X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=rcuja%2Frcuja.c;h=9398a222bcd526fc4d3dcd1f86e851a02a17ced4;hb=refs%2Fheads%2Furcu%2Frcuja-range;hp=e6e3a3e6bcc5a10dcc6f0f24354ac5d2788c0573;hpb=fa1127990db461f839b1ffe2f3dea0ee2c45e89f;p=userspace-rcu.git

diff --git a/rcuja/rcuja.c b/rcuja/rcuja.c
index e6e3a3e..9398a22 100644
--- a/rcuja/rcuja.c
+++ b/rcuja/rcuja.c
@@ -3,7 +3,8 @@
  *
  * Userspace RCU library - RCU Judy Array
  *
- * Copyright 2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2000 - 2002 Hewlett-Packard Company
+ * Copyright 2012-2013 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -24,16 +25,19 @@
 #include <stdint.h>
 #include <errno.h>
 #include <limits.h>
+#include <string.h>
+#include <assert.h>
 #include <urcu/rcuja.h>
 #include <urcu/compiler.h>
 #include <urcu/arch.h>
-#include <assert.h>
 #include <urcu-pointer.h>
 #include <urcu/uatomic.h>
-#include <stdint.h>
 
 #include "rcuja-internal.h"
-#include "bitfield.h"
+
+#ifndef abs
+#define abs_int(a)	((int) (a) > 0 ? (int) (a) : -((int) (a)))
+#endif
 
 enum cds_ja_type_class {
 	RCU_JA_LINEAR = 0,	/* Type A */
@@ -116,14 +120,16 @@ const struct cds_ja_type ja_types[] = {
 	{ .type_class = RCU_JA_LINEAR, .min_child = 10, .max_child = ja_type_4_max_child, .max_linear_child = ja_type_4_max_linear_child, .order = 7, },
 
 	/* Pools may fill sooner than max_child */
+	/* This pool is hardcoded at index 5. See ja_node_ptr(). */
 	{ .type_class = RCU_JA_POOL, .min_child = 20, .max_child = ja_type_5_max_child, .max_linear_child = ja_type_5_max_linear_child, .order = 8, .nr_pool_order = ja_type_5_nr_pool_order, .pool_size_order = 7, },
+	/* This pool is hardcoded at index 6. See ja_node_ptr(). */
 	{ .type_class = RCU_JA_POOL, .min_child = 45, .max_child = ja_type_6_max_child, .max_linear_child = ja_type_6_max_linear_child, .order = 9, .nr_pool_order = ja_type_6_nr_pool_order, .pool_size_order = 7, },
 
 	/*
-	 * TODO: Upon node removal below min_child, if child pool is
-	 * filled beyond capacity, we need to roll back to pigeon.
+	 * Upon node removal below min_child, if child pool is filled
+	 * beyond capacity, we roll back to pigeon.
 	 */
-	{ .type_class = RCU_JA_PIGEON, .min_child = 89, .max_child = ja_type_7_max_child, .order = 10, },
+	{ .type_class = RCU_JA_PIGEON, .min_child = 83, .max_child = ja_type_7_max_child, .order = 10, },
 
 	{ .type_class = RCU_JA_NULL, .min_child = 0, .max_child = ja_type_8_max_child, },
 };
@@ -164,14 +170,16 @@ const struct cds_ja_type ja_types[] = {
 	{ .type_class = RCU_JA_LINEAR, .min_child = 10, .max_child = ja_type_4_max_child, .max_linear_child = ja_type_4_max_linear_child, .order = 8, },
 
 	/* Pools may fill sooner than max_child. */
+	/* This pool is hardcoded at index 5. See ja_node_ptr(). */
 	{ .type_class = RCU_JA_POOL, .min_child = 22, .max_child = ja_type_5_max_child, .max_linear_child = ja_type_5_max_linear_child, .order = 9, .nr_pool_order = ja_type_5_nr_pool_order, .pool_size_order = 8, },
+	/* This pool is hardcoded at index 6. See ja_node_ptr(). */
 	{ .type_class = RCU_JA_POOL, .min_child = 51, .max_child = ja_type_6_max_child, .max_linear_child = ja_type_6_max_linear_child, .order = 10, .nr_pool_order = ja_type_6_nr_pool_order, .pool_size_order = 8, },
 
 	/*
-	 * TODO: Upon node removal below min_child, if child pool is
-	 * filled beyond capacity, we need to roll back to pigeon.
+	 * Upon node removal below min_child, if child pool is filled
+	 * beyond capacity, we roll back to pigeon.
 	 */
-	{ .type_class = RCU_JA_PIGEON, .min_child = 101, .max_child = ja_type_7_max_child, .order = 11, },
+	{ .type_class = RCU_JA_PIGEON, .min_child = 95, .max_child = ja_type_7_max_child, .order = 11, },
 
 	{ .type_class = RCU_JA_NULL, .min_child = 0, .max_child = ja_type_8_max_child, },
 };
@@ -234,19 +242,64 @@ struct cds_ja_inode {
 };
 
 enum ja_recompact {
-	JA_RECOMPACT,
-	JA_RECOMPACT_ADD,
+	JA_RECOMPACT_ADD_SAME,
+	JA_RECOMPACT_ADD_NEXT,
 	JA_RECOMPACT_DEL,
 };
 
-struct cds_ja_inode *alloc_cds_ja_node(const struct cds_ja_type *ja_type)
+enum ja_lookup_inequality {
+	JA_LOOKUP_BE,
+	JA_LOOKUP_AE,
+};
+
+enum ja_direction {
+	JA_LEFT,
+	JA_RIGHT,
+	JA_LEFTMOST,
+	JA_RIGHTMOST,
+};
+
+static
+struct cds_ja_inode *_ja_node_mask_ptr(struct cds_ja_inode_flag *node)
+{
+	return (struct cds_ja_inode *) (((unsigned long) node) & JA_PTR_MASK);
+}
+
+unsigned long ja_node_type(struct cds_ja_inode_flag *node)
+{
+	unsigned long type;
+
+	if (_ja_node_mask_ptr(node) == NULL) {
+		return NODE_INDEX_NULL;
+	}
+	type = (unsigned int) ((unsigned long) node & JA_TYPE_MASK);
+	assert(type < (1UL << JA_TYPE_BITS));
+	return type;
+}
+
+static
+struct cds_ja_inode *alloc_cds_ja_node(struct cds_ja *ja,
+		const struct cds_ja_type *ja_type)
 {
-	return calloc(1U << ja_type->order, sizeof(char));
+	size_t len = 1U << ja_type->order;
+	void *p;
+	int ret;
+
+	ret = posix_memalign(&p, len, len);
+	if (ret || !p) {
+		return NULL;
+	}
+	memset(p, 0, len);
+	if (ja_debug_counters())
+		uatomic_inc(&ja->nr_nodes_allocated);
+	return p;
 }
 
-void free_cds_ja_node(struct cds_ja_inode *node)
+void free_cds_ja_node(struct cds_ja *ja, struct cds_ja_inode *node)
 {
 	free(node);
+	if (ja_debug_counters() && node)
+		uatomic_inc(&ja->nr_nodes_freed);
 }
 
 #define __JA_ALIGN_MASK(v, mask)	(((v) + (mask)) & ~(mask))
@@ -276,7 +329,6 @@ uint8_t ja_linear_node_get_nr_child(const struct cds_ja_type *type,
 static
 struct cds_ja_inode_flag *ja_linear_node_get_nth(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
-		struct cds_ja_inode_flag ***child_node_flag_ptr,
 		struct cds_ja_inode_flag ***node_flag_ptr,
 		uint8_t n)
 {
@@ -305,13 +357,69 @@ struct cds_ja_inode_flag *ja_linear_node_get_nth(const struct cds_ja_type *type,
 	}
 	pointers = (struct cds_ja_inode_flag **) align_ptr_size(&values[type->max_linear_child]);
 	ptr = rcu_dereference(pointers[i]);
-	if (caa_unlikely(child_node_flag_ptr) && ptr)
-		*child_node_flag_ptr = &pointers[i];
 	if (caa_unlikely(node_flag_ptr))
 		*node_flag_ptr = &pointers[i];
 	return ptr;
 }
 
+static
+struct cds_ja_inode_flag *ja_linear_node_get_direction(const struct cds_ja_type *type,
+		struct cds_ja_inode *node,
+		int n, uint8_t *result_key,
+		enum ja_direction dir)
+{
+	uint8_t nr_child;
+	uint8_t *values;
+	struct cds_ja_inode_flag **pointers;
+	struct cds_ja_inode_flag *ptr, *match_ptr = NULL;
+	unsigned int i;
+	int match_v;
+
+	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
+	assert(dir == JA_LEFT || dir == JA_RIGHT);
+
+	if (dir == JA_LEFT) {
+		match_v = -1;
+	} else {
+		match_v = JA_ENTRY_PER_NODE;
+	}
+
+	nr_child = ja_linear_node_get_nr_child(type, node);
+	cmm_smp_rmb();	/* read nr_child before values and pointers */
+	assert(nr_child <= type->max_linear_child);
+	assert(type->type_class != RCU_JA_LINEAR || nr_child >= type->min_child);
+
+	values = &node->u.data[1];
+	pointers = (struct cds_ja_inode_flag **) align_ptr_size(&values[type->max_linear_child]);
+	for (i = 0; i < nr_child; i++) {
+		unsigned int v;
+
+		v = CMM_LOAD_SHARED(values[i]);
+		ptr = CMM_LOAD_SHARED(pointers[i]);
+		if (!ptr)
+			continue;
+		if (dir == JA_LEFT) {
+			if ((int) v < n && (int) v > match_v) {
+				match_v = v;
+				match_ptr = ptr;
+			}
+		} else {
+			if ((int) v > n && (int) v < match_v) {
+				match_v = v;
+				match_ptr = ptr;
+			}
+		}
+	}
+
+	if (!match_ptr) {
+		return NULL;
+	}
+	assert(match_v >= 0 && match_v < JA_ENTRY_PER_NODE);
+
+	*result_key = (uint8_t) match_v;
+	return rcu_dereference(match_ptr);
+}
+
 static
 void ja_linear_node_get_ith_pos(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
@@ -334,21 +442,44 @@ void ja_linear_node_get_ith_pos(const struct cds_ja_type *type,
 static
 struct cds_ja_inode_flag *ja_pool_node_get_nth(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
-		struct cds_ja_inode_flag ***child_node_flag_ptr,
+		struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_inode_flag ***node_flag_ptr,
 		uint8_t n)
 {
 	struct cds_ja_inode *linear;
 
 	assert(type->type_class == RCU_JA_POOL);
-	/*
-	 * TODO: currently, we select the pool by highest bits. We
-	 * should support various encodings.
-	 */
-	linear = (struct cds_ja_inode *)
-		&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
-	return ja_linear_node_get_nth(type, linear, child_node_flag_ptr,
-		node_flag_ptr, n);
+
+	switch (type->nr_pool_order) {
+	case 1:
+	{
+		unsigned long bitsel, index;
+
+		bitsel = ja_node_pool_1d_bitsel(node_flag);
+		assert(bitsel < CHAR_BIT);
+		index = ((unsigned long) n >> bitsel) & 0x1;
+		linear = (struct cds_ja_inode *) &node->u.data[index << type->pool_size_order];
+		break;
+	}
+	case 2:
+	{
+		unsigned long bitsel[2], index[2], rindex;
+
+		ja_node_pool_2d_bitsel(node_flag, bitsel);
+		assert(bitsel[0] < CHAR_BIT);
+		assert(bitsel[1] < CHAR_BIT);
+		index[0] = ((unsigned long) n >> bitsel[0]) & 0x1;
+		index[0] <<= 1;
+		index[1] = ((unsigned long) n >> bitsel[1]) & 0x1;
+		rindex = index[0] | index[1];
+		linear = (struct cds_ja_inode *) &node->u.data[rindex << type->pool_size_order];
+		break;
+	}
+	default:
+		linear = NULL;
+		assert(0);
+	}
+	return ja_linear_node_get_nth(type, linear, node_flag_ptr, n);
 }
 
 static
@@ -361,24 +492,117 @@ struct cds_ja_inode *ja_pool_node_get_ith_pool(const struct cds_ja_type *type,
 		&node->u.data[(unsigned int) i << type->pool_size_order];
 }
 
