X-Git-Url: http://git.lttng.org./?a=blobdiff_plain;f=rcuja%2Frcuja.c;h=27661fe204bdfda17270914cd862d58c23cd819b;hb=335d8b1825b5eebf4281a46bd2029394edb06314;hp=6dcd9c63d5f87b154ff96e03787364b5badf8612;hpb=61009379872b40dbd0d69bb3baaf82e55ec58b39;p=userspace-rcu.git

diff --git a/rcuja/rcuja.c b/rcuja/rcuja.c
index 6dcd9c6..27661fe 100644
--- a/rcuja/rcuja.c
+++ b/rcuja/rcuja.c
@@ -20,6 +20,664 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+#define _LGPL_SOURCE
+#include <stdint.h>
+#include <errno.h>
+#include <limits.h>
 #include <urcu/rcuja.h>
+#include <urcu/compiler.h>
+#include <urcu/arch.h>
+#include <assert.h>
+#include <urcu-pointer.h>
+
 #include "rcuja-internal.h"
+#include "bitfield.h"
+
+enum rcu_ja_type_class {
+	RCU_JA_LINEAR = 0,	/* Type A */
+			/* 32-bit: 1 to 25 children, 8 to 128 bytes */
+			/* 64-bit: 1 to 28 children, 16 to 256 bytes */
+	RCU_JA_POOL = 1,	/* Type B */
+			/* 32-bit: 26 to 100 children, 256 to 512 bytes */
+			/* 64-bit: 29 to 112 children, 512 to 1024 bytes */
+	RCU_JA_PIGEON = 2,	/* Type C */
+			/* 32-bit: 101 to 256 children, 1024 bytes */
+			/* 64-bit: 113 to 256 children, 2048 bytes */
+	/* Leaf nodes are implicit from their height in the tree */
+	RCU_JA_NR_TYPES,
+
+	RCU_JA_NULL,	/* not an encoded type, but keeps code regular */
+};
+
+struct rcu_ja_type {
+	enum rcu_ja_type_class type_class;
+	uint16_t min_child;		/* minimum number of children: 1 to 256 */
+	uint16_t max_child;		/* maximum number of children: 1 to 256 */
+	uint16_t max_linear_child;	/* per-pool max nr. children: 1 to 256 */
+	uint16_t order;			/* node size is (1 << order), in bytes */
+	uint16_t nr_pool_order;		/* number of pools */
+	uint16_t pool_size_order;	/* pool size */
+};
+
+/*
+ * Number of least significant pointer bits reserved to represent the
+ * child type.
+ */
+#define JA_TYPE_BITS	3
+#define JA_TYPE_MAX_NR	(1U << JA_TYPE_BITS)
+#define JA_TYPE_MASK	(JA_TYPE_MAX_NR - 1)
+#define JA_PTR_MASK	(~JA_TYPE_MASK)
+
+#define JA_ENTRY_PER_NODE	256UL
+
+/*
+ * Entry for NULL node is at index 8 of the table. It is never encoded
+ * in flags.
+ */
+#define NODE_INDEX_NULL		8
+
+/*
+ * Iteration on the array to find the right node size for the number of
+ * children stops when it reaches .max_child == 256 (this is the largest
+ * possible node size, which contains 256 children).
+ * The min_child overlaps with the previous max_child to provide an
+ * hysteresis loop to reallocation for patterns of cyclic add/removal
+ * within the same node.
+ * The node the index within the following arrays is represented on 3
+ * bits. It identifies the node type, min/max number of children, and
+ * the size order.
+ * The max_child values for the RCU_JA_POOL below result from
+ * statistical approximation: over million populations, the max_child
+ * covers between 97% and 99% of the populations generated. Therefore, a
+ * fallback should exist to cover the rare extreme population unbalance
+ * cases, but it will not have a major impact on speed nor space
+ * consumption, since those are rare cases.
