X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=1487980c832c115154937cda4b185024636f9e44;hp=1391b6bb630102c18138ffe953e745e806808d62;hb=b198f0fda77c816d80f63cfa2e71a7e0b4496736;hpb=7fb6f7638628c96521849489b11eaceb473f280b

diff --git a/rculfhash.c b/rculfhash.c
index 1391b6b..1487980 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -167,14 +167,9 @@
 #define CHAIN_LEN_RESIZE_THRESHOLD	3
 
 /*
- * Define the minimum table size. Protects against hash table resize overload
- * when too many entries are added quickly before the resize can complete.
- * This is especially the case if the table could be shrinked to a size of 1.
- * TODO: we might want to make the add/remove operations help the resize to
- * add or remove dummy nodes when a resize is ongoing to ensure upper-bound on
- * chain length.
+ * Define the minimum table size.
  */
-#define MIN_TABLE_SIZE			128
+#define MIN_TABLE_SIZE			1
 
 #if (CAA_BITS_PER_LONG == 32)
 #define MAX_TABLE_ORDER			32
@@ -182,6 +177,12 @@
 #define MAX_TABLE_ORDER			64
 #endif
 
+/*
+ * Minimum number of dummy nodes to touch per thread to parallelize grow/shrink.
+ */
+#define MIN_PARTITION_PER_THREAD_ORDER	12
+#define MIN_PARTITION_PER_THREAD	(1UL << MIN_PARTITION_PER_THREAD_ORDER)
+
 #ifndef min
 #define min(a, b)	((a) < (b) ? (a) : (b))
 #endif
@@ -192,6 +193,8 @@
 
 /*
  * The removed flag needs to be updated atomically with the pointer.
+ * It indicates that no node must attach to the node scheduled for
+ * removal, and that node garbage collection must be performed.
  * The dummy flag does not require to be updated atomically with the
  * pointer, but it is added as a pointer low bit flag to save space.
  */
@@ -199,8 +202,11 @@
 #define DUMMY_FLAG		(1UL << 1)
 #define FLAGS_MASK		((1UL << 2) - 1)
 
+/* Value of the end pointer. Should not interact with flags. */
+#define END_VALUE		NULL
+
 struct ht_items_count {
-	unsigned long add, remove;
+	unsigned long add, del;
 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 
 struct rcu_level {
@@ -237,6 +243,9 @@ struct cds_lfht {
 	void (*cds_lfht_rcu_read_unlock)(void);
 	void (*cds_lfht_rcu_thread_offline)(void);
 	void (*cds_lfht_rcu_thread_online)(void);
+	void (*cds_lfht_rcu_register_thread)(void);
+	void (*cds_lfht_rcu_unregister_thread)(void);
+	pthread_attr_t *resize_attr;	/* Resize threads attributes */
 	unsigned long count;		/* global approximate item count */
 	struct ht_items_count *percpu_count;	/* per-cpu item count */
 };
@@ -246,6 +255,26 @@ struct rcu_resize_work {
 	struct cds_lfht *ht;
 };
 
+struct partition_resize_work {
+	struct rcu_head head;
+	struct cds_lfht *ht;
+	unsigned long i, start, len;
+	void (*fct)(struct cds_lfht *ht, unsigned long i,
+		    unsigned long start, unsigned long len);
+};
+
+enum add_mode {
+	ADD_DEFAULT = 0,
+	ADD_UNIQUE = 1,
+	ADD_REPLACE = 2,
+};
+
+static
+struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
+				unsigned long size,
+				struct cds_lfht_node *node,
+				enum add_mode mode, int dummy);
+
 /*
  * Algorithm to reverse bits in a word by lookup table, extended to
  * 64-bit words.
@@ -544,7 +573,7 @@ void ht_count_add(struct cds_lfht *ht, unsigned long size)
 }
 