+static
+struct cds_ja_inode_flag *ja_pool_node_get_direction(const struct cds_ja_type *type,
+		struct cds_ja_inode *node,
+		int n, uint8_t *result_key,
+		enum ja_direction dir)
+{
+	unsigned int pool_nr;
+	int match_v;
+	struct cds_ja_inode_flag *match_node_flag = NULL;
+
+	assert(type->type_class == RCU_JA_POOL);
+	assert(dir == JA_LEFT || dir == JA_RIGHT);
+
+	if (dir == JA_LEFT) {
+		match_v = -1;
+	} else {
+		match_v = JA_ENTRY_PER_NODE;
+	}
+
+	for (pool_nr = 0; pool_nr < (1U << type->nr_pool_order); pool_nr++) {
+		struct cds_ja_inode *pool =
+			ja_pool_node_get_ith_pool(type,
+				node, pool_nr);
+		uint8_t nr_child =
+			ja_linear_node_get_nr_child(type, pool);
+		unsigned int j;
+
+		for (j = 0; j < nr_child; j++) {
+			struct cds_ja_inode_flag *iter;
+			uint8_t v;
+
+			ja_linear_node_get_ith_pos(type, pool,
+					j, &v, &iter);
+			if (!iter)
+				continue;
+			if (dir == JA_LEFT) {
+				if ((int) v < n && (int) v > match_v) {
+					match_v = v;
+					match_node_flag = iter;
+				}
+			} else {
+				if ((int) v > n && (int) v < match_v) {
+					match_v = v;
+					match_node_flag = iter;
+				}
+			}
+		}
+	}
+	if (match_node_flag)
+		*result_key = (uint8_t) match_v;
+	return match_node_flag;
+}
+
 static
 struct cds_ja_inode_flag *ja_pigeon_node_get_nth(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
-		struct cds_ja_inode_flag ***child_node_flag_ptr,
 		struct cds_ja_inode_flag ***node_flag_ptr,
 		uint8_t n)
 {
-	struct cds_ja_inode_flag **child_node_flag;
+	struct cds_ja_inode_flag **child_node_flag_ptr;
+	struct cds_ja_inode_flag *child_node_flag;
 
 	assert(type->type_class == RCU_JA_PIGEON);
-	child_node_flag = &((struct cds_ja_inode_flag **) node->u.data)[n];
+	child_node_flag_ptr = &((struct cds_ja_inode_flag **) node->u.data)[n];
+	child_node_flag = rcu_dereference(*child_node_flag_ptr);
 	dbg_printf("ja_pigeon_node_get_nth child_node_flag_ptr %p\n",
-		child_node_flag);
-	if (caa_unlikely(child_node_flag_ptr) && *child_node_flag)
-		*child_node_flag_ptr = child_node_flag;
+		child_node_flag_ptr);
 	if (caa_unlikely(node_flag_ptr))
-		*node_flag_ptr = child_node_flag;
-	return rcu_dereference(*child_node_flag);
+		*node_flag_ptr = child_node_flag_ptr;
+	return child_node_flag;
+}
+
+static
+struct cds_ja_inode_flag *ja_pigeon_node_get_direction(const struct cds_ja_type *type,
+		struct cds_ja_inode *node,
+		int n, uint8_t *result_key,
+		enum ja_direction dir)
+{
+	struct cds_ja_inode_flag **child_node_flag_ptr;
+	struct cds_ja_inode_flag *child_node_flag;
+	int i;
+
+	assert(type->type_class == RCU_JA_PIGEON);
+	assert(dir == JA_LEFT || dir == JA_RIGHT);
+
+	if (dir == JA_LEFT) {
+		/* n - 1 is first value left of n */
+		for (i = n - 1; i >= 0; i--) {
+			child_node_flag_ptr = &((struct cds_ja_inode_flag **) node->u.data)[i];
+			child_node_flag = rcu_dereference(*child_node_flag_ptr);
+			if (child_node_flag) {
+				dbg_printf("ja_pigeon_node_get_left child_node_flag %p\n",
+					child_node_flag);
+				*result_key = (uint8_t) i;
+				return child_node_flag;
+			}
+		}
+	} else {
+		/* n + 1 is first value right of n */
+		for (i = n + 1; i < JA_ENTRY_PER_NODE; i++) {
+			child_node_flag_ptr = &((struct cds_ja_inode_flag **) node->u.data)[i];
+			child_node_flag = rcu_dereference(*child_node_flag_ptr);
+			if (child_node_flag) {
+				dbg_printf("ja_pigeon_node_get_right child_node_flag %p\n",
+					child_node_flag);
+				*result_key = (uint8_t) i;
+				return child_node_flag;
+			}
+		}
+	}
+	return NULL;
 }
 
 static
@@ -386,7 +610,7 @@ struct cds_ja_inode_flag *ja_pigeon_node_get_ith_pos(const struct cds_ja_type *t
 		struct cds_ja_inode *node,
 		uint8_t i)
 {
-	return ja_pigeon_node_get_nth(type, node, NULL, NULL, i);
+	return ja_pigeon_node_get_nth(type, node, NULL, i);
 }
 
 /*
@@ -394,8 +618,7 @@ struct cds_ja_inode_flag *ja_pigeon_node_get_ith_pos(const struct cds_ja_type *t
  * node_flag is already rcu_dereference'd.
  */
 static
-struct cds_ja_inode_flag * ja_node_get_nth(struct cds_ja_inode_flag *node_flag,
-		struct cds_ja_inode_flag ***child_node_flag_ptr,
+struct cds_ja_inode_flag *ja_node_get_nth(struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_inode_flag ***node_flag_ptr,
 		uint8_t n)
 {
@@ -411,19 +634,71 @@ struct cds_ja_inode_flag * ja_node_get_nth(struct cds_ja_inode_flag *node_flag,
 	switch (type->type_class) {
 	case RCU_JA_LINEAR:
 		return ja_linear_node_get_nth(type, node,
-				child_node_flag_ptr, node_flag_ptr, n);
+				node_flag_ptr, n);
 	case RCU_JA_POOL:
-		return ja_pool_node_get_nth(type, node,
-				child_node_flag_ptr, node_flag_ptr, n);
+		return ja_pool_node_get_nth(type, node, node_flag,
+				node_flag_ptr, n);
 	case RCU_JA_PIGEON:
 		return ja_pigeon_node_get_nth(type, node,
-				child_node_flag_ptr, node_flag_ptr, n);
+				node_flag_ptr, n);
+	default:
+		assert(0);
+		return (void *) -1UL;
+	}
+}
+
+static
+struct cds_ja_inode_flag *ja_node_get_direction(struct cds_ja_inode_flag *node_flag,
+		int n, uint8_t *result_key,
+		enum ja_direction dir)
+{
+	unsigned int type_index;
+	struct cds_ja_inode *node;
+	const struct cds_ja_type *type;
+
+	node = ja_node_ptr(node_flag);
+	assert(node != NULL);
+	type_index = ja_node_type(node_flag);
+	type = &ja_types[type_index];
+
+	switch (type->type_class) {
+	case RCU_JA_LINEAR:
+		return ja_linear_node_get_direction(type, node, n, result_key, dir);
+	case RCU_JA_POOL:
+		return ja_pool_node_get_direction(type, node, n, result_key, dir);
+	case RCU_JA_PIGEON:
+		return ja_pigeon_node_get_direction(type, node, n, result_key, dir);
 	default:
 		assert(0);
 		return (void *) -1UL;
 	}
 }
 
+static
+struct cds_ja_inode_flag *ja_node_get_leftright(struct cds_ja_inode_flag *node_flag,
+		unsigned int n, uint8_t *result_key,
+		enum ja_direction dir)
+{
+	return ja_node_get_direction(node_flag, n, result_key, dir);
+}
+
+static
+struct cds_ja_inode_flag *ja_node_get_minmax(struct cds_ja_inode_flag *node_flag,
+		uint8_t *result_key,
+		enum ja_direction dir)
+{
+	switch (dir) {
+	case JA_LEFTMOST:
+		return ja_node_get_direction(node_flag,
+				-1, result_key, JA_RIGHT);
+	case JA_RIGHTMOST:
+		return ja_node_get_direction(node_flag,
+				JA_ENTRY_PER_NODE, result_key, JA_LEFT);
+	default:
+		assert(0);
+	}
+}
+
 static
 int ja_linear_node_set_nth(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
@@ -439,7 +714,8 @@ int ja_linear_node_set_nth(const struct cds_ja_type *type,
 	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
 
 	nr_child_ptr = &node->u.data[0];
-	dbg_printf("linear set nth: nr_child_ptr %p\n", nr_child_ptr);
+	dbg_printf("linear set nth: n %u, nr_child_ptr %p\n",
+		(unsigned int) n, nr_child_ptr);
 	nr_child = *nr_child_ptr;
 	assert(nr_child <= type->max_linear_child);
 
@@ -485,6 +761,7 @@ int ja_linear_node_set_nth(const struct cds_ja_type *type,
 static
 int ja_pool_node_set_nth(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
+		struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_shadow_node *shadow_node,
 		uint8_t n,
 		struct cds_ja_inode_flag *child_node_flag)
@@ -492,8 +769,37 @@ int ja_pool_node_set_nth(const struct cds_ja_type *type,
 	struct cds_ja_inode *linear;
 
 	assert(type->type_class == RCU_JA_POOL);
-	linear = (struct cds_ja_inode *)
-		&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
+
+	switch (type->nr_pool_order) {
+	case 1:
+	{
+		unsigned long bitsel, index;
+
+		bitsel = ja_node_pool_1d_bitsel(node_flag);
+		assert(bitsel < CHAR_BIT);
+		index = ((unsigned long) n >> bitsel) & 0x1;
+		linear = (struct cds_ja_inode *) &node->u.data[index << type->pool_size_order];
+		break;
+	}
+	case 2:
+	{
+		unsigned long bitsel[2], index[2], rindex;
+
+		ja_node_pool_2d_bitsel(node_flag, bitsel);
+		assert(bitsel[0] < CHAR_BIT);
+		assert(bitsel[1] < CHAR_BIT);
+		index[0] = ((unsigned long) n >> bitsel[0]) & 0x1;
+		index[0] <<= 1;
+		index[1] = ((unsigned long) n >> bitsel[1]) & 0x1;
+		rindex = index[0] | index[1];
+		linear = (struct cds_ja_inode *) &node->u.data[rindex << type->pool_size_order];
+		break;
+	}
+	default:
+		linear = NULL;
+		assert(0);
+	}
+
 	return ja_linear_node_set_nth(type, linear, shadow_node,
 			n, child_node_flag);
 }
@@ -523,6 +829,7 @@ int ja_pigeon_node_set_nth(const struct cds_ja_type *type,
 static
 int _ja_node_set_nth(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
+		struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_shadow_node *shadow_node,
 		uint8_t n,
 		struct cds_ja_inode_flag *child_node_flag)
@@ -532,7 +839,7 @@ int _ja_node_set_nth(const struct cds_ja_type *type,
 		return ja_linear_node_set_nth(type, node, shadow_node, n,
 				child_node_flag);
 	case RCU_JA_POOL:
-		return ja_pool_node_set_nth(type, node, shadow_node, n,
+		return ja_pool_node_set_nth(type, node, node_flag, shadow_node, n,
 				child_node_flag);
 	case RCU_JA_PIGEON:
 		return ja_pigeon_node_set_nth(type, node, shadow_node, n,
@@ -559,18 +866,17 @@ int ja_linear_node_clear_ptr(const struct cds_ja_type *type,
 	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
 
 	nr_child_ptr = &node->u.data[0];
-	dbg_printf("linear clear ptr: nr_child_ptr %p\n", nr_child_ptr);
 	nr_child = *nr_child_ptr;
 	assert(nr_child <= type->max_linear_child);
 