+ */
+
+#if (CAA_BITS_PER_LONG < 64)
+/* 32-bit pointers */
+enum {
+	ja_type_0_max_child = 1,
+	ja_type_1_max_child = 3,
+	ja_type_2_max_child = 6,
+	ja_type_3_max_child = 12,
+	ja_type_4_max_child = 25,
+	ja_type_5_max_child = 48,
+	ja_type_6_max_child = 92,
+	ja_type_7_max_child = 256,
+	ja_type_8_max_child = 0,	/* NULL */
+};
+
+enum {
+	ja_type_0_max_linear_child = 1,
+	ja_type_1_max_linear_child = 3,
+	ja_type_2_max_linear_child = 6,
+	ja_type_3_max_linear_child = 12,
+	ja_type_4_max_linear_child = 25,
+	ja_type_5_max_linear_child = 24,
+	ja_type_6_max_linear_child = 23,
+};
+
+enum {
+	ja_type_5_nr_pool_order = 1,
+	ja_type_6_nr_pool_order = 2,
+};
+
+const struct rcu_ja_type ja_types[] = {
+	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_0_max_child, .max_linear_child = ja_type_0_max_linear_child, .order = 3, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_1_max_child, .max_linear_child = ja_type_1_max_linear_child, .order = 4, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 3, .max_child = ja_type_2_max_child, .max_linear_child = ja_type_2_max_linear_child, .order = 5, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 4, .max_child = ja_type_3_max_child, .max_linear_child = ja_type_3_max_linear_child, .order = 6, },
+	{ .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 */
+	{ .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, },
+	{ .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.
+	 */
+	{ .type_class = RCU_JA_PIGEON, .min_child = 89, .max_child = ja_type_7_max_child, .order = 10, },
+
+	{ .type_class = RCU_JA_NULL, .min_child = 0, .max_child = ja_type_8_max_child, },
+};
+#else /* !(CAA_BITS_PER_LONG < 64) */
+/* 64-bit pointers */
+enum {
+	ja_type_0_max_child = 1,
+	ja_type_1_max_child = 3,
+	ja_type_2_max_child = 7,
+	ja_type_3_max_child = 14,
+	ja_type_4_max_child = 28,
+	ja_type_5_max_child = 54,
+	ja_type_6_max_child = 104,
+	ja_type_7_max_child = 256,
+	ja_type_8_max_child = 256,
+};
+
+enum {
+	ja_type_0_max_linear_child = 1,
+	ja_type_1_max_linear_child = 3,
+	ja_type_2_max_linear_child = 7,
+	ja_type_3_max_linear_child = 14,
+	ja_type_4_max_linear_child = 28,
+	ja_type_5_max_linear_child = 27,
+	ja_type_6_max_linear_child = 26,
+};
+
+enum {
+	ja_type_5_nr_pool_order = 1,
+	ja_type_6_nr_pool_order = 2,
+};
+
+const struct rcu_ja_type ja_types[] = {
+	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_0_max_child, .max_linear_child = ja_type_0_max_linear_child, .order = 4, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 1, .max_child = ja_type_1_max_child, .max_linear_child = ja_type_1_max_linear_child, .order = 5, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 3, .max_child = ja_type_2_max_child, .max_linear_child = ja_type_2_max_linear_child, .order = 6, },
+	{ .type_class = RCU_JA_LINEAR, .min_child = 5, .max_child = ja_type_3_max_child, .max_linear_child = ja_type_3_max_linear_child, .order = 7, },
+	{ .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. */
+	{ .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, },
+	{ .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.
+	 */
+	{ .type_class = RCU_JA_PIGEON, .min_child = 101, .max_child = ja_type_7_max_child, .order = 11, },
+
+	{ .type_class = RCU_JA_NULL, .min_child = 0, .max_child = ja_type_8_max_child, },
+};
+#endif /* !(BITS_PER_LONG < 64) */
+
+static inline __attribute__((unused))
+void static_array_size_check(void)
+{
+	CAA_BUILD_BUG_ON(CAA_ARRAY_SIZE(ja_types) < JA_TYPE_MAX_NR);
+}
+
+/*
+ * The rcu_ja_node contains the compressed node data needed for
+ * read-side. For linear and pool node configurations, it starts with a
+ * byte counting the number of children in the node.  Then, the
+ * node-specific data is placed.
+ * The node mutex, if any is needed, protecting concurrent updated of
+ * each node is placed in a separate hash table indexed by node address.
+ * For the pigeon configuration, the number of children is also kept in
+ * a separate hash table, indexed by node address, because it is only
+ * required for updates.