 static
-void ht_count_remove(struct cds_lfht *ht, unsigned long size)
+void ht_count_del(struct cds_lfht *ht, unsigned long size)
 {
 	unsigned long percpu_count;
 	int cpu;
@@ -554,18 +583,18 @@ void ht_count_remove(struct cds_lfht *ht, unsigned long size)
 	cpu = ht_get_cpu();
 	if (unlikely(cpu < 0))
 		return;
-	percpu_count = uatomic_add_return(&ht->percpu_count[cpu].remove, -1);
+	percpu_count = uatomic_add_return(&ht->percpu_count[cpu].del, -1);
 	if (unlikely(!(percpu_count & ((1UL << COUNT_COMMIT_ORDER) - 1)))) {
 		unsigned long count;
 
-		dbg_printf("remove percpu %lu\n", percpu_count);
+		dbg_printf("del percpu %lu\n", percpu_count);
 		count = uatomic_add_return(&ht->count,
 					   -(1UL << COUNT_COMMIT_ORDER));
 		/* If power of 2 */
 		if (!(count & (count - 1))) {
 			if ((count >> CHAIN_LEN_RESIZE_THRESHOLD) >= size)
 				return;
-			dbg_printf("remove set global %lu\n", count);
+			dbg_printf("del set global %lu\n", count);
 			cds_lfht_resize_lazy_count(ht, size,
 				count >> (CHAIN_LEN_TARGET - 1));
 		}
@@ -593,7 +622,7 @@ void ht_count_add(struct cds_lfht *ht, unsigned long size)
 }
 
 static
-void ht_count_remove(struct cds_lfht *ht, unsigned long size)
+void ht_count_del(struct cds_lfht *ht, unsigned long size)
 {
 }
 
@@ -651,7 +680,19 @@ struct cds_lfht_node *flag_dummy(struct cds_lfht_node *node)
 {
 	return (struct cds_lfht_node *) (((unsigned long) node) | DUMMY_FLAG);
 }
- 
+
+static
+struct cds_lfht_node *get_end(void)
+{
+	return (struct cds_lfht_node *) END_VALUE;
+}
+
+static
+int is_end(struct cds_lfht_node *node)
+{
+	return clear_flag(node) == (struct cds_lfht_node *) END_VALUE;
+}
+
 static
 unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
 {
@@ -699,7 +740,7 @@ void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node
 		 */
 		assert(dummy != node);
 		for (;;) {
-			if (unlikely(!clear_flag(iter)))
+			if (unlikely(is_end(iter)))
 				return;
 			if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
 				return;
@@ -714,18 +755,21 @@ void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node
 			new_next = flag_dummy(clear_flag(next));
 		else
 			new_next = clear_flag(next);
+		if (is_removed(iter))
+			new_next = flag_removed(new_next);
 		(void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next);
 	}
+	return;
 }
 
 static
 struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
 				unsigned long size,
 				struct cds_lfht_node *node,
-				int unique, int dummy)
+				enum add_mode mode, int dummy)
 {
 	struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
-			*dummy_node;
+			*dummy_node, *return_node;
 	struct _cds_lfht_node *lookup;
 	unsigned long hash, index, order;
 