-	if (shadow_node->fallback_removal_count) {
-		shadow_node->fallback_removal_count--;
-	} else {
+	if (type->type_class == RCU_JA_LINEAR) {
+		assert(!shadow_node->fallback_removal_count);
 		if (shadow_node->nr_child <= type->min_child) {
 			/* We need to try recompacting the node */
 			return -EFBIG;
 		}
 	}
+	dbg_printf("linear clear ptr: nr_child_ptr %p\n", nr_child_ptr);
 	assert(*node_flag_ptr != NULL);
 	rcu_assign_pointer(*node_flag_ptr, NULL);
 	/*
@@ -585,13 +891,13 @@ int ja_linear_node_clear_ptr(const struct cds_ja_type *type,
 		(unsigned int) CMM_LOAD_SHARED(*nr_child_ptr),
 		(unsigned int) shadow_node->nr_child,
 		node, shadow_node);
-
 	return 0;
 }
 
 static
 int ja_pool_node_clear_ptr(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
+		struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_shadow_node *shadow_node,
 		struct cds_ja_inode_flag **node_flag_ptr,
 		uint8_t n)
@@ -599,8 +905,45 @@ int ja_pool_node_clear_ptr(const struct cds_ja_type *type,
 	struct cds_ja_inode *linear;
 
 	assert(type->type_class == RCU_JA_POOL);
-	linear = (struct cds_ja_inode *)
-		&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
+
+	if (shadow_node->fallback_removal_count) {
+		shadow_node->fallback_removal_count--;
+	} else {
+		/* We should try recompacting the node */
+		if (shadow_node->nr_child <= type->min_child)
+			return -EFBIG;
+	}
+
+	switch (type->nr_pool_order) {
+	case 1:
+	{
+		unsigned long bitsel, index;
+
+		bitsel = ja_node_pool_1d_bitsel(node_flag);
+		assert(bitsel < CHAR_BIT);
+		index = ((unsigned long) n >> bitsel) & type->nr_pool_order;
+		linear = (struct cds_ja_inode *) &node->u.data[index << type->pool_size_order];
+		break;
+	}
+	case 2:
+	{
+		unsigned long bitsel[2], index[2], rindex;
+
+		ja_node_pool_2d_bitsel(node_flag, bitsel);
+		assert(bitsel[0] < CHAR_BIT);
+		assert(bitsel[1] < CHAR_BIT);
+		index[0] = ((unsigned long) n >> bitsel[0]) & 0x1;
+		index[0] <<= 1;
+		index[1] = ((unsigned long) n >> bitsel[1]) & 0x1;
+		rindex = index[0] | index[1];
+		linear = (struct cds_ja_inode *) &node->u.data[rindex << type->pool_size_order];
+		break;
+	}
+	default:
+		linear = NULL;
+		assert(0);
+	}
+
 	return ja_linear_node_clear_ptr(type, linear, shadow_node, node_flag_ptr);
 }
 
@@ -611,6 +954,14 @@ int ja_pigeon_node_clear_ptr(const struct cds_ja_type *type,
 		struct cds_ja_inode_flag **node_flag_ptr)
 {
 	assert(type->type_class == RCU_JA_PIGEON);
+
+	if (shadow_node->fallback_removal_count) {
+		shadow_node->fallback_removal_count--;
+	} else {
+		/* We should try recompacting the node */
+		if (shadow_node->nr_child <= type->min_child)
+			return -EFBIG;
+	}
 	dbg_printf("ja_pigeon_node_clear_ptr: clearing ptr: %p\n", *node_flag_ptr);
 	rcu_assign_pointer(*node_flag_ptr, NULL);
 	shadow_node->nr_child--;
@@ -624,6 +975,7 @@ int ja_pigeon_node_clear_ptr(const struct cds_ja_type *type,
 static
 int _ja_node_clear_ptr(const struct cds_ja_type *type,
 		struct cds_ja_inode *node,
+		struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_shadow_node *shadow_node,
 		struct cds_ja_inode_flag **node_flag_ptr,
 		uint8_t n)
@@ -632,7 +984,7 @@ int _ja_node_clear_ptr(const struct cds_ja_type *type,
 	case RCU_JA_LINEAR:
 		return ja_linear_node_clear_ptr(type, node, shadow_node, node_flag_ptr);
 	case RCU_JA_POOL:
-		return ja_pool_node_clear_ptr(type, node, shadow_node, node_flag_ptr, n);
+		return ja_pool_node_clear_ptr(type, node, node_flag, shadow_node, node_flag_ptr, n);
 	case RCU_JA_PIGEON:
 		return ja_pigeon_node_clear_ptr(type, node, shadow_node, node_flag_ptr);
 	case RCU_JA_NULL:
@@ -646,105 +998,48 @@ int _ja_node_clear_ptr(const struct cds_ja_type *type,
 }
 
 /*
- * ja_node_recompact_add: recompact a node, adding a new child.
- * TODO: for pool type, take selection bit(s) into account.
- * Return 0 on success, -EAGAIN if need to retry, or other negative
- * error value otherwise.
+ * Calculate bit distribution. Returns the bit (0 to 7) that splits the
+ * distribution in two sub-distributions containing as much elements one
+ * compared to the other.
  */
 static
-int ja_node_recompact(enum ja_recompact mode,
+unsigned int ja_node_sum_distribution_1d(enum ja_recompact mode,
 		struct cds_ja *ja,
-		unsigned int old_type_index,
-		const struct cds_ja_type *old_type,
-		struct cds_ja_inode *old_node,
+		unsigned int type_index,
+		const struct cds_ja_type *type,
+		struct cds_ja_inode *node,
 		struct cds_ja_shadow_node *shadow_node,
-		struct cds_ja_inode_flag **old_node_flag_ptr, uint8_t n,
+		uint8_t n,
 		struct cds_ja_inode_flag *child_node_flag,
 		struct cds_ja_inode_flag **nullify_node_flag_ptr)
 {
-	unsigned int new_type_index;
-	struct cds_ja_inode *new_node;
-	struct cds_ja_shadow_node *new_shadow_node = NULL;
-	const struct cds_ja_type *new_type;
-	struct cds_ja_inode_flag *new_node_flag, *old_node_flag;
-	int ret;
-	int fallback = 0;
-
-	old_node_flag = *old_node_flag_ptr;
-
-	switch (mode) {
-	case JA_RECOMPACT:
-		new_type_index = old_type_index;
-		break;
-	case JA_RECOMPACT_ADD:
-		if (!shadow_node || old_type_index == NODE_INDEX_NULL) {
-			new_type_index = 0;
-		} else {
-			new_type_index = old_type_index + 1;
-		}
-		break;
-	case JA_RECOMPACT_DEL:
-		if (old_type_index == 0) {
-			new_type_index = NODE_INDEX_NULL;
-		} else {
-			new_type_index = old_type_index - 1;
-		}
-		break;
-	default:
-		assert(0);
-	}
-
-retry:		/* for fallback */
-	dbg_printf("Recompact from type %d to type %d\n",
-			old_type_index, new_type_index);
-	new_type = &ja_types[new_type_index];
-	if (new_type_index != NODE_INDEX_NULL) {
-		new_node = alloc_cds_ja_node(new_type);
-		if (!new_node)
-			return -ENOMEM;
-		new_node_flag = ja_node_flag(new_node, new_type_index);
-		dbg_printf("Recompact inherit lock from %p\n", shadow_node);
-		new_shadow_node = rcuja_shadow_set(ja->ht, new_node_flag, shadow_node, ja);
-		if (!new_shadow_node) {
-			free(new_node);
-			return -ENOMEM;
-		}
-		if (fallback)
-			new_shadow_node->fallback_removal_count =
-						JA_FALLBACK_REMOVAL_COUNT;
-	} else {
-		new_node = NULL;
-		new_node_flag = NULL;
-	}
-
-	assert(mode != JA_RECOMPACT_ADD || old_type->type_class != RCU_JA_PIGEON);
+	uint8_t nr_one[JA_BITS_PER_BYTE];
+	unsigned int bitsel = 0, bit_i, overall_best_distance = UINT_MAX;
+	unsigned int distrib_nr_child = 0;
 
-	if (new_type_index == NODE_INDEX_NULL)
-		goto skip_copy;
+	memset(nr_one, 0, sizeof(nr_one));
 
-	switch (old_type->type_class) {
+	switch (type->type_class) {
 	case RCU_JA_LINEAR:
 	{
 		uint8_t nr_child =
-			ja_linear_node_get_nr_child(old_type, old_node);
+			ja_linear_node_get_nr_child(type, node);
 		unsigned int i;
 
 		for (i = 0; i < nr_child; i++) {
 			struct cds_ja_inode_flag *iter;
 			uint8_t v;
 
-			ja_linear_node_get_ith_pos(old_type, old_node, i, &v, &iter);
+			ja_linear_node_get_ith_pos(type, node, i, &v, &iter);
 			if (!iter)
 				continue;
 			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
 				continue;
-			ret = _ja_node_set_nth(new_type, new_node,
-					new_shadow_node,
-					v, iter);
-			if (new_type->type_class == RCU_JA_POOL && ret) {
-				goto fallback_toosmall;
+			for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+				if (v & (1U << bit_i))
+					nr_one[bit_i]++;
 			}
-			assert(!ret);
+			distrib_nr_child++;
 		}
 		break;
 	}
@@ -752,12 +1047,493 @@ retry:		/* for fallback */
 	{
 		unsigned int pool_nr;
 