+ */
+
+#define DECLARE_LINEAR_NODE(index)								\
+	struct {										\
+		uint8_t nr_child;								\
+		uint8_t child_value[ja_type_## index ##_max_linear_child];			\
+		struct rcu_ja_node_flag *child_ptr[ja_type_## index ##_max_linear_child];	\
+	}
+
+#define DECLARE_POOL_NODE(index)								\
+	struct {										\
+		struct {									\
+			uint8_t nr_child;							\
+			uint8_t child_value[ja_type_## index ##_max_linear_child];		\
+			struct rcu_ja_node_flag *child_ptr[ja_type_## index ##_max_linear_child]; \
+		} linear[1U << ja_type_## index ##_nr_pool_order];				\
+	}
+
+struct rcu_ja_node {
+	union {
+		/* Linear configuration */
+		DECLARE_LINEAR_NODE(0) conf_0;
+		DECLARE_LINEAR_NODE(1) conf_1;
+		DECLARE_LINEAR_NODE(2) conf_2;
+		DECLARE_LINEAR_NODE(3) conf_3;
+		DECLARE_LINEAR_NODE(4) conf_4;
+
+		/* Pool configuration */
+		DECLARE_POOL_NODE(5) conf_5;
+		DECLARE_POOL_NODE(6) conf_6;
+
+		/* Pigeon configuration */
+		struct {
+			struct rcu_ja_node_flag *child[ja_type_7_max_child];
+		} conf_7;
+		/* data aliasing nodes for computed accesses */
+		uint8_t data[sizeof(struct rcu_ja_node_flag *) * ja_type_7_max_child];
+	} u;
+};
+
+static
+struct rcu_ja_node_flag *ja_node_flag(struct rcu_ja_node *node,
+		unsigned int type)
+{
+	assert(type < RCU_JA_NR_TYPES);
+	return (struct rcu_ja_node_flag *) (((unsigned long) node) | type);
+}
+
+static
+struct rcu_ja_node *ja_node_ptr(struct rcu_ja_node_flag *node)
+{
+	return (struct rcu_ja_node *) (((unsigned long) node) | JA_PTR_MASK);
+}
+
+static
+unsigned int ja_node_type(struct rcu_ja_node_flag *node)
+{
+	unsigned int type;
+
+	if (ja_node_ptr(node) == NULL) {
+		return NODE_INDEX_NULL;
+	}
+	type = (unsigned int) ((unsigned long) node & JA_TYPE_MASK);
+	assert(type < RCU_JA_NR_TYPES);
+	return type;
+}
+
+struct rcu_ja_node *alloc_rcu_ja_node(const struct rcu_ja_type *ja_type)
+{
+	return calloc(1U << ja_type->order, sizeof(char));
+}
+
+void free_rcu_ja_node(struct rcu_ja_node *node)
+{
+	free(node);
+}
+
+#define __JA_ALIGN_MASK(v, mask)	(((v) + (mask)) & ~(mask))
+#define JA_ALIGN(v, align)		__JA_ALIGN_MASK(v, (typeof(v)) (align) - 1)
+#define __JA_FLOOR_MASK(v, mask)	((v) & ~(mask))
+#define JA_FLOOR(v, align)		__JA_FLOOR_MASK(v, (typeof(v)) (align) - 1)
+
+static
+uint8_t *align_ptr_size(uint8_t *ptr)
+{
+	return (uint8_t *) JA_ALIGN((unsigned long) ptr, sizeof(void *));
+}
+
+static
+uint8_t ja_linear_node_get_nr_child(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node)
+{
+	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
+	return CMM_LOAD_SHARED(node->u.data[0]);
+}
+
+/*
+ * The order in which values and pointers are does does not matter: if
+ * a value is missing, we return NULL. If a value is there, but its
+ * associated pointers is still NULL, we return NULL too.
+ */
+static
+struct rcu_ja_node_flag *ja_linear_node_get_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		uint8_t n)
+{
+	uint8_t nr_child;
+	uint8_t *values;
+	struct rcu_ja_node_flag **pointers;
+	struct rcu_ja_node_flag *ptr;
+	unsigned int i;
+
+	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
+
+	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];
+	for (i = 0; i < nr_child; i++) {
+		if (CMM_LOAD_SHARED(values[i]) == n)
+			break;
+	}
+	if (i >= nr_child)
+		return NULL;
+	pointers = (struct rcu_ja_node_flag **) align_ptr_size(&values[type->max_linear_child]);
+	ptr = rcu_dereference(pointers[i]);
+	assert(ja_node_ptr(ptr) != NULL);
+	return ptr;
+}
+
+static
+struct rcu_ja_node_flag *ja_linear_node_get_ith_pos(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		uint8_t i,
+		uint8_t *v,
+		struct rcu_ja_node_flag **iter)
+{
+	uint8_t *values;
+	struct rcu_ja_node_flag **pointers;
+
+	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
+	assert(i < ja_linear_node_get_nr_child(type, node));
+
+	values = &node->u.data[1];
+	*v = values[i];
+	pointers = (struct rcu_ja_node_flag **) align_ptr_size(&values[type->max_linear_child]);
+	*iter = pointers[i];
+}
+
+static
+struct rcu_ja_node_flag *ja_pool_node_get_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		uint8_t n)
+{
+	struct rcu_ja_node *linear;
+
+	assert(type->type_class == RCU_JA_POOL);
+	/*
+	 * TODO: currently, we select the pool by highest bits. We
+	 * should support various encodings.
