X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=rculfhash.c;h=24783bbdb619d4f4bf39d671780ff756e190f8c8;hb=7ec59d3b56b9a40d2d3027ad90800c9471ae3337;hp=534a2f8764ba8473ed896aa48a6fbc47690da4cf;hpb=65e8e72998f82cca2e86fd108f625905f988b515;p=urcu.git

diff --git a/rculfhash.c b/rculfhash.c
index 534a2f8..24783bb 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -205,12 +205,13 @@ unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
 }
 
 static
-void _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
+int _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node,
+	     int unique)
 {
 	struct rcu_ht_node *iter_prev, *iter, *iter_prev_next, *next;
 
 	if (!t->size)
-		return;
+		return 0;
 	for (;;) {
 		uint32_t chain_len = 0;
 
@@ -232,6 +233,12 @@ void _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
 			next = rcu_dereference(clear_flag(iter)->next);
 			if (unlikely(is_removed(next)))
 				continue;
+			if (unique
+			    && !clear_flag(iter)->dummy
+			    && !ht->compare_fct(node->key, node->key_len,
+					clear_flag(iter)->key,
+					clear_flag(iter)->key_len))
+				return -EEXIST;
 			if (clear_flag(iter)->reverse_hash > node->reverse_hash)
 				break;
 			/* Only account for identical reverse hash once */
@@ -240,7 +247,7 @@ void _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
 			iter_prev = clear_flag(iter);
 			iter_prev_next = next;
 		}
-		assert(node != iter);
+		assert(node != clear_flag(iter));
 		assert(!is_removed(iter_prev));
 		assert(iter_prev != node);
 		node->next = iter;
@@ -250,23 +257,39 @@ void _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
 		else
 			break;
 	}
+	return 0;
 }
 
 static
 int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
 {
 	struct rcu_ht_node *iter_prev, *iter, *iter_prev_next, *next, *old;
-	unsigned long chain_len;
 	int found;
 	int flagged = 0;
 
+	/* logically delete the node */
+	old = rcu_dereference(node->next);
+	do {
+		next = old;
+		if (is_removed(next))
+			goto end;
+		old = uatomic_cmpxchg(&node->next, next,
+				      flag_removed(next));
+	} while (old != next);
+
+	/* We performed the (logical) deletion. */
+	flagged = 1;
+
+	/*
+	 * Ensure that the node is not visible to readers anymore: lookup for
+	 * the node, and remove it if found.
+	 */
 retry:
-	chain_len = 0;
 	found = 0;
 	/*
 	 * iter_prev points to the non-removed node prior to the remove
 	 * location.
-	 * node is the node to remove.
+	 * next points to the non-removed node following the remove location.
 	 */
 	iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
 	/* We can always skip the dummy node initially */
@@ -278,8 +301,9 @@ retry:
 		if (unlikely(!clear_flag(iter)))
 			break;
 		next = rcu_dereference(clear_flag(iter)->next);
-		if (iter == node) {
+		if (clear_flag(iter) == node) {
 			found = 1;
+			assert(is_removed(rcu_dereference(node->next)));
 			break;
 		}
 		if (unlikely(is_removed(next)))
@@ -291,31 +315,6 @@ retry:
 	} 
 	if (!found)
 		goto end;
-	if (!flagged) {
-		if (is_removed(next))
-			goto end;
-		/* set deletion flag */
-		if ((old = uatomic_cmpxchg(&iter->next, next,
-					   flag_removed(next))) != next) {
-			if (old == flag_removed(next))
-				goto end;
-			else
-				goto retry;
-		}
-		flagged = 1;
-	}
-	/*
-	 * Remove the element from the list.
-	 * - Retry if there has been a concurrent add before us.
-	 * - Retry if the prev node has been deleted (its next removed
-	 *   flag would be set).
-	 * - There cannot be a concurrent delete for our position, because
-	 *   we won the deletion flag cmpxchg.
-	 * - If there is a concurrent add or remove after us while our
-	 *   removed flag is set, it will skip us and link directly after
-	 *   the prior non-removed node before us. In this case, the
-	 *   retry will not find the node in the list anymore.
-	 */
 	if (uatomic_cmpxchg(&iter_prev->next, iter_prev_next,
 			    clear_flag(next)) != iter_prev_next)
 		goto retry;
@@ -324,9 +323,10 @@ end:
 	 * Only the flagging action indicated that we (and no other)
 	 * removed the node from the hash.
 	 */
-	if (flagged)
+	if (flagged) {
+		assert(is_removed(rcu_dereference(node->next)));
 		return 0;
-	else
+	} else
 		return -ENOENT;
 }
 
@@ -345,7 +345,7 @@ void init_table(struct rcu_ht *ht, struct rcu_table *t,
 		t->tbl[i]->dummy = 1;
 		t->tbl[i]->hash = i;
 		t->tbl[i]->reverse_hash = bit_reverse_ulong(i);
-		_ht_add(ht, t, t->tbl[i]);
+		(void) _ht_add(ht, t, t->tbl[i], 0);
 	}
 	t->resize_target = t->size = end;
 	t->resize_initiated = 0;
@@ -412,7 +412,18 @@ void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node)
 	node->reverse_hash = bit_reverse_ulong((unsigned long) node->hash);
 
 	t = rcu_dereference(ht->t);
-	_ht_add(ht, t, node);
+	(void) _ht_add(ht, t, node, 0);
+}
+
+int ht_add_unique(struct rcu_ht *ht, struct rcu_ht_node *node)
+{
+	struct rcu_table *t;
+
+	node->hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
+	node->reverse_hash = bit_reverse_ulong((unsigned long) node->hash);
+
+	t = rcu_dereference(ht->t);
+	return _ht_add(ht, t, node, 1);
 }
 
 int ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node)