-		for (pool_nr = 0; pool_nr < (1U << old_type->nr_pool_order); pool_nr++) {
+		for (pool_nr = 0; pool_nr < (1U << type->nr_pool_order); pool_nr++) {
 			struct cds_ja_inode *pool =
-				ja_pool_node_get_ith_pool(old_type,
-					old_node, pool_nr);
+				ja_pool_node_get_ith_pool(type,
+					node, pool_nr);
 			uint8_t nr_child =
-				ja_linear_node_get_nr_child(old_type, pool);
+				ja_linear_node_get_nr_child(type, pool);
+			unsigned int j;
+
+			for (j = 0; j < nr_child; j++) {
+				struct cds_ja_inode_flag *iter;
+				uint8_t v;
+
+				ja_linear_node_get_ith_pos(type, pool,
+						j, &v, &iter);
+				if (!iter)
+					continue;
+				if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
+					continue;
+				for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+					if (v & (1U << bit_i))
+						nr_one[bit_i]++;
+				}
+				distrib_nr_child++;
+			}
+		}
+		break;
+	}
+	case RCU_JA_PIGEON:
+	{
+		unsigned int i;
+
+		assert(mode == JA_RECOMPACT_DEL);
+		for (i = 0; i < JA_ENTRY_PER_NODE; i++) {
+			struct cds_ja_inode_flag *iter;
+
+			iter = ja_pigeon_node_get_ith_pos(type, node, i);
+			if (!iter)
+				continue;
+			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
+				continue;
+			for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+				if (i & (1U << bit_i))
+					nr_one[bit_i]++;
+			}
+			distrib_nr_child++;
+		}
+		break;
+	}
+	case RCU_JA_NULL:
+		assert(mode == JA_RECOMPACT_ADD_NEXT);
+		break;
+	default:
+		assert(0);
+		break;
+	}
+
+	if (mode == JA_RECOMPACT_ADD_NEXT || mode == JA_RECOMPACT_ADD_SAME) {
+		for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+			if (n & (1U << bit_i))
+				nr_one[bit_i]++;
+		}
+		distrib_nr_child++;
+	}
+
+	/*
+	 * The best bit selector is that for which the number of ones is
+	 * closest to half of the number of children in the
+	 * distribution. We calculate the distance using the double of
+	 * the sub-distribution sizes to eliminate truncation error.
+	 */
+	for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+		unsigned int distance_to_best;
+
+		distance_to_best = abs_int(((unsigned int) nr_one[bit_i] << 1U) - distrib_nr_child);
+		if (distance_to_best < overall_best_distance) {
+			overall_best_distance = distance_to_best;
+			bitsel = bit_i;
+		}
+	}
+	dbg_printf("1 dimension pool bit selection: (%u)\n", bitsel);
+	return bitsel;
+}
+
+/*
+ * Calculate bit distribution in two dimensions. Returns the two bits
+ * (each 0 to 7) that splits the distribution in four sub-distributions
+ * containing as much elements one compared to the other.
+ */
+static
+void ja_node_sum_distribution_2d(enum ja_recompact mode,
+		struct cds_ja *ja,
+		unsigned int type_index,
+		const struct cds_ja_type *type,
+		struct cds_ja_inode *node,
+		struct cds_ja_shadow_node *shadow_node,
+		uint8_t n,
+		struct cds_ja_inode_flag *child_node_flag,
+		struct cds_ja_inode_flag **nullify_node_flag_ptr,
+		unsigned int *_bitsel)
+{
+	uint8_t nr_2d_11[JA_BITS_PER_BYTE][JA_BITS_PER_BYTE],
+		nr_2d_10[JA_BITS_PER_BYTE][JA_BITS_PER_BYTE],
+		nr_2d_01[JA_BITS_PER_BYTE][JA_BITS_PER_BYTE],
+		nr_2d_00[JA_BITS_PER_BYTE][JA_BITS_PER_BYTE];
+	unsigned int bitsel[2] = { 0, 1 };
+	unsigned int bit_i, bit_j;
+	int overall_best_distance = INT_MAX;
+	unsigned int distrib_nr_child = 0;
+
+	memset(nr_2d_11, 0, sizeof(nr_2d_11));
+	memset(nr_2d_10, 0, sizeof(nr_2d_10));
+	memset(nr_2d_01, 0, sizeof(nr_2d_01));
+	memset(nr_2d_00, 0, sizeof(nr_2d_00));
+
+	switch (type->type_class) {
+	case RCU_JA_LINEAR:
+	{
+		uint8_t nr_child =
+			ja_linear_node_get_nr_child(type, node);
+		unsigned int i;
+
+		for (i = 0; i < nr_child; i++) {
+			struct cds_ja_inode_flag *iter;
+			uint8_t v;
+
+			ja_linear_node_get_ith_pos(type, node, i, &v, &iter);
+			if (!iter)
+				continue;
+			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
+				continue;
+			for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+				for (bit_j = 0; bit_j < bit_i; bit_j++) {
+					if (v & (1U << bit_i)) {
+						if (v & (1U << bit_j)) {
+							nr_2d_11[bit_i][bit_j]++;
+						} else {
+							nr_2d_10[bit_i][bit_j]++;
+						}
+					} else {
+						if (v & (1U << bit_j)) {
+							nr_2d_01[bit_i][bit_j]++;
+						} else {
+							nr_2d_00[bit_i][bit_j]++;
+						}
+					}
+				}
+			}
+			distrib_nr_child++;
+		}
+		break;
+	}
+	case RCU_JA_POOL:
+	{
+		unsigned int pool_nr;
+
+		for (pool_nr = 0; pool_nr < (1U << type->nr_pool_order); pool_nr++) {
+			struct cds_ja_inode *pool =
+				ja_pool_node_get_ith_pool(type,
+					node, pool_nr);
+			uint8_t nr_child =
+				ja_linear_node_get_nr_child(type, pool);
+			unsigned int j;
+
+			for (j = 0; j < nr_child; j++) {
+				struct cds_ja_inode_flag *iter;
+				uint8_t v;
+
+				ja_linear_node_get_ith_pos(type, pool,
+						j, &v, &iter);
+				if (!iter)
+					continue;
+				if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
+					continue;
+				for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+					for (bit_j = 0; bit_j < bit_i; bit_j++) {
+						if (v & (1U << bit_i)) {
+							if (v & (1U << bit_j)) {
+								nr_2d_11[bit_i][bit_j]++;
+							} else {
+								nr_2d_10[bit_i][bit_j]++;
+							}
+						} else {
+							if (v & (1U << bit_j)) {
+								nr_2d_01[bit_i][bit_j]++;
+							} else {
+								nr_2d_00[bit_i][bit_j]++;
+							}
+						}
+					}
+				}
+				distrib_nr_child++;
+			}
+		}
+		break;
+	}
+	case RCU_JA_PIGEON:
+	{
+		unsigned int i;
+
+		assert(mode == JA_RECOMPACT_DEL);
+		for (i = 0; i < JA_ENTRY_PER_NODE; i++) {
+			struct cds_ja_inode_flag *iter;
+
+			iter = ja_pigeon_node_get_ith_pos(type, node, i);
+			if (!iter)
+				continue;
+			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
+				continue;
+			for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+				for (bit_j = 0; bit_j < bit_i; bit_j++) {
+					if (i & (1U << bit_i)) {
+						if (i & (1U << bit_j)) {
+							nr_2d_11[bit_i][bit_j]++;
+						} else {
+							nr_2d_10[bit_i][bit_j]++;
+						}
+					} else {
+						if (i & (1U << bit_j)) {
+							nr_2d_01[bit_i][bit_j]++;
+						} else {
+							nr_2d_00[bit_i][bit_j]++;
+						}
+					}
+				}
+			}
+			distrib_nr_child++;
+		}
+		break;
+	}
+	case RCU_JA_NULL:
+		assert(mode == JA_RECOMPACT_ADD_NEXT);
+		break;
+	default:
+		assert(0);
+		break;
+	}
+
+	if (mode == JA_RECOMPACT_ADD_NEXT || mode == JA_RECOMPACT_ADD_SAME) {
+		for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+			for (bit_j = 0; bit_j < bit_i; bit_j++) {
+				if (n & (1U << bit_i)) {
+					if (n & (1U << bit_j)) {
+						nr_2d_11[bit_i][bit_j]++;
+					} else {
+						nr_2d_10[bit_i][bit_j]++;
+					}
+				} else {
+					if (n & (1U << bit_j)) {
+						nr_2d_01[bit_i][bit_j]++;
+					} else {
+						nr_2d_00[bit_i][bit_j]++;
+					}
+				}
+			}
+		}
+		distrib_nr_child++;
+	}
+
+	/*
+	 * The best bit selector is that for which the number of nodes
+	 * in each sub-class is closest to one-fourth of the number of
+	 * children in the distribution. We calculate the distance using
+	 * 4 times the size of the sub-distribution to eliminate
+	 * truncation error.
+	 */
+	for (bit_i = 0; bit_i < JA_BITS_PER_BYTE; bit_i++) {
+		for (bit_j = 0; bit_j < bit_i; bit_j++) {
+			int distance_to_best[4];
+
+			distance_to_best[0] = ((unsigned int) nr_2d_11[bit_i][bit_j] << 2U) - distrib_nr_child;
+			distance_to_best[1] = ((unsigned int) nr_2d_10[bit_i][bit_j] << 2U) - distrib_nr_child;
+			distance_to_best[2] = ((unsigned int) nr_2d_01[bit_i][bit_j] << 2U) - distrib_nr_child;
+			distance_to_best[3] = ((unsigned int) nr_2d_00[bit_i][bit_j] << 2U) - distrib_nr_child;
+
+			/* Consider worse distance above best */
+			if (distance_to_best[1] > 0 && distance_to_best[1] > distance_to_best[0])
+				distance_to_best[0] = distance_to_best[1];
+			if (distance_to_best[2] > 0 && distance_to_best[2] > distance_to_best[0])
+				distance_to_best[0] = distance_to_best[2];
+			if (distance_to_best[3] > 0 && distance_to_best[3] > distance_to_best[0])
+				distance_to_best[0] = distance_to_best[3];
+
+			/*
+			 * If our worse distance is better than overall,
+			 * we become new best candidate.
+			 */
+			if (distance_to_best[0] < overall_best_distance) {
+				overall_best_distance = distance_to_best[0];
+				bitsel[0] = bit_i;
+				bitsel[1] = bit_j;
+			}
+		}
+	}
+
+	dbg_printf("2 dimensions pool bit selection: (%u,%u)\n", bitsel[0], bitsel[1]);
+
+	/* Return our bit selection */
+	_bitsel[0] = bitsel[0];
+	_bitsel[1] = bitsel[1];
+}
+
+static
+unsigned int find_nearest_type_index(unsigned int type_index,
+		unsigned int nr_nodes)
+{
+	const struct cds_ja_type *type;
+
+	assert(type_index != NODE_INDEX_NULL);
+	if (nr_nodes == 0)
+		return NODE_INDEX_NULL;
+	for (;;) {
+		type = &ja_types[type_index];
+		if (nr_nodes < type->min_child)
+			type_index--;
+		else if (nr_nodes > type->max_child)
+			type_index++;
+		else
+			break;
+	}
+	return type_index;
+}
+
+/*
+ * ja_node_recompact_add: recompact a node, adding a new child.
+ * Return 0 on success, -EAGAIN if need to retry, or other negative
+ * error value otherwise.
+ */
+static
+int ja_node_recompact(enum ja_recompact mode,
+		struct cds_ja *ja,
+		unsigned int old_type_index,
+		const struct cds_ja_type *old_type,
+		struct cds_ja_inode *old_node,
+		struct cds_ja_shadow_node *shadow_node,
+		struct cds_ja_inode_flag **old_node_flag_ptr, uint8_t n,
+		struct cds_ja_inode_flag *child_node_flag,
+		struct cds_ja_inode_flag **nullify_node_flag_ptr,
+		int level)
+{
+	unsigned int new_type_index;
+	struct cds_ja_inode *new_node;
+	struct cds_ja_shadow_node *new_shadow_node = NULL;
+	const struct cds_ja_type *new_type;
+	struct cds_ja_inode_flag *new_node_flag, *old_node_flag;
+	int ret;
+	int fallback = 0;
+
+	old_node_flag = *old_node_flag_ptr;
+
+	/*
+	 * Need to find nearest type index even for ADD_SAME, because
+	 * this recompaction, when applied to linear nodes, will garbage
+	 * collect dummy (NULL) entries, and can therefore cause a few
+	 * linear representations to be skipped.
+	 */
+	switch (mode) {
+	case JA_RECOMPACT_ADD_SAME:
+		new_type_index = find_nearest_type_index(old_type_index,
+			shadow_node->nr_child + 1);
+		dbg_printf("Recompact for node with %u children\n",
+			shadow_node->nr_child + 1);
+		break;
+	case JA_RECOMPACT_ADD_NEXT:
+		if (!shadow_node || old_type_index == NODE_INDEX_NULL) {
+			new_type_index = 0;
+			dbg_printf("Recompact for NULL\n");
+		} else {
+			new_type_index = find_nearest_type_index(old_type_index,
+				shadow_node->nr_child + 1);
+			dbg_printf("Recompact for node with %u children\n",
+				shadow_node->nr_child + 1);
+		}
+		break;
+	case JA_RECOMPACT_DEL:
+		new_type_index = find_nearest_type_index(old_type_index,
+			shadow_node->nr_child - 1);
+		dbg_printf("Recompact for node with %u children\n",
+			shadow_node->nr_child - 1);
+		break;
+	default:
+		assert(0);
+	}
+
+retry:		/* for fallback */
+	dbg_printf("Recompact from type %d to type %d\n",
+			old_type_index, new_type_index);
+	new_type = &ja_types[new_type_index];
+	if (new_type_index != NODE_INDEX_NULL) {
+		new_node = alloc_cds_ja_node(ja, new_type);
+		if (!new_node)
+			return -ENOMEM;
+
+		if (new_type->type_class == RCU_JA_POOL) {
+			switch (new_type->nr_pool_order) {
+			case 1:
+			{
+				unsigned int node_distrib_bitsel;
+
+				node_distrib_bitsel =
+					ja_node_sum_distribution_1d(mode, ja,
+						old_type_index, old_type,
+						old_node, shadow_node,
+						n, child_node_flag,
+						nullify_node_flag_ptr);
+				assert(!((unsigned long) new_node & JA_POOL_1D_MASK));
+				new_node_flag = ja_node_flag_pool_1d(new_node,
+					new_type_index, node_distrib_bitsel);
+				break;
+			}
+			case 2:
+			{
+				unsigned int node_distrib_bitsel[2];
+
+				ja_node_sum_distribution_2d(mode, ja,
+					old_type_index, old_type,
+					old_node, shadow_node,
+					n, child_node_flag,
+					nullify_node_flag_ptr,
+					node_distrib_bitsel);
+				assert(!((unsigned long) new_node & JA_POOL_1D_MASK));
+				assert(!((unsigned long) new_node & JA_POOL_2D_MASK));
+				new_node_flag = ja_node_flag_pool_2d(new_node,
+					new_type_index, node_distrib_bitsel);
+				break;
+			}
+			default:
+				assert(0);
+			}
+		} else {
+			new_node_flag = ja_node_flag(new_node, new_type_index);
+		}
+
+		dbg_printf("Recompact inherit lock from %p\n", shadow_node);
+		new_shadow_node = rcuja_shadow_set(ja->ht, new_node_flag, shadow_node, ja, level);
+		if (!new_shadow_node) {
+			free_cds_ja_node(ja, new_node);
+			return -ENOMEM;
+		}
+		if (fallback)
+			new_shadow_node->fallback_removal_count =
+						JA_FALLBACK_REMOVAL_COUNT;
+	} else {
+		new_node = NULL;
+		new_node_flag = NULL;
+	}
+
+	assert(mode != JA_RECOMPACT_ADD_NEXT || old_type->type_class != RCU_JA_PIGEON);
+
+	if (new_type_index == NODE_INDEX_NULL)
+		goto skip_copy;
+
+	switch (old_type->type_class) {
+	case RCU_JA_LINEAR:
+	{
+		uint8_t nr_child =
+			ja_linear_node_get_nr_child(old_type, old_node);
+		unsigned int i;
+
+		for (i = 0; i < nr_child; i++) {
+			struct cds_ja_inode_flag *iter;
+			uint8_t v;
+
+			ja_linear_node_get_ith_pos(old_type, old_node, i, &v, &iter);
+			if (!iter)
+				continue;
+			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
+				continue;
+			ret = _ja_node_set_nth(new_type, new_node, new_node_flag,
+					new_shadow_node,
+					v, iter);
+			if (new_type->type_class == RCU_JA_POOL && ret) {
+				goto fallback_toosmall;
+			}
+			assert(!ret);
+		}
+		break;
+	}
+	case RCU_JA_POOL:
+	{
+		unsigned int pool_nr;
+
+		for (pool_nr = 0; pool_nr < (1U << old_type->nr_pool_order); pool_nr++) {
+			struct cds_ja_inode *pool =
+				ja_pool_node_get_ith_pool(old_type,
+					old_node, pool_nr);
+			uint8_t nr_child =
+				ja_linear_node_get_nr_child(old_type, pool);
 			unsigned int j;
 