@@ -733,7 +777,7 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
 	assert(!is_removed(node));
 	if (!size) {
 		assert(dummy);
-		node->p.next = flag_dummy(NULL);
+		node->p.next = flag_dummy(get_end());
 		return node;	/* Initial first add (head) */
 	}
 	hash = bit_reverse_ulong(node->p.reverse_hash);
@@ -752,19 +796,23 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
 		iter = rcu_dereference(iter_prev->p.next);
 		assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
 		for (;;) {
-			if (unlikely(!clear_flag(iter)))
+			if (unlikely(is_end(iter)))
 				goto insert;
 			if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
 				goto insert;
 			next = rcu_dereference(clear_flag(iter)->p.next);
 			if (unlikely(is_removed(next)))
 				goto gc_node;
-			if (unique
+			if ((mode == ADD_UNIQUE || mode == ADD_REPLACE)
 			    && !is_dummy(next)
 			    && !ht->compare_fct(node->key, node->key_len,
 						clear_flag(iter)->key,
-						clear_flag(iter)->key_len))
-				return clear_flag(iter);
+						clear_flag(iter)->key_len)) {
+				if (mode == ADD_UNIQUE)
+					return clear_flag(iter);
+				else /* mode == ADD_REPLACE */
+					goto replace;
+			}
 			/* Only account for identical reverse hash once */
 			if (iter_prev->p.reverse_hash != clear_flag(iter)->p.reverse_hash
 			    && !is_dummy(next))
@@ -772,6 +820,7 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
 			iter_prev = clear_flag(iter);
 			iter = next;
 		}
+
 	insert:
 		assert(node != clear_flag(iter));
 		assert(!is_removed(iter_prev));
@@ -786,10 +835,49 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
 		else
 			new_node = node;
 		if (uatomic_cmpxchg(&iter_prev->p.next, iter,
-				    new_node) != iter)
+				    new_node) != iter) {
 			continue;	/* retry */
+		} else {
+			if (mode == ADD_REPLACE)
+				return_node = NULL;
+			else	/* ADD_DEFAULT and ADD_UNIQUE */
+				return_node = node;
+			goto gc_end;
+		}
+
+	replace:
+		/* Insert after node to be replaced */
+		iter_prev = clear_flag(iter);
+		iter = next;
+		assert(node != clear_flag(iter));
+		assert(!is_removed(iter_prev));
+		assert(!is_removed(iter));
+		assert(iter_prev != node);
+		assert(!dummy);
+		node->p.next = clear_flag(iter);
+		if (is_dummy(iter))
+			new_node = flag_dummy(node);
 		else
+			new_node = node;
+		/*
+		 * Here is the whole trick for lock-free replace: we add
+		 * the replacement node _after_ the node we want to
+		 * replace by atomically setting its next pointer at the
+		 * same time we set its removal flag. Given that
+		 * the lookups/get next use an iterator aware of the
+		 * next pointer, they will either skip the old node due
+		 * to the removal flag and see the new node, or use
+		 * the old node, but will not see the new one.
+		 */
+		new_node = flag_removed(new_node);
+		if (uatomic_cmpxchg(&iter_prev->p.next,
+			      iter, new_node) != iter) {
+			continue;	/* retry */
+		} else {
+			return_node = iter_prev;
 			goto gc_end;
+		}
+
 	gc_node:
 		assert(!is_removed(iter));
 		if (is_dummy(iter))
@@ -806,11 +894,11 @@ gc_end:
 	lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
 	dummy_node = (struct cds_lfht_node *) lookup;
 	_cds_lfht_gc_bucket(dummy_node, node);
-	return node;
+	return return_node;
 }
 
 static
-int _cds_lfht_remove(struct cds_lfht *ht, unsigned long size,
+int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
 		struct cds_lfht_node *node,
 		int dummy_removal)
 {
@@ -824,6 +912,8 @@ int _cds_lfht_remove(struct cds_lfht *ht, unsigned long size,
 	assert(!is_removed(node));
 	old = rcu_dereference(node->p.next);
 	do {
+		struct cds_lfht_node *new_next;
+
 		next = old;
 		if (unlikely(is_removed(next)))
 			goto end;
@@ -831,8 +921,8 @@ int _cds_lfht_remove(struct cds_lfht *ht, unsigned long size,
 			assert(is_dummy(next));
 		else
 			assert(!is_dummy(next));
-		old = uatomic_cmpxchg(&node->p.next, next,
-				      flag_removed(next));
+		new_next = flag_removed(next);
+		old = uatomic_cmpxchg(&node->p.next, next, new_next);
 	} while (old != next);
 
