flag_ptr %p node_flag %p\n",
+				attach_node_flag_ptr, node_flag_ptr, node_flag);
 		ret = ja_attach_node(ja, attach_node_flag_ptr,
+				attach_node_flag,
 				node_flag_ptr, parent_node_flag,
 				parent2_node_flag, key, i, new_node);
 	} else {
 		ret = ja_chain_node(ja,
 			parent_node_flag,
 			node_flag_ptr,
+			node_flag,
 			(struct cds_hlist_head *) attach_node_flag_ptr,
 			new_node);
 	}
@@ -1249,8 +1282,20 @@ int ja_detach_node(struct cds_ja *ja,
 			ret = -EAGAIN;
 			goto end;
 		}
-		assert(shadow_node->nr_child > 0);
 		shadow_nodes[nr_shadow++] = shadow_node;
+
+		/*
+		 * Check if node has been removed between RCU
+		 * lookup and lock acquisition.
+		 */
+		assert(snapshot_ptr[i + 1]);
+		if (ja_node_ptr(*snapshot_ptr[i + 1])
+				!= ja_node_ptr(snapshot[i + 1])) {
+			ret = -ENOENT;
+			goto end;
+		}
+
+		assert(shadow_node->nr_child > 0);
 		if (shadow_node->nr_child == 1 && i > 1)
 			nr_clear++;
 		nr_branch++;
@@ -1263,10 +1308,23 @@ int ja_detach_node(struct cds_ja *ja,
 				goto end;
 			}
 			shadow_nodes[nr_shadow++] = shadow_node;
+
+			/*
+			 * Check if node has been removed between RCU
+			 * lookup and lock acquisition.
+			 */
+			assert(snapshot_ptr[i]);
+			if (ja_node_ptr(*snapshot_ptr[i])
+					!= ja_node_ptr(snapshot[i])) {
+				ret = -ENOENT;
+				goto end;
+			}
+
 			node_flag_ptr = snapshot_ptr[i + 1];
 			n = snapshot_n[i + 1];
 			parent_node_flag_ptr = snapshot_ptr[i];
 			parent_node_flag = snapshot[i];
+
 			if (i > 1) {
 				/*
 				 * Lock parent's parent, in case we need
@@ -1279,27 +1337,29 @@ int ja_detach_node(struct cds_ja *ja,
 					goto end;
 				}
 				shadow_nodes[nr_shadow++] = shadow_node;
+
+				/*
+				 * Check if node has been removed between RCU
+				 * lookup and lock acquisition.
+				 */
+				assert(snapshot_ptr[i - 1]);
+				if (ja_node_ptr(*snapshot_ptr[i - 1])
+						!= ja_node_ptr(snapshot[i - 1])) {
+					ret = -ENOENT;
+					goto end;
+				}
 			}
+
 			break;
 		}
 	}
 
-	/*
-	 * Check if node has been removed between RCU lookup and lock
-	 * acquisition.
-	 */
-	assert(node_flag_ptr);
-	if (!ja_node_ptr(*node_flag_ptr)) {
-		ret = -ENOENT;
-		goto end;
-	}
-
 	/*
 	 * At this point, we want to delete all nodes that are about to
 	 * be removed from shadow_nodes (except the last one, which is
 	 * either the root or the parent of the upmost node with 1
-	 * child). OK to as to free lock here, because RCU read lock is
-	 * held, and free only performed in call_rcu.
+	 * child). OK to free lock here, because RCU read lock is held,
+	 * and free only performed in call_rcu.
 	 */
 
 	for (i = 0; i < nr_clear; i++) {
@@ -1336,33 +1396,47 @@ static
 int ja_unchain_node(struct cds_ja *ja,
 		struct cds_ja_inode_flag *parent_node_flag,
 		struct cds_ja_inode_flag **node_flag_ptr,
-		struct cds_hlist_head *head,
+		struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_node *node)
 {
 	struct cds_ja_shadow_node *shadow_node;
 	struct cds_hlist_node *hlist_node;
-	int ret = 0, count = 0;
+	struct cds_hlist_head hlist_head;
+	int ret = 0, count = 0, found = 0;
 
 	shadow_node = rcuja_shadow_lookup_lock(ja->ht, parent_node_flag);
 	if (!shadow_node)
 		return -EAGAIN;
-	if (!ja_node_ptr(*node_flag_ptr)) {
+	if (ja_node_ptr(*node_flag_ptr) != ja_node_ptr(node_flag)) {
 		ret = -EAGAIN;
 		goto end;
 	}
+	hlist_head.next = (struct cds_hlist_node *) ja_node_ptr(node_flag);
 	/*
 	 * Retry if another thread removed all but one of duplicates
 	 * since check (this check was performed without lock).
+	 * Ensure that the node we are about to remove is still in the
+	 * list (while holding lock).
 	 */
-	cds_hlist_for_each_rcu(hlist_node, head, list) {
+	cds_hlist_for_each_rcu(hlist_node, &hlist_head) {
+		if (count == 0) {
+			/* FIXME: currently a work-around */
+			hlist_node->prev = (struct cds_hlist_node *) node_flag_ptr;
+		}
 		count++;
+		if (hlist_node == &node->list)
+			found++;
 	}
-
-	if (count == 1) {
+	assert(found <= 1);
+	if (!found || count == 1) {
 		ret = -EAGAIN;
 		goto end;
 	}
 	cds_hlist_del_rcu(&node->list);
+	/*
+	 * Validate that we indeed removed the node from linked list.
+	 */
+	assert(ja_node_ptr(*node_flag_ptr) != (struct cds_ja_inode *) node);
 end:
 	rcuja_shadow_unlock(shadow_node);
 	return ret;
@@ -1417,13 +1491,13 @@ retry:
 		snapshot[nr_snapshot++] = node_flag;
 		node_flag = ja_node_get_nth(node_flag,
 			&prev_node_flag_ptr,
+			NULL,
 			&node_flag_ptr,
 			iter_key);
 		dbg_printf("cds_ja_del iter key lookup %u finds node_flag %p, prev_node_flag_ptr %p\n",
 				(unsigned int) iter_key, node_flag,
 				prev_node_flag_ptr);
 	}
-
 	/*
 	 * We reached bottom of tree, try to find the node we are trying
 	 * to remove. Fail if we cannot find it.
@@ -1465,7 +1539,7 @@ retry:
 					snapshot_n, nr_snapshot, key, node);
 		} else {
 			ret = ja_unchain_node(ja, snapshot[nr_snapshot - 1],
-				node_flag_ptr, &hlist_head, match);
+				node_flag_ptr, node_flag, match);
 		}
 	}
 	/*