 			for (j = 0; j < nr_child; j++) {
@@ -770,7 +1546,7 @@ retry:		/* for fallback */
 					continue;
 				if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
 					continue;
-				ret = _ja_node_set_nth(new_type, new_node,
+				ret = _ja_node_set_nth(new_type, new_node, new_node_flag,
 						new_shadow_node,
 						v, iter);
 				if (new_type->type_class == RCU_JA_POOL
@@ -783,16 +1559,14 @@ retry:		/* for fallback */
 		break;
 	}
 	case RCU_JA_NULL:
-		assert(mode == JA_RECOMPACT_ADD);
+		assert(mode == JA_RECOMPACT_ADD_NEXT);
 		break;
 	case RCU_JA_PIGEON:
 	{
-		uint8_t nr_child;
 		unsigned int i;
 
 		assert(mode == JA_RECOMPACT_DEL);
-		nr_child = shadow_node->nr_child;
-		for (i = 0; i < nr_child; i++) {
+		for (i = 0; i < JA_ENTRY_PER_NODE; i++) {
 			struct cds_ja_inode_flag *iter;
 
 			iter = ja_pigeon_node_get_ith_pos(old_type, old_node, i);
@@ -800,7 +1574,7 @@ retry:		/* for fallback */
 				continue;
 			if (mode == JA_RECOMPACT_DEL && *nullify_node_flag_ptr == iter)
 				continue;
-			ret = _ja_node_set_nth(new_type, new_node,
+			ret = _ja_node_set_nth(new_type, new_node, new_node_flag,
 					new_shadow_node,
 					i, iter);
 			if (new_type->type_class == RCU_JA_POOL && ret) {
@@ -817,13 +1591,25 @@ retry:		/* for fallback */
 	}
 skip_copy:
 
-	if (mode == JA_RECOMPACT_ADD) {
+	if (mode == JA_RECOMPACT_ADD_NEXT || mode == JA_RECOMPACT_ADD_SAME) {
 		/* add node */
-		ret = _ja_node_set_nth(new_type, new_node,
+		ret = _ja_node_set_nth(new_type, new_node, new_node_flag,
 				new_shadow_node,
 				n, child_node_flag);
+		if (new_type->type_class == RCU_JA_POOL && ret) {
+			goto fallback_toosmall;
+		}
 		assert(!ret);
 	}
+
+	if (fallback) {
+		dbg_printf("Using fallback for %u children, node type index: %u, mode %s\n",
+			new_shadow_node->nr_child, old_type_index, mode == JA_RECOMPACT_ADD_NEXT ? "add_next" :
+				(mode == JA_RECOMPACT_DEL ? "del" : "add_same"));
+		if (ja_debug_counters())
+			uatomic_inc(&ja->node_fallback_count_distribution[new_shadow_node->nr_child]);
+	}
+
 	/* Return pointer to new recompacted node through old_node_flag_ptr */
 	*old_node_flag_ptr = new_node_flag;
 	if (old_node) {
@@ -836,7 +1622,7 @@ skip_copy:
 		 * This synchronizes removal with re-add of that node.
 		 */
 		if (new_type_index == NODE_INDEX_NULL)
-			flags = RCUJA_SHADOW_CLEAR_FREE_LOCK;
+			flags |= RCUJA_SHADOW_CLEAR_FREE_LOCK;
 		ret = rcuja_shadow_clear(ja->ht, old_node_flag, shadow_node,
 				flags);
 		assert(!ret);
@@ -853,7 +1639,70 @@ fallback_toosmall:
 			RCUJA_SHADOW_CLEAR_FREE_NODE);
 	assert(!ret);
 
-	/* Choose fallback type: pigeon */
+	switch (mode) {
+	case JA_RECOMPACT_ADD_SAME:
+		/*
+		 * JA_RECOMPACT_ADD_SAME is only triggered if a linear
+		 * node within a pool has unused entries. It should
+		 * therefore _never_ be too small.
+		 */
+		assert(0);
+
+		/* Fall-through */
+	case JA_RECOMPACT_ADD_NEXT:
+	{
+		const struct cds_ja_type *next_type;
+
+		/*
+		 * Recompaction attempt on add failed. Should only
+		 * happen if target node type is pool. Caused by
+		 * hard-to-split distribution. Recompact using the next
+		 * distribution size.
+		 */
+		assert(new_type->type_class == RCU_JA_POOL);
+		next_type = &ja_types[new_type_index + 1];
+		/*
+		 * Try going to the next pool size if our population
+		 * fits within its range. This is not flagged as a
+		 * fallback.
+		 */
+		if (shadow_node->nr_child + 1 >= next_type->min_child
+				&& shadow_node->nr_child + 1 <= next_type->max_child) {
+			new_type_index++;
+			goto retry;
+		} else {
+			new_type_index++;
+			dbg_printf("Add fallback to type %d\n", new_type_index);
+			if (ja_debug_counters())
+				uatomic_inc(&ja->nr_fallback);
+			fallback = 1;
+			goto retry;
+		}
+		break;
+	}
+	case JA_RECOMPACT_DEL:
+		/*
+		 * Recompaction attempt on delete failed. Should only
+		 * happen if target node type is pool. This is caused by
+		 * a hard-to-split distribution. Recompact on same node
+		 * size, but flag current node as "fallback" to ensure
+		 * we don't attempt recompaction before some activity
+		 * has reshuffled our node.
+		 */
+		assert(new_type->type_class == RCU_JA_POOL);
+		new_type_index = old_type_index;
+		dbg_printf("Delete fallback keeping type %d\n", new_type_index);
+		uatomic_inc(&ja->nr_fallback);
+		fallback = 1;
+		goto retry;
+	default:
+		assert(0);
+		return -EINVAL;
+	}
+
+	/*
+	 * Last resort fallback: pigeon.
+	 */
 	new_type_index = (1UL << JA_TYPE_BITS) - 1;
 	dbg_printf("Fallback to type %d\n", new_type_index);
 	uatomic_inc(&ja->nr_fallback);
@@ -869,7 +1718,8 @@ static
 int ja_node_set_nth(struct cds_ja *ja,
 		struct cds_ja_inode_flag **node_flag, uint8_t n,
 		struct cds_ja_inode_flag *child_node_flag,
-		struct cds_ja_shadow_node *shadow_node)
+		struct cds_ja_shadow_node *shadow_node,
+		int level)
 {
 	int ret;
 	unsigned int type_index;
@@ -882,18 +1732,18 @@ int ja_node_set_nth(struct cds_ja *ja,
 	node = ja_node_ptr(*node_flag);
 	type_index = ja_node_type(*node_flag);
 	type = &ja_types[type_index];
-	ret = _ja_node_set_nth(type, node, shadow_node,
+	ret = _ja_node_set_nth(type, node, *node_flag, shadow_node,
 			n, child_node_flag);
 	switch (ret) {
 	case -ENOSPC:
-		/* Not enough space in node, need to recompact. */
-		ret = ja_node_recompact(JA_RECOMPACT_ADD, ja, type_index, type, node,
-				shadow_node, node_flag, n, child_node_flag, NULL);
+		/* Not enough space in node, need to recompact to next type. */
+		ret = ja_node_recompact(JA_RECOMPACT_ADD_NEXT, ja, type_index, type, node,
+				shadow_node, node_flag, n, child_node_flag, NULL, level);
 		break;
 	case -ERANGE:
 		/* Node needs to be recompacted. */
-		ret = ja_node_recompact(JA_RECOMPACT, ja, type_index, type, node,
-				shadow_node, node_flag, n, child_node_flag, NULL);
+		ret = ja_node_recompact(JA_RECOMPACT_ADD_SAME, ja, type_index, type, node,
+				shadow_node, node_flag, n, child_node_flag, NULL, level);
 		break;
 	}
 	return ret;
@@ -908,7 +1758,7 @@ int ja_node_clear_ptr(struct cds_ja *ja,
 		struct cds_ja_inode_flag **node_flag_ptr,	/* Pointer to location to nullify */
 		struct cds_ja_inode_flag **parent_node_flag_ptr,	/* Address of parent ptr in its parent */
 		struct cds_ja_shadow_node *shadow_node,		/* of parent */
-		uint8_t n)
+		uint8_t n, int level)
 {
 	int ret;
 	unsigned int type_index;
@@ -921,46 +1771,189 @@ int ja_node_clear_ptr(struct cds_ja *ja,
 	node = ja_node_ptr(*parent_node_flag_ptr);
 	type_index = ja_node_type(*parent_node_flag_ptr);
 	type = &ja_types[type_index];
-	ret = _ja_node_clear_ptr(type, node, shadow_node, node_flag_ptr, n);
+	ret = _ja_node_clear_ptr(type, node, *parent_node_flag_ptr, shadow_node, node_flag_ptr, n);
 	if (ret == -EFBIG) {
-		/* Should to try recompaction. */
+		/* Should try recompaction. */
 		ret = ja_node_recompact(JA_RECOMPACT_DEL, ja, type_index, type, node,
 				shadow_node, parent_node_flag_ptr, n, NULL,
-				node_flag_ptr);
+				node_flag_ptr, level);
 	}
 	return ret;
 }
 
-struct cds_hlist_head cds_ja_lookup(struct cds_ja *ja, uint64_t key)
+struct cds_ja_node *cds_ja_lookup(struct cds_ja *ja, uint64_t key)
+{
+	unsigned int tree_depth, i;
+	struct cds_ja_inode_flag *node_flag;
+
+	if (caa_unlikely(key > ja->key_max || key == UINT64_MAX))
+		return NULL;
+	tree_depth = ja->tree_depth;
+	node_flag = rcu_dereference(ja->root);
+
+	/* level 0: root node */
+	if (!ja_node_ptr(node_flag))
+		return NULL;
+
+	for (i = 1; i < tree_depth; i++) {
+		uint8_t iter_key;
+
+		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - i - 1)));
+		node_flag = ja_node_get_nth(node_flag, NULL, iter_key);
+		dbg_printf("cds_ja_lookup iter key lookup %u finds node_flag %p\n",
+				(unsigned int) iter_key, node_flag);
+		if (!ja_node_ptr(node_flag))
+			return NULL;
+	}
+
+	/* Last level lookup succeded. We got an actual match. */
+	return (struct cds_ja_node *) node_flag;
+}
+
+static
+struct cds_ja_node *cds_ja_lookup_inequality(struct cds_ja *ja, uint64_t key,
+		uint64_t *result_key, enum ja_lookup_inequality mode)
 {
-	unsigned int tree_depth, i;
-	struct cds_ja_inode_flag *node_flag;
-	struct cds_hlist_head head = { NULL };
+	int tree_depth, level;
+	struct cds_ja_inode_flag *node_flag, *cur_node_depth[JA_MAX_DEPTH];
+	uint8_t cur_key[JA_MAX_DEPTH];
+	uint64_t _result_key = 0;
+	enum ja_direction dir;
+
+	switch (mode) {
+	case JA_LOOKUP_BE:
+	case JA_LOOKUP_AE:
+		if (caa_unlikely(key > ja->key_max || key == UINT64_MAX))
+			return NULL;
+		break;
+	default:
+		return NULL;
+	}
 