 	/* We performed the (logical) deletion. */
@@ -863,49 +953,103 @@ end:
 }
 
 static
-void init_table_hash(struct cds_lfht *ht, unsigned long i,
-		unsigned long len)
+void *partition_resize_thread(void *arg)
 {
-	unsigned long j;
+	struct partition_resize_work *work = arg;
 
-	for (j = 0; j < len; j++) {
-		struct cds_lfht_node *new_node =
-			(struct cds_lfht_node *) &ht->t.tbl[i]->nodes[j];
+	work->ht->cds_lfht_rcu_register_thread();
+	work->fct(work->ht, work->i, work->start, work->len);
+	work->ht->cds_lfht_rcu_unregister_thread();
+	return NULL;
+}
 
-		dbg_printf("init hash entry: i %lu j %lu hash %lu\n",
-			   i, j, !i ? 0 : (1UL << (i - 1)) + j);
-		new_node->p.reverse_hash =
-			bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
-		if (CMM_LOAD_SHARED(ht->in_progress_destroy))
-			break;
+static
+void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
+		unsigned long len,
+		void (*fct)(struct cds_lfht *ht, unsigned long i,
+			unsigned long start, unsigned long len))
+{
+	unsigned long partition_len;
+	struct partition_resize_work *work;
+	int thread, ret;
+	unsigned long nr_threads;
+	pthread_t *thread_id;
+
+	/*
+	 * Note: nr_cpus_mask + 1 is always power of 2.
+	 * We spawn just the number of threads we need to satisfy the minimum
+	 * partition size, up to the number of CPUs in the system.
+	 */
+	nr_threads = min(nr_cpus_mask + 1,
+			 len >> MIN_PARTITION_PER_THREAD_ORDER);
+	partition_len = len >> get_count_order_ulong(nr_threads);
+	work = calloc(nr_threads, sizeof(*work));
+	thread_id = calloc(nr_threads, sizeof(*thread_id));
+	assert(work);
+	for (thread = 0; thread < nr_threads; thread++) {
+		work[thread].ht = ht;
+		work[thread].i = i;
+		work[thread].len = partition_len;
+		work[thread].start = thread * partition_len;
+		work[thread].fct = fct;
+		ret = pthread_create(&thread_id[thread], ht->resize_attr,
+			partition_resize_thread, &work[thread]);
+		assert(!ret);
+	}
+	for (thread = 0; thread < nr_threads; thread++) {
+		ret = pthread_join(thread_id[thread], NULL);
+		assert(!ret);
 	}
+	free(work);
+	free(thread_id);
 }
 
 /*
  * Holding RCU read lock to protect _cds_lfht_add against memory
  * reclaim that could be performed by other call_rcu worker threads (ABA
  * problem).
+ *
+ * When we reach a certain length, we can split this population phase over
+ * many worker threads, based on the number of CPUs available in the system.
+ * This should therefore take care of not having the expand lagging behind too
+ * many concurrent insertion threads by using the scheduler's ability to
+ * schedule dummy node population fairly with insertions.
  */
 static
-void init_table_link(struct cds_lfht *ht, unsigned long i, unsigned long len)
+void init_table_populate_partition(struct cds_lfht *ht, unsigned long i,
+				   unsigned long start, unsigned long len)
 {
 	unsigned long j;
 
-	ht->cds_lfht_rcu_thread_online();
 	ht->cds_lfht_rcu_read_lock();
-	for (j = 0; j < len; j++) {
+	for (j = start; j < start + len; j++) {
 		struct cds_lfht_node *new_node =
 			(struct cds_lfht_node *) &ht->t.tbl[i]->nodes[j];
 
