X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=urcu%2Frculfhash.h;h=0a739ee86f7d11b1e9caa4b8bbb9091dbc0ff1b9;hp=359edb574661400d53c3a2a94c79bf185fa67eb7;hb=6b262fd76774cdd6c7ec62d2a74515d9a28c2317;hpb=48ed1c184a1aa1da7d84c2d0bc1b9528627248ac

diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
index 359edb5..0a739ee 100644
--- a/urcu/rculfhash.h
+++ b/urcu/rculfhash.h
@@ -34,14 +34,19 @@ extern "C" {
 
 /*
  * struct cds_lfht_node and struct _cds_lfht_node should be aligned on
- * 8-bytes boundaries because the two lower bits are used as flags.
+ * 4-bytes boundaries because the two lower bits are used as flags.
  */
 
 struct _cds_lfht_node {
-	struct cds_lfht_node *next;	/* ptr | DUMMY_FLAG | GC_FLAG | REMOVED_FLAG */
+	struct cds_lfht_node *next;	/* ptr | DUMMY_FLAG | REMOVED_FLAG */
 	unsigned long reverse_hash;
-} __attribute__((aligned(8)));
+} __attribute__((aligned(4)));
 
+/*
+ * struct cds_lfht_node can be embedded into a structure (as a field).
+ * caa_container_of() can be used to get the structure from the struct
+ * cds_lfht_node after a lookup.
+ */
 struct cds_lfht_node {
 	/* cache-hot for iteration */
 	struct _cds_lfht_node p;          /* needs to be first field */
@@ -51,6 +56,16 @@ struct cds_lfht_node {
 	struct rcu_head head;
 };
 
+struct cds_lfht_iter {
+	struct cds_lfht_node *node, *next;
+};
+
+static inline
+struct cds_lfht_node *cds_lfht_iter_get_node(struct cds_lfht_iter *iter)
+{
+	return iter->node;
+}
+
 struct cds_lfht;
 
 /*
@@ -155,26 +170,49 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
  * Call with rcu_read_lock held.
  */
 void cds_lfht_count_nodes(struct cds_lfht *ht,
-			unsigned long *count,
-			unsigned long *removed);
+		long *approx_before,
+		unsigned long *count,
+		unsigned long *removed,
+		long *approx_after);
 
 /*
  * cds_lfht_lookup - lookup a node by key.
  *
- * Return NULL if not found.
+ * Output in "*iter". *iter->node set to NULL if not found.
  * Call with rcu_read_lock held.
  */
-struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len);
+void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
+		struct cds_lfht_iter *iter);
 
 /*
- * cds_lfht_next - get the next item with same key (after a lookup).
+ * cds_lfht_next_duplicate - get the next item with same key (after a lookup).
  *
- * Return NULL if no following node exists with same key.
- * RCU read-side lock must be held across cds_lfht_lookup and cds_lfht_next calls, and also
- * between cds_lfht_next calls using the node returned by a previous
- * cds_lfht_next.  Call with rcu_read_lock held.
+ * Uses an iterator initialized by a lookup.
+ * Sets *iter-node to the following node with same key.
+ * Sets *iter->node to NULL if no following node exists with same key.
+ * RCU read-side lock must be held across cds_lfht_lookup and
+ * cds_lfht_next calls, and also between cds_lfht_next calls using the
+ * node returned by a previous cds_lfht_next.
+ * Call with rcu_read_lock held.
+ */
+void cds_lfht_next_duplicate(struct cds_lfht *ht, struct cds_lfht_iter *iter);
+
+/*
+ * cds_lfht_first - get the first node in the table.
+ *
+ * Output in "*iter". *iter->node set to NULL if table is empty.
+ * Call with rcu_read_lock held.
  */
-struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_node *node);
+void cds_lfht_first(struct cds_lfht *ht, struct cds_lfht_iter *iter);
+
+/*
+ * cds_lfht_next - get the next node in the table.
+ *
+ * Input/Output in "*iter". *iter->node set to NULL if *iter was
+ * pointing to the last table node.
+ * Call with rcu_read_lock held.
+ */
+void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 
 /*
  * cds_lfht_add - add a node to the hash table.
@@ -196,12 +234,13 @@ void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node);
  * The semantic of this function is that if only this function is used
  * to add keys into the table, no duplicated keys should ever be
  * observable in the table. The same guarantee apply for combination of
- * add_unique and replace (see below).
+ * add_unique and add_replace (see below).
  */
-struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, struct cds_lfht_node *node);
+struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
+		struct cds_lfht_node *node);
 