-	if (caa_unlikely(key > ja->key_max))
-		return head;
+	memset(cur_node_depth, 0, sizeof(cur_node_depth));
+	memset(cur_key, 0, sizeof(cur_key));
 	tree_depth = ja->tree_depth;
 	node_flag = rcu_dereference(ja->root);
+	cur_node_depth[0] = node_flag;
 
 	/* level 0: root node */
 	if (!ja_node_ptr(node_flag))
-		return head;
+		return NULL;
 
-	for (i = 1; i < tree_depth; i++) {
+	for (level = 1; level < tree_depth; level++) {
 		uint8_t iter_key;
 
-		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - i - 1)));
-		node_flag = ja_node_get_nth(node_flag, NULL, NULL,
-			iter_key);
-		dbg_printf("cds_ja_lookup iter key lookup %u finds node_flag %p\n",
+		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - level - 1)));
+		node_flag = ja_node_get_nth(node_flag, NULL, iter_key);
+		if (!ja_node_ptr(node_flag))
+			break;
+		cur_key[level - 1] = iter_key;
+		cur_node_depth[level] = node_flag;
+		dbg_printf("cds_ja_lookup_inequality iter key lookup %u finds node_flag %p\n",
 				(unsigned int) iter_key, node_flag);
+	}
+
+	if (level == tree_depth) {
+		/* Last level lookup succeded. We got an equal match. */
+		if (result_key)
+			*result_key = key;
+		return (struct cds_ja_node *) node_flag;
+	}
+
+	/*
+	 * Find highest value left/right of current node.
+	 * Current node is cur_node_depth[level].
+	 * Start at current level. If we cannot find any key left/right
+	 * of ours, go one level up, seek highest value left/right of
+	 * current (recursively), and when we find one, get the
+	 * rightmost/leftmost child of its rightmost/leftmost child
+	 * (recursively).
+	 */
+	switch (mode) {
+	case JA_LOOKUP_BE:
+		dir = JA_LEFT;
+		break;
+	case JA_LOOKUP_AE:
+		dir = JA_RIGHT;
+		break;
+	default:
+		assert(0);
+	}
+	for (; level > 0; level--) {
+		uint8_t iter_key;
+
+		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - level - 1)));
+		node_flag = ja_node_get_leftright(cur_node_depth[level - 1],
+				iter_key, &cur_key[level - 1], dir);
+		dbg_printf("cds_ja_lookup_inequality find sibling from %u at %u finds node_flag %p\n",
+				(unsigned int) iter_key, (unsigned int) cur_key[level - 1],
+				node_flag);
+		/* If found left/right sibling, find rightmost/leftmost child. */
+		if (ja_node_ptr(node_flag))
+			break;
+	}
+
+	if (!level) {
+		/* Reached the root and could not find a left/right sibling. */
+		return NULL;
+	}
+
+	level++;
+
+	/*
+	 * From this point, we are guaranteed to be able to find a
+	 * "below than"/"above than" match. ja_attach_node() and
+	 * ja_detach_node() both guarantee that it is not possible for a
+	 * lookup to reach a dead-end.
+	 */
+
+	/*
+	 * Find rightmost/leftmost child of rightmost/leftmost child
+	 * (recursively).
+	 */
+	switch (mode) {
+	case JA_LOOKUP_BE:
+		dir = JA_RIGHTMOST;
+		break;
+	case JA_LOOKUP_AE:
+		dir = JA_LEFTMOST;
+		break;
+	default:
+		assert(0);
+	}
+	for (; level < tree_depth; level++) {
+		node_flag = ja_node_get_minmax(node_flag, &cur_key[level - 1], dir);
+		dbg_printf("cds_ja_lookup_inequality find minmax at %u finds node_flag %p\n",
+				(unsigned int) cur_key[level - 1],
+				node_flag);
 		if (!ja_node_ptr(node_flag))
-			return head;
+			break;
 	}
 
-	/* Last level lookup succeded. We got an actual match. */
-	head.next = (struct cds_hlist_node *) node_flag;
-	return head;
+	assert(level == tree_depth);
+
+	if (result_key) {
+		for (level = 1; level < tree_depth; level++) {
+			_result_key |= ((uint64_t) cur_key[level - 1])
+					<< (JA_BITS_PER_BYTE * (tree_depth - level - 1));
+		}
+		*result_key = _result_key;
+	}
+	return (struct cds_ja_node *) node_flag;
+}
+
+struct cds_ja_node *cds_ja_lookup_below_equal(struct cds_ja *ja,
+		uint64_t key, uint64_t *result_key)
+{
+	dbg_printf("cds_ja_lookup_below_equal key %" PRIu64 "\n", key);
+	return cds_ja_lookup_inequality(ja, key, result_key, JA_LOOKUP_BE);
+}
+
+struct cds_ja_node *cds_ja_lookup_above_equal(struct cds_ja *ja,
+		uint64_t key, uint64_t *result_key)
+{
+	dbg_printf("cds_ja_lookup_above_equal key %" PRIu64 "\n", key);
+	return cds_ja_lookup_inequality(ja, key, result_key, JA_LOOKUP_AE);
 }
 
 /*
@@ -974,98 +1967,144 @@ struct cds_hlist_head cds_ja_lookup(struct cds_ja *ja, uint64_t key)
  * parent lock (if needed).  Then we can proceed to create the new
  * branch. Publish the new branch, and release locks.
  * TODO: we currently always take the parent lock even when not needed.
+ *
+ * ja_attach_node() ensures that a lookup will _never_ see a branch that
+ * leads to a dead-end: before attaching a branch, the entire content of
+ * the new branch is populated, thus creating a cluster, before
+ * attaching the cluster to the rest of the tree, thus making it visible
+ * to lookups.
  */
 static
 int ja_attach_node(struct cds_ja *ja,
 		struct cds_ja_inode_flag **attach_node_flag_ptr,
-		struct cds_ja_inode_flag **node_flag_ptr,
-		struct cds_ja_inode_flag *node_flag,
-		struct cds_ja_inode_flag *parent_node_flag,
+		struct cds_ja_inode_flag *attach_node_flag,
+		struct cds_ja_inode_flag *parent_attach_node_flag,
+		struct cds_ja_inode_flag **old_node_flag_ptr,
+		struct cds_ja_inode_flag *old_node_flag,
 		uint64_t key,
 		unsigned int level,
 		struct cds_ja_node *child_node)
 {
 	struct cds_ja_shadow_node *shadow_node = NULL,
 			*parent_shadow_node = NULL;
-	struct cds_ja_inode *node = ja_node_ptr(node_flag);
-	struct cds_ja_inode *parent_node = ja_node_ptr(parent_node_flag);
-	struct cds_hlist_head head;
 	struct cds_ja_inode_flag *iter_node_flag, *iter_dest_node_flag;
 	int ret, i;
 	struct cds_ja_inode_flag *created_nodes[JA_MAX_DEPTH];
 	int nr_created_nodes = 0;
 
-	dbg_printf("Attach node at level %u (node %p, node_flag %p)\n",
-		level, node, node_flag);
+	dbg_printf("Attach node at level %u (old_node_flag %p, attach_node_flag_ptr %p attach_node_flag %p, parent_attach_node_flag %p)\n",
+		level, old_node_flag, attach_node_flag_ptr, attach_node_flag, parent_attach_node_flag);
 
-	assert(node);
-	shadow_node = rcuja_shadow_lookup_lock(ja->ht, node_flag);
-	if (!shadow_node) {
-		ret = -EAGAIN;
-		goto end;
+	assert(!old_node_flag);
+	if (attach_node_flag) {
+		shadow_node = rcuja_shadow_lookup_lock(ja->ht, attach_node_flag);
+		if (!shadow_node) {
+			ret = -EAGAIN;
+			goto end;
+		}
 	}
-	if (parent_node) {
+	if (parent_attach_node_flag) {
 		parent_shadow_node = rcuja_shadow_lookup_lock(ja->ht,
-						parent_node_flag);
+						parent_attach_node_flag);
 		if (!parent_shadow_node) {
 			ret = -EAGAIN;
 			goto unlock_shadow;
 		}
 	}
 
-	if (node_flag_ptr && ja_node_ptr(*node_flag_ptr)) {
+	if (old_node_flag_ptr && ja_node_ptr(*old_node_flag_ptr)) {
+		/*
+		 * Target node has been updated between RCU lookup and
+		 * lock acquisition. We need to re-try lookup and
+		 * attach.
+		 */
+		ret = -EAGAIN;
+		goto unlock_parent;
+	}
+
+	/*
+	 * Perform a lookup query to handle the case where
+	 * old_node_flag_ptr is NULL. We cannot use it to check if the
+	 * node has been populated between RCU lookup and mutex
+	 * acquisition.
+	 */
+	if (!old_node_flag_ptr) {
+		uint8_t iter_key;
+		struct cds_ja_inode_flag *lookup_node_flag;
+		struct cds_ja_inode_flag **lookup_node_flag_ptr;
+
+		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (ja->tree_depth - level)));
+		lookup_node_flag = ja_node_get_nth(attach_node_flag,
+			&lookup_node_flag_ptr,
+			iter_key);
+		if (lookup_node_flag) {
+			ret = -EEXIST;
+			goto unlock_parent;
+		}
+	}
+
+	if (attach_node_flag_ptr && ja_node_ptr(*attach_node_flag_ptr) !=
+			ja_node_ptr(attach_node_flag)) {
 		/*
-		 * Target node is non-NULL: it has been updated between
-		 * RCU lookup and lock acquisition. We need to re-try
-		 * lookup and attach.
+		 * Target node has been updated between RCU lookup and
+		 * lock acquisition. We need to re-try lookup and
+		 * attach.
 		 */
 		ret = -EAGAIN;
 		goto unlock_parent;
 	}
 
 	/* Create new branch, starting from bottom */
-	CDS_INIT_HLIST_HEAD(&head);
-	cds_hlist_add_head_rcu(&child_node->list, &head);
-	iter_node_flag = (struct cds_ja_inode_flag *) head.next;
+	iter_node_flag = (struct cds_ja_inode_flag *) child_node;
 
-	for (i = ja->tree_depth; i > (int) level; i--) {
+	for (i = ja->tree_depth - 1; i >= (int) level; i--) {
 		uint8_t iter_key;
 
-		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (ja->tree_depth - i)));
+		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (ja->tree_depth - i - 1)));
 		dbg_printf("branch creation level %d, key %u\n",
-				i - 1, (unsigned int) iter_key);
+				i, (unsigned int) iter_key);
 		iter_dest_node_flag = NULL;
 		ret = ja_node_set_nth(ja, &iter_dest_node_flag,
 			iter_key,
 			iter_node_flag,
-			NULL);
-		if (ret)
+			NULL, i);
+		if (ret) {
+			dbg_printf("branch creation error %d\n", ret);
 			goto check_error;
+		}
 		created_nodes[nr_created_nodes++] = iter_dest_node_flag;
 		iter_node_flag = iter_dest_node_flag;
 	}
+	assert(level > 0);
 
-	if (level > 1) {
+	/* Publish branch */
+	if (level == 1) {
+		/*
+		 * Attaching to root node.
+		 */
+		rcu_assign_pointer(ja->root, iter_node_flag);
+	} else {
 		uint8_t iter_key;
 
 		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (ja->tree_depth - level)));
+		dbg_printf("publish branch at level %d, key %u\n",
+				level - 1, (unsigned int) iter_key);
 		/* We need to use set_nth on the previous level. */
-		iter_dest_node_flag = node_flag;
+		iter_dest_node_flag = attach_node_flag;
 		ret = ja_node_set_nth(ja, &iter_dest_node_flag,
 			iter_key,
 			iter_node_flag,
-			shadow_node);
-		if (ret)
+			shadow_node, level - 1);
+		if (ret) {
+			dbg_printf("branch publish error %d\n", ret);
 			goto check_error;
-		created_nodes[nr_created_nodes++] = iter_dest_node_flag;
-		iter_node_flag = iter_dest_node_flag;
+		}
+		/*
+		 * Attach branch
+		 */
+		rcu_assign_pointer(*attach_node_flag_ptr, iter_dest_node_flag);
 	}
 
-	/* Publish new branch */
-	dbg_printf("Publish branch %p, replacing %p\n",
-		iter_node_flag, *attach_node_flag_ptr);
-	rcu_assign_pointer(*attach_node_flag_ptr, iter_node_flag);
-
 	/* Success */
 	ret = 0;
 
