rcuja: extend API documentation

[userspace-rcu.git] / urcu / rcuja.h

diff --git a/urcu/rcuja.h b/urcu/rcuja.h
index e66ce7e9288095458377ca35eba046ce18959780..2a0de286256b46bb12dabe07d95c85151ed16ccf 100644 (file)
--- a/urcu/rcuja.h
+++ b/urcu/rcuja.h
@@ -36,11 +36,12 @@
 extern "C" {
 #endif
 
+/*
+ * Duplicate nodes with the same key are chained into a singly-linked
+ * list. The last item of this list has a NULL next pointer.
+ */
 struct cds_ja_node {
-       /* Linked list of nodes with same key */
-       struct cds_hlist_node list;
-       /* delayed reclaim */
-       struct rcu_head head;
+       struct cds_ja_node *next;
 };
 
 struct cds_ja;
@@ -57,30 +58,105 @@ void cds_ja_node_init(struct cds_ja_node *node)
 {
 }
 
-struct cds_hlist_head cds_ja_lookup(struct cds_ja *ja, uint64_t key);
-struct cds_hlist_head cds_ja_lookup_lower_equal(struct cds_ja *ja,
+/*
+ * cds_ja_lookup - look up by key.
+ * @ja: the Judy array.
+ * @key: key to look up.
+ *
+ * Returns the first node of a duplicate chain if a match is found, else
+ * returns NULL.
+ * A RCU read-side lock should be held across call to this function and
+ * use of its return value.
+ */
+struct cds_ja_node *cds_ja_lookup(struct cds_ja *ja, uint64_t key);
+
+/*
+ * cds_ja_lookup_lower_equal - look up first node with key <= @key.
+ * @ja: the Judy array.
+ * @key: key to look up.
+ *
+ * Returns the first node of a duplicate chain if a node is present in
+ * the tree which has a key lower or equal to @key, else returns NULL.
+ * A RCU read-side lock should be held across call to this function and
+ * use of its return value.
+ */
+struct cds_ja_node *cds_ja_lookup_lower_equal(struct cds_ja *ja,
                uint64_t key);
 
+/*
+ * cds_ja_add - Add @node at @key, allowing duplicates.
+ * @ja: the Judy array.
+ * @key: key at which @node should be added.
+ * @node: node to add.
+ *
+ * Returns 0 on success, negative error value on error.
+ * A RCU read-side lock should be held across call to this function.
+ */
 int cds_ja_add(struct cds_ja *ja, uint64_t key,
-               struct cds_ja_node *new_node);
+               struct cds_ja_node *node);
 
+/*
+ * cds_ja_add_unique - Add @node at @key, without duplicates.
+ * @ja: the Judy array.
+ * @key: key at which @node should be added.
+ * @node: node to add.
+ *
+ * Returns @node if successfully added, else returns the already
+ * existing node (acts as a RCU lookup).
+ * A RCU read-side lock should be held across call to this function and
+ * use of its return value.
+ */
 struct cds_ja_node *cds_ja_add_unique(struct cds_ja *ja, uint64_t key,
-               struct cds_ja_node *new_node);
+               struct cds_ja_node *node);
 
+/*
+ * cds_ja_del - Remove @node at @key.
+ * @ja: the Judy array.
+ * @key: key at which @node is expected.
+ * @node: node to remove.
+ *
+ * Returns 0 on success, negative error value on error.
+ * A RCU read-side lock should be held across call to this function.
+ */
 int cds_ja_del(struct cds_ja *ja, uint64_t key,
                struct cds_ja_node *node);
 
 struct cds_ja *_cds_ja_new(unsigned int key_bits,
                const struct rcu_flavor_struct *flavor);
 
+/*
+ * cds_ja_new - Create a Judy array.
+ * @key_bits: Number of bits for key.
+ *
+ * Returns non-NULL pointer on success, else NULL on error. @key_bits
+ * needs to be multiple of 8, either: 8, 16, 24, 32, 40, 48, 56, or 64.
+ */
 static inline
 struct cds_ja *cds_ja_new(unsigned int key_bits)
 {
        return _cds_ja_new(key_bits, &rcu_flavor);
 }
 
+/*
+ * cds_ja_destroy - Destroy a Judy array.
+ * @ja: the Judy array.
+ * @rcu_free_node_cb: callback performing memory free of leftover nodes.
+ *
+ * Returns 0 on success, negative error value on error.
+ * The @rcu_free_node_cb callback should internally wait for a grace
+ * period before freeing the node.
+ */
 int cds_ja_destroy(struct cds_ja *ja,
-               void (*free_node_cb)(struct rcu_head *head));
+               void (*rcu_free_node_cb)(struct cds_ja_node *node));
+
+/*
+ * Iterate through duplicates returned by cds_ja_lookup*()
+ * This must be done while rcu_read_lock() is held.
+ * Receives a struct cds_ja_node * as parameter, which is used as start
+ * of duplicate list and loop cursor.
+ */
+#define cds_ja_for_each_duplicate_rcu(pos)                             \
+       for (; (pos) != NULL; (pos) = rcu_dereference((pos)->next))
 
 #ifdef __cplusplus
 }