rculfhash: use node instead of iter argument for deletion

[urcu.git] / urcu / rculfhash.h

diff --git a/urcu/rculfhash.h b/urcu/rculfhash.h
index 6ed7c8c75b1db697d78fe4c5c8efaef5601176ae..b33ede09cfa664388b9f094e78d60a6161936bba 100644 (file)
--- a/urcu/rculfhash.h
+++ b/urcu/rculfhash.h
@@ -39,8 +39,15 @@ extern "C" {
  * cds_lfht_node: Contains the next pointers and reverse-hash
  * value required for lookup and traversal of the hash table.
  *
- * struct cds_lfht_node should be aligned on 4-bytes boundaries because
- * the two lower bits are used as flags.
+ * struct cds_lfht_node should be aligned on 8-bytes boundaries because
+ * the three lower bits are used as flags. It is worth noting that the
+ * information contained within these three bits could be represented on
+ * two bits by re-using the same bit for REMOVAL_OWNER_FLAG and
+ * BUCKET_FLAG. This can be done if we ensure that no iterator nor
+ * updater check the BUCKET_FLAG after it detects that the REMOVED_FLAG
+ * is set. Given the minimum size of struct cds_lfht_node is 8 bytes on
+ * 32-bit architectures, we choose to go for simplicity and reserve
+ * three bits.
  *
  * 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
@@ -51,9 +58,9 @@ extern "C" {
  * of the hash value for cds_lfht APIs.
  */
 struct cds_lfht_node {
-       struct cds_lfht_node *next;     /* ptr | BUCKET_FLAG | REMOVED_FLAG */
+       struct cds_lfht_node *next;     /* ptr | REMOVAL_OWNER_FLAG | BUCKET_FLAG | REMOVED_FLAG */
        unsigned long reverse_hash;
-} __attribute__((aligned(4)));
+} __attribute__((aligned(8)));
 
 /* cds_lfht_iter: Used to track state while traversing a hash chain. */
 struct cds_lfht_iter {
@@ -154,7 +161,7 @@ struct cds_lfht *cds_lfht_new(unsigned long init_size,
                        pthread_attr_t *attr)
 {
        return _cds_lfht_new(init_size, min_nr_alloc_buckets, max_nr_buckets,
-                       flags, &cds_lfht_mm_order, &rcu_flavor, attr);
+                       flags, NULL, &rcu_flavor, attr);
 }
 
 /*
@@ -175,7 +182,6 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
  * @ht: the hash table.
  * @split_count_before: Sample the node count split-counter before traversal.
  * @count: Traverse the hash table, count the number of nodes observed.
- * @removed: Number of logically removed nodes observed during traversal.
  * @split_count_after: Sample the node count split-counter after traversal.
  *
  * Call with rcu_read_lock held.
@@ -184,7 +190,6 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr);
 void cds_lfht_count_nodes(struct cds_lfht *ht,
                long *split_count_before,
                unsigned long *count,
-               unsigned long *removed,
                long *split_count_after);
 
 /*
@@ -349,14 +354,14 @@ int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
 /*
  * cds_lfht_del - remove node pointed to by iterator from hash table.
  * @ht: the hash table.
- * @iter: the iterator position of the node to delete.
+ * @node: the node to delete.
  *
  * Return 0 if the node is successfully removed, negative value
  * otherwise.
- * Replacing a NULL node or an already removed node will fail with a
+ * Deleting 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.
+ * Node can be looked up with cds_lfht_lookup and cds_lfht_next,
+ * followed by use of cds_lfht_iter_get_node.
  * RCU read-side lock must be held between lookup and removal.
  * Call with rcu_read_lock held.
  * Threads calling this API need to be registered RCU read-side threads.
@@ -364,7 +369,7 @@ int cds_lfht_replace(struct cds_lfht *ht, struct cds_lfht_iter *old_iter,
  * 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_iter *iter);
+int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node);
 
 /*
  * cds_lfht_resize - Force a hash table resize