@@ -1096,113 +2135,175 @@ end:
 }
 
 /*
- * Lock the parent containing the hlist head pointer, and add node to list of
- * duplicates. Failure can happen if concurrent update changes the
- * parent before we get the lock. We return -EAGAIN in that case.
+ * Lock the parent containing the pointer to list of duplicates, and add
+ * node to this list. Failure can happen if concurrent update changes
+ * the parent before we get the lock. We return -EAGAIN in that case.
  * Return 0 on success, negative error value on failure.
  */
 static
 int ja_chain_node(struct cds_ja *ja,
 		struct cds_ja_inode_flag *parent_node_flag,
 		struct cds_ja_inode_flag **node_flag_ptr,
-		struct cds_hlist_head *head,
+		struct cds_ja_inode_flag *node_flag,
+		struct cds_ja_node *last_node,
 		struct cds_ja_node *node)
 {
 	struct cds_ja_shadow_node *shadow_node;
-	int ret = 0;
+	struct cds_ja_node *iter_node;
+	int ret = 0, found = 0;
 
 	shadow_node = rcuja_shadow_lookup_lock(ja->ht, parent_node_flag);
 	if (!shadow_node) {
 		return -EAGAIN;
 	}
-	if (!ja_node_ptr(*node_flag_ptr)) {
+	/*
+	 * Ensure that previous node is still there at end of list.
+	 */
+	iter_node = (struct cds_ja_node *) ja_node_ptr(node_flag);
+	if ((struct cds_ja_node *) ja_node_ptr(*node_flag_ptr) != iter_node) {
+		ret = -EAGAIN;
+		goto end;
+	}
+	cds_ja_for_each_duplicate(iter_node) {
+		if (iter_node == last_node)
+			found = 1;
+	}
+	if (!found) {
 		ret = -EAGAIN;
 		goto end;
 	}
-	cds_hlist_add_head_rcu(&node->list, head);
+	/*
+	 * Add node to tail of list to ensure that RCU traversals will
+	 * always see either the prior node or the newly added if
+	 * executed concurrently with a sequence of add followed by del
+	 * on the same key. Safe against concurrent RCU read traversals.
+	 */
+	node->next = NULL;
+	rcu_assign_pointer(last_node->next, node);
 end:
 	rcuja_shadow_unlock(shadow_node);
 	return ret;
 }
 
-int cds_ja_add(struct cds_ja *ja, uint64_t key,
-		struct cds_ja_node *new_node)
+static
+int _cds_ja_add(struct cds_ja *ja, uint64_t key,
+		struct cds_ja_node *node,
+		struct cds_ja_node **unique_node_ret)
 {
 	unsigned int tree_depth, i;
+	struct cds_ja_inode_flag *attach_node_flag,
+		*parent_node_flag,
+		*parent2_node_flag,
+		*node_flag,
+		*parent_attach_node_flag;
 	struct cds_ja_inode_flag **attach_node_flag_ptr,
+		**parent_node_flag_ptr,
 		**node_flag_ptr;
-	struct cds_ja_inode_flag *node_flag,
-		*parent_node_flag,
-		*parent2_node_flag;
 	int ret;
 
-	if (caa_unlikely(key > ja->key_max)) {
+	if (caa_unlikely(key > ja->key_max || key == UINT64_MAX)) {
 		return -EINVAL;
 	}
 	tree_depth = ja->tree_depth;
 
 retry:
 	dbg_printf("cds_ja_add attempt: key %" PRIu64 ", node %p\n",
-		key, new_node);
+		key, node);
 	parent2_node_flag = NULL;
 	parent_node_flag =
 		(struct cds_ja_inode_flag *) &ja->root;	/* Use root ptr address as key for mutex */
-	attach_node_flag_ptr = &ja->root;
-	node_flag_ptr = &ja->root;
+	parent_node_flag_ptr = NULL;
 	node_flag = rcu_dereference(ja->root);
+	node_flag_ptr = &ja->root;
 
 	/* Iterate on all internal levels */
 	for (i = 1; i < tree_depth; i++) {
 		uint8_t iter_key;
 
-		dbg_printf("cds_ja_add iter attach_node_flag_ptr %p node_flag_ptr %p node_flag %p\n",
-				*attach_node_flag_ptr, *node_flag_ptr, node_flag);
-		if (!ja_node_ptr(node_flag)) {
-			ret = ja_attach_node(ja, attach_node_flag_ptr,
-					node_flag_ptr,
-					parent_node_flag, parent2_node_flag,
-					key, i, new_node);
-			if (ret == -EAGAIN || ret == -EEXIST)
-				goto retry;
-			else
-				goto end;
-		}
+		if (!ja_node_ptr(node_flag))
+			break;
+		dbg_printf("cds_ja_add iter parent2_node_flag %p parent_node_flag %p node_flag_ptr %p node_flag %p\n",
+				parent2_node_flag, parent_node_flag, node_flag_ptr, node_flag);
 		iter_key = (uint8_t) (key >> (JA_BITS_PER_BYTE * (tree_depth - i - 1)));
 		parent2_node_flag = parent_node_flag;
 		parent_node_flag = node_flag;
+		parent_node_flag_ptr = node_flag_ptr;
 		node_flag = ja_node_get_nth(node_flag,
-			&attach_node_flag_ptr,
 			&node_flag_ptr,
 			iter_key);
-		dbg_printf("cds_ja_add iter key lookup %u finds node_flag %p attach_node_flag_ptr %p node_flag_ptr %p\n",
-				(unsigned int) iter_key, node_flag,
-				*attach_node_flag_ptr,
-				*node_flag_ptr);
 	}
 
 	/*
-	 * We reached bottom of tree, simply add node to last internal
-	 * level, or chain it if key is already present.
+	 * We reached either bottom of tree or internal NULL node,
+	 * simply add node to last internal level, or chain it if key is
+	 * already present.
 	 */
 	if (!ja_node_ptr(node_flag)) {
-		dbg_printf("cds_ja_add last attach_node_flag_ptr %p node_flag_ptr %p node_flag %p\n",
-				*attach_node_flag_ptr, *node_flag_ptr, node_flag);
+		dbg_printf("cds_ja_add NULL parent2_node_flag %p parent_node_flag %p node_flag_ptr %p node_flag %p\n",
+				parent2_node_flag, parent_node_flag, node_flag_ptr, node_flag);
+
+		attach_node_flag = parent_node_flag;
+		attach_node_flag_ptr = parent_node_flag_ptr;
+		parent_attach_node_flag = parent2_node_flag;
+
 		ret = ja_attach_node(ja, attach_node_flag_ptr,
-				node_flag_ptr, parent_node_flag,
-				parent2_node_flag, key, i, new_node);
+				attach_node_flag,
+				parent_attach_node_flag,
+				node_flag_ptr,
+				node_flag,
+				key, i, node);
 	} else {
+		struct cds_ja_node *iter_node, *last_node = NULL;
+
+		if (unique_node_ret) {
+			*unique_node_ret = (struct cds_ja_node *) ja_node_ptr(node_flag);
+			return -EEXIST;
+		}
+
+		/* Find last duplicate */
+		iter_node = (struct cds_ja_node *) ja_node_ptr(node_flag);
+		cds_ja_for_each_duplicate_rcu(iter_node)
+			last_node = iter_node;
+
+		dbg_printf("cds_ja_add duplicate parent2_node_flag %p parent_node_flag %p node_flag_ptr %p node_flag %p\n",
+				parent2_node_flag, parent_node_flag, node_flag_ptr, node_flag);
+
+		attach_node_flag = node_flag;
+		attach_node_flag_ptr = node_flag_ptr;
+		parent_attach_node_flag = parent_node_flag;
+
 		ret = ja_chain_node(ja,
-			parent_node_flag,
-			node_flag_ptr,
-			(struct cds_hlist_head *) attach_node_flag_ptr,
-			new_node);
+			parent_attach_node_flag,
+			attach_node_flag_ptr,
+			attach_node_flag,
+			last_node,
+			node);
 	}
 	if (ret == -EAGAIN || ret == -EEXIST)
 		goto retry;
-end:
+
 	return ret;
 }
 
+int cds_ja_add(struct cds_ja *ja, uint64_t key,
+		struct cds_ja_node *node)
+{
+	return _cds_ja_add(ja, key, node, NULL);
+}
+
+struct cds_ja_node *cds_ja_add_unique(struct cds_ja *ja, uint64_t key,
+		struct cds_ja_node *node)
+{
+	int ret;
+	struct cds_ja_node *ret_node;
+
+	ret = _cds_ja_add(ja, key, node, &ret_node);
+	if (ret == -EEXIST)
+		return ret_node;
+	else
+		return node;
+}
+
 /*
  * Note: there is no need to lookup the pointer address associated with
  * each node's nth item after taking the lock: it's already been done by
@@ -1213,6 +2314,11 @@ end:
  * However, when a child is removed from "linear" nodes, its pointer
  * is set to NULL. We therefore check, while holding the locks, if this
  * pointer is NULL, and return -ENOENT to the caller if it is the case.
+ *
+ * ja_detach_node() ensures that a lookup will _never_ see a branch that
+ * leads to a dead-end: when removing branch, it makes sure to perform
+ * the "cut" at the highest node that has only one child, effectively
+ * replacing it with a NULL pointer.
  */
 static
 int ja_detach_node(struct cds_ja *ja,
@@ -1249,8 +2355,20 @@ int ja_detach_node(struct cds_ja *ja,
 			ret = -EAGAIN;
 			goto end;
 		}
-		assert(shadow_node->nr_child > 0);
 		shadow_nodes[nr_shadow++] = shadow_node;
+
+		/*
+		 * Check if node has been removed between RCU
+		 * lookup and lock acquisition.
+		 */
+		assert(snapshot_ptr[i + 1]);
+		if (ja_node_ptr(*snapshot_ptr[i + 1])
+				!= ja_node_ptr(snapshot[i + 1])) {
+			ret = -ENOENT;
+			goto end;
+		}
+
+		assert(shadow_node->nr_child > 0);
 		if (shadow_node->nr_child == 1 && i > 1)
 			nr_clear++;
 		nr_branch++;
@@ -1263,10 +2381,23 @@ int ja_detach_node(struct cds_ja *ja,
 				goto end;
 			}
 			shadow_nodes[nr_shadow++] = shadow_node;
+
+			/*
+			 * Check if node has been removed between RCU
+			 * lookup and lock acquisition.
+			 */
+			assert(snapshot_ptr[i]);
+			if (ja_node_ptr(*snapshot_ptr[i])
+					!= ja_node_ptr(snapshot[i])) {
+				ret = -ENOENT;
+				goto end;
+			}
+
 			node_flag_ptr = snapshot_ptr[i + 1];
 			n = snapshot_n[i + 1];
 			parent_node_flag_ptr = snapshot_ptr[i];
 			parent_node_flag = snapshot[i];
+
 			if (i > 1) {
 				/*
 				 * Lock parent's parent, in case we need
@@ -1279,27 +2410,29 @@ int ja_detach_node(struct cds_ja *ja,
 					goto end;
 				}
 				shadow_nodes[nr_shadow++] = shadow_node;
+
+				/*
+				 * Check if node has been removed between RCU
+				 * lookup and lock acquisition.
+				 */
+				assert(snapshot_ptr[i - 1]);
+				if (ja_node_ptr(*snapshot_ptr[i - 1])
+						!= ja_node_ptr(snapshot[i - 1])) {
+					ret = -ENOENT;
+					goto end;
+				}
 			}
+
 			break;
 		}
 	}
 
-	/*
-	 * Check if node has been removed between RCU lookup and lock
-	 * acquisition.
-	 */
-	assert(node_flag_ptr);
-	if (!ja_node_ptr(*node_flag_ptr)) {
-		ret = -ENOENT;
-		goto end;
-	}
-
 	/*
 	 * At this point, we want to delete all nodes that are about to
 	 * be removed from shadow_nodes (except the last one, which is
 	 * either the root or the parent of the upmost node with 1
-	 * child). OK to as to free lock here, because RCU read lock is
-	 * held, and free only performed in call_rcu.
+	 * child). OK to free lock here, because RCU read lock is held,
+	 * and free only performed in call_rcu.
 	 */
 
 	for (i = 0; i < nr_clear; i++) {
@@ -1317,7 +2450,7 @@ int ja_detach_node(struct cds_ja *ja,
 		node_flag_ptr, 		/* Pointer to location to nullify */
 		&iter_node_flag,	/* Old new parent ptr in its parent */
 		shadow_nodes[nr_branch - 1],	/* of parent */
-		n);
+		n, nr_branch - 1);
 	if (ret)
 		goto end;
 