-		dbg_printf("init link: i %lu j %lu hash %lu\n",
+		dbg_printf("init populate: i %lu j %lu hash %lu\n",
 			   i, j, !i ? 0 : (1UL << (i - 1)) + j);
+		new_node->p.reverse_hash =
+			bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
 		(void) _cds_lfht_add(ht, !i ? 0 : (1UL << (i - 1)),
-				new_node, 0, 1);
+				new_node, ADD_DEFAULT, 1);
 		if (CMM_LOAD_SHARED(ht->in_progress_destroy))
 			break;
 	}
 	ht->cds_lfht_rcu_read_unlock();
-	ht->cds_lfht_rcu_thread_offline();
+}
+
+static
+void init_table_populate(struct cds_lfht *ht, unsigned long i,
+			 unsigned long len)
+{
+	assert(nr_cpus_mask != -1);
+	if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) {
+		ht->cds_lfht_rcu_thread_online();
+		init_table_populate_partition(ht, i, 0, len);
+		ht->cds_lfht_rcu_thread_offline();
+		return;
+	}
+	partition_resize_helper(ht, i, len, init_table_populate_partition);
 }
 
 static
@@ -929,22 +1073,20 @@ void init_table(struct cds_lfht *ht,
 
 		ht->t.tbl[i] = calloc(1, sizeof(struct rcu_level)
 				+ (len * sizeof(struct _cds_lfht_node)));
-
-		/* Set all dummy nodes reverse hash values for a level */
-		init_table_hash(ht, i, len);
+		assert(ht->t.tbl[i]);
 
 		/*
-		 * Link all dummy nodes into the table. Concurrent
-		 * add/remove are helping us.
+		 * Set all dummy nodes reverse hash values for a level and
+		 * link all dummy nodes into the table.
 		 */
-		init_table_link(ht, i, len);
+		init_table_populate(ht, i, len);
 
 		/*
-		 * Update table size (after init for now, because no
-		 * concurrent updater help (TODO)).
+		 * Update table size.
 		 */
 		cmm_smp_wmb();	/* populate data before RCU size */
 		CMM_STORE_SHARED(ht->t.size, !i ? 1 : (1UL << i));
+
 		dbg_printf("init new size: %lu\n", !i ? 1 : (1UL << i));
 		if (CMM_LOAD_SHARED(ht->in_progress_destroy))
 			break;
@@ -970,15 +1112,20 @@ void init_table(struct cds_lfht *ht,
  *
  * Logical removal and garbage collection can therefore be done in batch or on a
  * node-per-node basis, as long as the guarantee above holds.
+ *
+ * When we reach a certain length, we can split this removal over many worker
+ * threads, based on the number of CPUs available in the system. This should
+ * take care of not letting resize process lag behind too many concurrent
+ * updater threads actively inserting into the hash table.
  */
 static
-void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
+void remove_table_partition(struct cds_lfht *ht, unsigned long i,
+			    unsigned long start, unsigned long len)
 {
 	unsigned long j;
 
-	ht->cds_lfht_rcu_thread_online();
 	ht->cds_lfht_rcu_read_lock();
-	for (j = 0; j < len; j++) {
+	for (j = start; j < start + len; j++) {
 		struct cds_lfht_node *fini_node =
 			(struct cds_lfht_node *) &ht->t.tbl[i]->nodes[j];
 
@@ -986,13 +1133,26 @@ void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
 			   i, j, !i ? 0 : (1UL << (i - 1)) + j);
 		fini_node->p.reverse_hash =
 			bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
-		(void) _cds_lfht_remove(ht, !i ? 0 : (1UL << (i - 1)),
+		(void) _cds_lfht_del(ht, !i ? 0 : (1UL << (i - 1)),
 				fini_node, 1);
 		if (CMM_LOAD_SHARED(ht->in_progress_destroy))
 			break;
 	}
 	ht->cds_lfht_rcu_read_unlock();
-	ht->cds_lfht_rcu_thread_offline();
+}
+
+static
+void remove_table(struct cds_lfht *ht, unsigned long i, unsigned long len)
+{
+
+	assert(nr_cpus_mask != -1);
+	if (nr_cpus_mask < 0 || len < 2 * MIN_PARTITION_PER_THREAD) {
+		ht->cds_lfht_rcu_thread_online();
+		remove_table_partition(ht, i, 0, len);
+		ht->cds_lfht_rcu_thread_offline();
+		return;
+	}
+	partition_resize_helper(ht, i, len, remove_table_partition);
 }
 