+	 */
+	linear = (struct rcu_ja_node *)
+		&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
+	return ja_linear_node_get_nth(type, linear, n);
+}
+
+static
+struct rcu_ja_node *ja_pool_node_get_ith_pool(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		uint8_t i)
+{
+	assert(type->type_class == RCU_JA_POOL);
+	return (struct rcu_ja_node *)
+		&node->u.data[(unsigned int) i << type->pool_size_order];
+}
+
+static
+struct rcu_ja_node_flag *ja_pigeon_node_get_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		uint8_t n)
+{
+	assert(type->type_class == RCU_JA_PIGEON);
+	return rcu_dereference(((struct rcu_ja_node_flag **) node->u.data)[n]);
+}
+
+/*
+ * ja_node_get_nth: get nth item from a node.
+ * node_flag is already rcu_dereference'd.
+ */
+static
+struct rcu_ja_node_flag *ja_node_get_nth(struct rcu_ja_node_flag *node_flag,
+		uint8_t n)
+{
+	unsigned int type_index;
+	struct rcu_ja_node *node;
+	const struct rcu_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_nth(type, node, n);
+	case RCU_JA_POOL:
+		return ja_pool_node_get_nth(type, node, n);
+	case RCU_JA_PIGEON:
+		return ja_pigeon_node_get_nth(type, node, n);
+	default:
+		assert(0);
+		return (void *) -1UL;
+	}
+}
+
+/*
+ * TODO: use ja_get_nr_child to monitor limits triggering shrink
+ * recompaction.
+ * Also use ja_get_nr_child to make the difference between resize and
+ * pool change of compaction bit(s).
+ */
+static
+unsigned int ja_get_nr_child(struct rcu_ja_shadow_node *shadow_node)
+{
+	return shadow_node->nr_child;
+}
+
+static
+int ja_linear_node_set_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		struct rcu_ja_shadow_node *shadow_node,
+		uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	uint8_t nr_child;
+	uint8_t *values, *nr_child_ptr;
+	struct rcu_ja_node_flag **pointers;
+	unsigned int i;
+
+	assert(type->type_class == RCU_JA_LINEAR || type->type_class == RCU_JA_POOL);
+
+	nr_child_ptr = &node->u.data[0];
+	nr_child = *nr_child_ptr;
+	assert(nr_child <= type->max_linear_child);
+	assert(type->type_class != RCU_JA_LINEAR || nr_child >= type->min_child);
+
+	values = &node->u.data[1];
+	for (i = 0; i < nr_child; i++) {
+		if (values[i] == n)
+			return -EEXIST;
+	}
+	if (nr_child >= type->max_linear_child) {
+		/* No space left in this node type */
+		return -ENOSPC;
+	}
+	pointers = (struct rcu_ja_node_flag **) align_ptr_size(&values[type->max_linear_child]);
+	assert(pointers[nr_child] == NULL);
+	rcu_assign_pointer(pointers[nr_child], child_node_flag);
+	CMM_STORE_SHARED(values[nr_child], n);
+	cmm_smp_wmb();	/* write value and pointer before nr_child */
+	CMM_STORE_SHARED(*nr_child_ptr, nr_child + 1);
+	shadow_node->nr_child++;
+	return 0;
+}
+
+static
+int ja_pool_node_set_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		struct rcu_ja_shadow_node *shadow_node,
+		uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	struct rcu_ja_node *linear;
+
+	assert(type->type_class == RCU_JA_POOL);
+	linear = (struct rcu_ja_node *)
+		&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
+	return ja_linear_node_set_nth(type, linear, shadow_node,
+			n, child_node_flag);
+}
+
+static
+int ja_pigeon_node_set_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		struct rcu_ja_shadow_node *shadow_node,
+		uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	struct rcu_ja_node_flag **ptr;
+
+	assert(type->type_class == RCU_JA_PIGEON);
+	ptr = &((struct rcu_ja_node_flag **) node->u.data)[n];
+	if (*ptr != NULL)
+		return -EEXIST;
+	rcu_assign_pointer(*ptr, child_node_flag);
+	shadow_node->nr_child++;
+	return 0;
+}
+
+/*
+ * _ja_node_set_nth: set nth item within a node. Return an error
+ * (negative error value) if it is already there.
+ * TODO: exclusive access on node.