 /*
- * cds_lfht_replace - replace a node within hash table.
+ * cds_lfht_add_replace - replace or add a node within hash table.
  *
  * Return the node replaced upon success. If no node matching the key
  * was present, return NULL, which also means the operation succeeded.
@@ -211,33 +250,60 @@ struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht, struct cds_lfht_n
  * freeing the memory reserved for the returned node.
  *
  * The semantic of replacement vs lookups is the following: if lookups
- * are performed between a key insertion and its removal, we guarantee
- * that the lookups will always find the key if it is replaced
- * concurrently with the lookups. Providing this guarantee require us to
- * pin the node to remove in place (disallowing any insertion after this
- * node temporarily) before we can proceed to its exchange with the new
- * node atomically. This renders the "replace" operation not strictly
- * lock-free, because a thread crashing in the middle of the replace
- * operation could stop progress for other updaters.
+ * are performed between a key unique insertion and its removal, we
+ * guarantee that the lookups and get next will always find exactly one
+ * instance of the key if it is replaced concurrently with the lookups.
+ *
+ * Providing this semantic allows us to ensure that replacement-only
+ * schemes will never generate duplicated keys. It also allows us to
+ * guarantee that a combination of add_replace and add_unique updates
+ * will never generate duplicated keys.
+ */
+struct cds_lfht_node *cds_lfht_add_replace(struct cds_lfht *ht,
+		struct cds_lfht_node *node);
+
+/*
+ * cds_lfht_replace - replace a node pointer to by iter within hash table.
+ *
+ * Return 0 if replacement is successful, negative value otherwise.
+ * Replacing a NULL old node or an already removed node will fail with a
+ * negative value.
+ * Old node can be looked up with cds_lfht_lookup and cds_lfht_next.
+ * RCU read-side lock must be held between lookup and replacement.
+ * Call with rcu_read_lock held.
+ * After successful replacement, a grace period must be waited for before
+ * freeing the memory reserved for the old node (which can be accessed
+ * with cds_lfht_iter_get_node).
+ *
+ * The semantic of replacement vs lookups is the following: if lookups
+ * are performed between a key unique insertion and its removal, we
+ * guarantee that the lookups and get next will always find exactly one
+ * instance of the key if it is replaced concurrently with the lookups.
  *
  * Providing this semantic allows us to ensure that replacement-only
  * schemes will never generate duplicated keys. It also allows us to
- * guarantee that a combination of replacement and add_unique updates
+ * guarantee that a combination of add_replace and add_unique updates
  * will never generate duplicated keys.
  */
-struct cds_lfht_node *cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_node *node);
+int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
+		struct cds_lfht_node *new_node);
 
 /*
- * cds_lfht_del - remove node from hash table.
+ * cds_lfht_del - remove node pointed to by iterator from hash table.
  *
- * Return 0 if the node is successfully removed.
- * Node can be looked up with cds_lfht_lookup. RCU read-side lock must
- * be held between lookup and removal.
+ * Return 0 if the node is successfully removed, negative value
+ * otherwise.
+ * Replacing a NULL node or an already removed node will fail with a
+ * negative value.
+ * Node can be looked up with cds_lfht_lookup and cds_lfht_next.
+ * cds_lfht_iter_get_node.
+ * RCU read-side lock must be held between lookup and removal.
  * Call with rcu_read_lock held.
  * After successful removal, a grace period must be waited for before
- * freeing the memory reserved for node.
+ * freeing the memory reserved for old node (which can be accessed with
+ * cds_lfht_iter_get_node).
  */
-int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node);
+int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_iter *iter);
 
 /*
  * cds_lfht_resize - Force a hash table resize