 static
@@ -1042,7 +1202,7 @@ void fini_table(struct cds_lfht *ht,
 	}
 }
 
-struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
+struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
 			cds_lfht_compare_fct compare_fct,
 			unsigned long hash_seed,
 			unsigned long init_size,
@@ -1053,7 +1213,10 @@ struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
 			void (*cds_lfht_rcu_read_lock)(void),
 			void (*cds_lfht_rcu_read_unlock)(void),
 			void (*cds_lfht_rcu_thread_offline)(void),
-			void (*cds_lfht_rcu_thread_online)(void))
+			void (*cds_lfht_rcu_thread_online)(void),
+			void (*cds_lfht_rcu_register_thread)(void),
+			void (*cds_lfht_rcu_unregister_thread)(void),
+			pthread_attr_t *attr)
 {
 	struct cds_lfht *ht;
 	unsigned long order;
@@ -1062,6 +1225,7 @@ struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
 	if (init_size && (init_size & (init_size - 1)))
 		return NULL;
 	ht = calloc(1, sizeof(struct cds_lfht));
+	assert(ht);
 	ht->hash_fct = hash_fct;
 	ht->compare_fct = compare_fct;
 	ht->hash_seed = hash_seed;
@@ -1071,6 +1235,9 @@ struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
 	ht->cds_lfht_rcu_read_unlock = cds_lfht_rcu_read_unlock;
 	ht->cds_lfht_rcu_thread_offline = cds_lfht_rcu_thread_offline;
 	ht->cds_lfht_rcu_thread_online = cds_lfht_rcu_thread_online;
+	ht->cds_lfht_rcu_register_thread = cds_lfht_rcu_register_thread;
+	ht->cds_lfht_rcu_unregister_thread = cds_lfht_rcu_unregister_thread;
+	ht->resize_attr = attr;
 	ht->percpu_count = alloc_per_cpu_items_count();
 	/* this mutex should not nest in read-side C.S. */
 	pthread_mutex_init(&ht->resize_mutex, NULL);
@@ -1085,9 +1252,10 @@ struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
 	return ht;
 }
 
-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)
 {
-	struct cds_lfht_node *node, *next;
+	struct cds_lfht_node *node, *next, *dummy_node;
 	struct _cds_lfht_node *lookup;
 	unsigned long hash, reverse_hash, index, order, size;
 
@@ -1100,10 +1268,15 @@ struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key
 	lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1))) - 1)];
 	dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
 		   hash, index, order, index & (!order ? 0 : ((1UL << (order - 1)) - 1)));
-	node = (struct cds_lfht_node *) lookup;
+	dummy_node = (struct cds_lfht_node *) lookup;
+	/* We can always skip the dummy node initially */
+	node = rcu_dereference(dummy_node->p.next);
+	node = clear_flag(node);
 	for (;;) {
-		if (unlikely(!node))
+		if (unlikely(is_end(node))) {
+			node = NULL;
 			break;
+		}
 		if (unlikely(node->p.reverse_hash > reverse_hash)) {
 			node = NULL;
 			break;
@@ -1117,26 +1290,29 @@ struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key
 		node = clear_flag(next);
 	}
 	assert(!node || !is_dummy(rcu_dereference(node->p.next)));
-	return node;
+	iter->node = node;
+	iter->next = next;
 }
 
-struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht,
-				struct cds_lfht_node *node)
+void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
 {
-	struct cds_lfht_node *next;
+	struct cds_lfht_node *node, *next;
 	unsigned long reverse_hash;
 	void *key;
 	size_t key_len;
 