@@ -1336,33 +2469,48 @@ static
 int ja_unchain_node(struct cds_ja *ja,
 		struct cds_ja_inode_flag *parent_node_flag,
 		struct cds_ja_inode_flag **node_flag_ptr,
-		struct cds_hlist_head *head,
+		struct cds_ja_inode_flag *node_flag,
 		struct cds_ja_node *node)
 {
 	struct cds_ja_shadow_node *shadow_node;
-	struct cds_hlist_node *hlist_node;
-	int ret = 0, count = 0;
+	struct cds_ja_node *iter_node, **iter_node_ptr, **prev_node_ptr = NULL;
+	int ret = 0, count = 0, found = 0;
 
 	shadow_node = rcuja_shadow_lookup_lock(ja->ht, parent_node_flag);
 	if (!shadow_node)
 		return -EAGAIN;
-	if (!ja_node_ptr(*node_flag_ptr)) {
+	if (ja_node_ptr(*node_flag_ptr) != ja_node_ptr(node_flag)) {
 		ret = -EAGAIN;
 		goto end;
 	}
 	/*
-	 * Retry if another thread removed all but one of duplicates
-	 * since check (this check was performed without lock).
+	 * Find the previous node's next pointer pointing to our node,
+	 * so we can update it. Retry if another thread removed all but
+	 * one of duplicates since check (this check was performed
+	 * without lock). Ensure that the node we are about to remove is
+	 * still in the list (while holding lock). No need for RCU
+	 * traversal here since we hold the lock on the parent.
 	 */
-	cds_hlist_for_each_rcu(hlist_node, head, list) {
+	iter_node_ptr = (struct cds_ja_node **) node_flag_ptr;
+	iter_node = (struct cds_ja_node *) ja_node_ptr(node_flag);
+	cds_ja_for_each_duplicate(iter_node) {
 		count++;
+		if (iter_node == node) {
+			prev_node_ptr = iter_node_ptr;
+			found++;
+		}
+		iter_node_ptr = &iter_node->next;
 	}
-
-	if (count == 1) {
+	assert(found <= 1);
+	if (!found || count == 1) {
 		ret = -EAGAIN;
 		goto end;
 	}
-	cds_hlist_del_rcu(&node->list);
+	CMM_STORE_SHARED(*prev_node_ptr, node->next);
+	/*
+	 * Validate that we indeed removed the node from linked list.
+	 */
+	assert(ja_node_ptr(*node_flag_ptr) != (struct cds_ja_inode *) node);
 end:
 	rcuja_shadow_unlock(shadow_node);
 	return ret;
@@ -1384,7 +2532,7 @@ int cds_ja_del(struct cds_ja *ja, uint64_t key,
 	int nr_snapshot;
 	int ret;
 
-	if (caa_unlikely(key > ja->key_max))
+	if (caa_unlikely(key > ja->key_max || key == UINT64_MAX))
 		return -EINVAL;
 	tree_depth = ja->tree_depth;
 
@@ -1416,14 +2564,14 @@ retry:
 		snapshot_ptr[nr_snapshot] = prev_node_flag_ptr;
 		snapshot[nr_snapshot++] = node_flag;
 		node_flag = ja_node_get_nth(node_flag,
-			&prev_node_flag_ptr,
 			&node_flag_ptr,
 			iter_key);
+		if (node_flag)
+			prev_node_flag_ptr = node_flag_ptr;
 		dbg_printf("cds_ja_del iter key lookup %u finds node_flag %p, prev_node_flag_ptr %p\n",
 				(unsigned int) iter_key, node_flag,
 				prev_node_flag_ptr);
 	}
-
 	/*
 	 * We reached bottom of tree, try to find the node we are trying
 	 * to remove. Fail if we cannot find it.
@@ -1433,22 +2581,17 @@ retry:
 				key);
 		return -ENOENT;
 	} else {
-		struct cds_hlist_head hlist_head;
-		struct cds_hlist_node *hlist_node;
-		struct cds_ja_node *entry, *match = NULL;
+		struct cds_ja_node *iter_node, *match = NULL;
 		int count = 0;
 
-		hlist_head.next =
-			(struct cds_hlist_node *) ja_node_ptr(node_flag);
-		cds_hlist_for_each_entry_rcu(entry,
-				hlist_node,
-				&hlist_head,
-				list) {
-			dbg_printf("cds_ja_del: compare %p with entry %p\n", node, entry);
-			if (entry == node)
-				match = entry;
+		iter_node = (struct cds_ja_node *) ja_node_ptr(node_flag);
+		cds_ja_for_each_duplicate_rcu(iter_node) {
+			dbg_printf("cds_ja_del: compare %p with iter_node %p\n", node, iter_node);
+			if (iter_node == node)
+				match = iter_node;
 			count++;
 		}
+
 		if (!match) {
 			dbg_printf("cds_ja_del: no node match for node %p key %" PRIu64 "\n", node, key);
 			return -ENOENT;
@@ -1465,7 +2608,7 @@ retry:
 					snapshot_n, nr_snapshot, key, node);
 		} else {
 			ret = ja_unchain_node(ja, snapshot[nr_snapshot - 1],
-				node_flag_ptr, &hlist_head, match);
+				node_flag_ptr, node_flag, match);
 		}
 	}
 	/*
@@ -1519,12 +2662,11 @@ struct cds_ja *_cds_ja_new(unsigned int key_bits,
 	 */
 	root_shadow_node = rcuja_shadow_set(ja->ht,
 			(struct cds_ja_inode_flag *) &ja->root,
-			NULL, ja);
+			NULL, ja, 0);
 	if (!root_shadow_node) {
 		ret = -ENOMEM;
 		goto ht_node_error;
 	}
-	root_shadow_node->level = 0;
 
 	return ja;
 
@@ -1538,126 +2680,76 @@ ja_error:
 	return NULL;
 }
 
-/*
- * Called from RCU read-side CS.
- */
-__attribute__((visibility("protected")))
-void rcuja_free_all_children(struct cds_ja_shadow_node *shadow_node,
-		struct cds_ja_inode_flag *node_flag,
-		void (*free_node_cb)(struct rcu_head *head))
+static
+void print_debug_fallback_distribution(struct cds_ja *ja)
 {
-	const struct rcu_flavor_struct *flavor;
-	unsigned int type_index;
-	struct cds_ja_inode *node;
-	const struct cds_ja_type *type;
-
-	flavor = cds_lfht_rcu_flavor(shadow_node->ja->ht);
-	node = ja_node_ptr(node_flag);
-	assert(node != NULL);
-	type_index = ja_node_type(node_flag);
-	type = &ja_types[type_index];
-
-	switch (type->type_class) {
-	case RCU_JA_LINEAR:
-	{
-		uint8_t nr_child =
-			ja_linear_node_get_nr_child(type, node);
-		unsigned int i;
-
-		for (i = 0; i < nr_child; i++) {
-			struct cds_ja_inode_flag *iter;
-			struct cds_hlist_head head;
-			struct cds_ja_node *entry;
-			struct cds_hlist_node *pos;
-			uint8_t v;
-
-			ja_linear_node_get_ith_pos(type, node, i, &v, &iter);
-			if (!iter)
-				continue;
-			head.next = (struct cds_hlist_node *) iter;
-			cds_hlist_for_each_entry_rcu(entry, pos, &head, list) {
-				flavor->update_call_rcu(&entry->head, free_node_cb);
-			}
-		}
-		break;
+	int i;
+
+	fprintf(stderr, "Fallback node distribution:\n");
+	for (i = 0; i < JA_ENTRY_PER_NODE; i++) {
+		if (!ja->node_fallback_count_distribution[i])
+			continue;
+		fprintf(stderr, "	%3u: %4lu\n",
+			i, ja->node_fallback_count_distribution[i]);
 	}
-	case RCU_JA_POOL:
-	{
-		unsigned int pool_nr;
-
-		for (pool_nr = 0; pool_nr < (1U << type->nr_pool_order); pool_nr++) {
-			struct cds_ja_inode *pool =
-				ja_pool_node_get_ith_pool(type, node, pool_nr);
-			uint8_t nr_child =
-				ja_linear_node_get_nr_child(type, pool);
-			unsigned int j;
-
-			for (j = 0; j < nr_child; j++) {
-				struct cds_ja_inode_flag *iter;
-				struct cds_hlist_head head;
-				struct cds_ja_node *entry;
-				struct cds_hlist_node *pos;
-				uint8_t v;
+}
 
-				ja_linear_node_get_ith_pos(type, node, j, &v, &iter);
-				if (!iter)
-					continue;
-				head.next = (struct cds_hlist_node *) iter;
-				cds_hlist_for_each_entry_rcu(entry, pos, &head, list) {
-					flavor->update_call_rcu(&entry->head, free_node_cb);
-				}
-			}
-		}
-		break;
-	}
-	case RCU_JA_NULL:
-		break;
-	case RCU_JA_PIGEON:
-	{
-		uint8_t nr_child;
-		unsigned int i;
+static
+int ja_final_checks(struct cds_ja *ja)
+{
+	double fallback_ratio;
+	unsigned long na, nf, nr_fallback;
+	int ret = 0;
 
-		nr_child = shadow_node->nr_child;
-		for (i = 0; i < nr_child; i++) {
-			struct cds_ja_inode_flag *iter;
-			struct cds_hlist_head head;
-			struct cds_ja_node *entry;
-			struct cds_hlist_node *pos;
+	if (!ja_debug_counters())
+		return 0;
 
-			iter = ja_pigeon_node_get_ith_pos(type, node, i);
-			if (!iter)
-				continue;
-			head.next = (struct cds_hlist_node *) iter;
-			cds_hlist_for_each_entry_rcu(entry, pos, &head, list) {
-				flavor->update_call_rcu(&entry->head, free_node_cb);
-			}
-		}
-		break;
-	}
-	default:
-		assert(0);
+	fallback_ratio = (double) uatomic_read(&ja->nr_fallback);
+	fallback_ratio /= (double) uatomic_read(&ja->nr_nodes_allocated);
+	nr_fallback = uatomic_read(&ja->nr_fallback);
+	if (nr_fallback)
+		fprintf(stderr,
+			"[warning] RCU Judy Array used %lu fallback node(s) (ratio: %g)\n",
+			uatomic_read(&ja->nr_fallback),
+			fallback_ratio);
+
+	na = uatomic_read(&ja->nr_nodes_allocated);
+	nf = uatomic_read(&ja->nr_nodes_freed);
+	dbg_printf("Nodes allocated: %lu, Nodes freed: %lu.\n", na, nf);
+	if (nr_fallback)
+		print_debug_fallback_distribution(ja);
+
+	if (na != nf) {
+		fprintf(stderr, "[error] Judy array leaked %ld nodes. Allocated: %lu, freed: %lu.\n",
+			(long) na - nf, na, nf);
+		ret = -1;
 	}
+	return ret;
 }
 
 /*
- * There should be no more concurrent add to the judy array while it is
- * being destroyed (ensured by the caller).
+ * There should be no more concurrent add, delete, nor look-up performed
+ * on the Judy array while it is being destroyed (ensured by the
+ * caller).
  */
-int cds_ja_destroy(struct cds_ja *ja,
-		void (*free_node_cb)(struct rcu_head *head))
+int cds_ja_destroy(struct cds_ja *ja)
 {
+	const struct rcu_flavor_struct *flavor;
 	int ret;
 
+	flavor = cds_lfht_rcu_flavor(ja->ht);
 	rcuja_shadow_prune(ja->ht,
-		RCUJA_SHADOW_CLEAR_FREE_NODE | RCUJA_SHADOW_CLEAR_FREE_LOCK,
-		free_node_cb);
+		RCUJA_SHADOW_CLEAR_FREE_NODE | RCUJA_SHADOW_CLEAR_FREE_LOCK);
+	flavor->thread_offline();
 	ret = rcuja_delete_ht(ja->ht);
 	if (ret)
 		return ret;
-	if (uatomic_read(&ja->nr_fallback))
-		fprintf(stderr,
-			"[warning] RCU Judy Array used %lu fallback node(s)\n",
-			uatomic_read(&ja->nr_fallback));
+
+	/* Wait for in-flight call_rcu free to complete. */
+	flavor->barrier();
+
+	flavor->thread_online();
+	ret = ja_final_checks(ja);
 	free(ja);
-	return 0;
+	return ret;
 }