+ */
+static
+int _ja_node_set_nth(const struct rcu_ja_type *type,
+		struct rcu_ja_node *node,
+		struct rcu_ja_shadow_node *shadow_node,
+		uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	switch (type->type_class) {
+	case RCU_JA_LINEAR:
+		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,
+				child_node_flag);
+	case RCU_JA_PIGEON:
+		return ja_pigeon_node_set_nth(type, node, shadow_node, n,
+				child_node_flag);
+	case RCU_JA_NULL:
+		return -ENOSPC;
+	default:
+		assert(0);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * ja_node_recompact_add: recompact a node, adding a new child.
+ * TODO: for pool type, take selection bit(s) into account.
+ */
+static
+int ja_node_recompact_add(struct rcu_ja *ja,
+		unsigned int old_type_index,
+		const struct rcu_ja_type *old_type,
+		struct rcu_ja_node *old_node,
+		struct rcu_ja_shadow_node **shadow_node,
+		struct rcu_ja_node_flag **old_node_flag, uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	unsigned int new_type_index;
+	struct rcu_ja_node *new_node;
+	const struct rcu_ja_type *new_type;
+	struct rcu_ja_node_flag *new_node_flag;
+	int ret;
+
+	if (*shadow_node == NULL) {
+		new_type_index = 0;
+	} else {
+		new_type_index = old_type_index + 1;
+	}
+	new_type = &ja_types[new_type_index];
+	new_node = alloc_rcu_ja_node(new_type);
+	if (!new_node)
+		return -ENOMEM;
+	new_node_flag = ja_node_flag(new_node, new_type_index);
+
+	ret = rcuja_shadow_set(ja->ht, new_node, *shadow_node);
+	if (ret)
+		return ret;
+
+	if (*shadow_node == NULL) {
+		*shadow_node = rcuja_shadow_lookup_lock(ja->ht, new_node);
+		assert(*shadow_node);
+	}
+
+	/*
+	 * We need to clear nr_child, because it will be re-incremented
+	 * by _ja_node_set_nth().
+	 */
+	(*shadow_node)->nr_child = 0;
+
+	assert(old_type->type_class != RCU_JA_PIGEON);
+	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 rcu_ja_node_flag *iter;
+			uint8_t v;
+
+			ja_linear_node_get_ith_pos(old_type, old_node, i, &v, &iter);
+			if (!iter)
+				continue;
+			ret = _ja_node_set_nth(new_type, new_node, *shadow_node,
+					v, iter);
+			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 rcu_ja_node *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++) {
+				struct rcu_ja_node_flag *iter;
+				uint8_t v;
+
+				ja_linear_node_get_ith_pos(old_type, pool,
+						j, &v, &iter);
+				if (!iter)
+					continue;
+				ret = _ja_node_set_nth(new_type, new_node, *shadow_node,
+						v, iter);
+				assert(!ret);
+			}
+		}
+		break;
+	}
+	case RCU_JA_PIGEON:
+	default:
+		assert(0);
+		return -EINVAL;
+	}
+
+	/* add node */
+	ret = _ja_node_set_nth(new_type, new_node, *shadow_node,
+			n, child_node_flag);
+	assert(!ret);
+	/* Replace the old node with the new recompacted one */
+	rcu_assign_pointer(*old_node_flag, new_node_flag);
+	ret = rcuja_shadow_clear(ja->ht, old_node,
+			RCUJA_SHADOW_CLEAR_FREE_NODE);
+	assert(!ret);
+	return 0;
+}
+
+static
+int ja_node_set_nth(struct rcu_ja *ja,
+		struct rcu_ja_node_flag **node_flag, uint8_t n,
+		struct rcu_ja_node_flag *child_node_flag)
+{
+	int ret;
+	unsigned int type_index;
+	const struct rcu_ja_type *type;
+	struct rcu_ja_node *node;
+	struct rcu_ja_shadow_node *shadow_node = NULL;
 
+	node = ja_node_ptr(*node_flag);
+	type_index = ja_node_type(*node_flag);
+	type = &ja_types[type_index];
+	if (node != NULL) {
+		shadow_node = rcuja_shadow_lookup_lock(ja->ht, node);
+		assert(shadow_node);
+	}
+	ret = _ja_node_set_nth(type, node, shadow_node,
+			n, child_node_flag);
+	if (ret == -ENOSPC) {
+		/* Not enough space in node, need to recompact. */
+		ret = ja_node_recompact_add(ja, type_index, type, node,
+				&shadow_node, node_flag, n, child_node_flag);
+		/* recompact always leave shadow_node locked */
+	}
+	rcuja_shadow_unlock(shadow_node);
+	return ret;
+}