+	node = iter->node;
 	reverse_hash = node->p.reverse_hash;
 	key = node->key;
 	key_len = node->key_len;
-	next = rcu_dereference(node->p.next);
+	next = iter->next;
 	node = clear_flag(next);
 
 	for (;;) {
-		if (unlikely(!node))
+		if (unlikely(is_end(node))) {
+			node = NULL;
 			break;
+		}
 		if (unlikely(node->p.reverse_hash > reverse_hash)) {
 			node = NULL;
 			break;
@@ -1150,7 +1326,8 @@ struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht,
 		node = clear_flag(next);
 	}
 	assert(!node || !is_dummy(rcu_dereference(node->p.next)));
-	return node;
+	iter->node = node;
+	iter->next = next;
 }
 
 void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node)
@@ -1161,12 +1338,28 @@ void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node)
 	node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
 
 	size = rcu_dereference(ht->t.size);
-	(void) _cds_lfht_add(ht, size, node, 0, 0);
+	(void) _cds_lfht_add(ht, size, node, ADD_DEFAULT, 0);
 	ht_count_add(ht, size);
 }
 
 struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
-					struct cds_lfht_node *node)
+				struct cds_lfht_node *node)
+{
+	unsigned long hash, size;
+	struct cds_lfht_node *ret;
+
+	hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
+	node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
+
+	size = rcu_dereference(ht->t.size);
+	ret = _cds_lfht_add(ht, size, node, ADD_UNIQUE, 0);
+	if (ret == node)
+		ht_count_add(ht, size);
+	return ret;
+}
+
+struct cds_lfht_node *cds_lfht_replace(struct cds_lfht *ht,
+				struct cds_lfht_node *node)
 {
 	unsigned long hash, size;
 	struct cds_lfht_node *ret;
@@ -1175,21 +1368,21 @@ struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
 	node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
 
 	size = rcu_dereference(ht->t.size);
-	ret = _cds_lfht_add(ht, size, node, 1, 0);
-	if (ret != node)
+	ret = _cds_lfht_add(ht, size, node, ADD_REPLACE, 0);
+	if (ret == NULL)
 		ht_count_add(ht, size);
 	return ret;
 }
 
-int cds_lfht_remove(struct cds_lfht *ht, struct cds_lfht_node *node)
+int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
 {
 	unsigned long size;
 	int ret;
 
 	size = rcu_dereference(ht->t.size);
-	ret = _cds_lfht_remove(ht, size, node, 0);
+	ret = _cds_lfht_del(ht, size, node, 0);
 	if (!ret)
-		ht_count_remove(ht, size);
+		ht_count_del(ht, size);
 	return ret;
 }
 
@@ -1208,7 +1401,7 @@ int cds_lfht_delete_dummy(struct cds_lfht *ht)
 		if (!is_dummy(node))
 			return -EPERM;
 		assert(!is_removed(node));
-	} while (clear_flag(node));
+	} while (!is_end(node));
 	/*
 	 * size accessed without rcu_dereference because hash table is
 	 * being destroyed.
@@ -1234,7 +1427,7 @@ int cds_lfht_delete_dummy(struct cds_lfht *ht)
  * Should only be called when no more concurrent readers nor writers can
  * possibly access the table.
  */
-int cds_lfht_destroy(struct cds_lfht *ht)
+int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
 {
 	int ret;
 
@@ -1246,6 +1439,8 @@ int cds_lfht_destroy(struct cds_lfht *ht)
 	if (ret)
 		return ret;
 	free_per_cpu_items_count(ht->percpu_count);
+	if (attr)
+		*attr = ht->resize_attr;
 	poison_free(ht);
 	return ret;
 }
@@ -1274,7 +1469,7 @@ void cds_lfht_count_nodes(struct cds_lfht *ht,
 		else
 			(nr_dummy)++;
 		node = clear_flag(next);
-	} while (node);
+	} while (!is_end(node));
 	dbg_printf("number of dummy nodes: %lu\n", nr_dummy);
 }