[userspace-rcu.git] / rcuja / rcuja.c

/*
 * rcuja/rcuja.c
 *
 * Userspace RCU library - RCU Judy Array
 *
 * Copyright 2012 - 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
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * 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,
};

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

/*
 * 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,
};

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, },
};
#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,
};

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, },
};
#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
unsigned int ja_node_type(struct rcu_ja_node_flag *node)
{
	unsigned int type;

	type = (unsigned int) ((unsigned long) node & JA_TYPE_MASK);
	assert(type < RCU_JA_NR_TYPES);
	return 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);
}

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 *));
}

/*
 * 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 = CMM_LOAD_SHARED(node->u.data[0]);
	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_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);
	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_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;
	}
}

static
int ja_linear_node_set_nth(const struct rcu_ja_type *type,
		struct rcu_ja_node *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);
	return 0;
}

static
int ja_pool_node_set_nth(const struct rcu_ja_type *type,
		struct rcu_ja_node *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, n, child_node_flag);
}

static
int ja_pigeon_node_set_nth(const struct rcu_ja_type *type,
		struct rcu_ja_node *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);
	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(struct rcu_ja_node_flag *node_flag, uint8_t n,
		struct rcu_ja_node_flag *child_node_flag)
{
	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_set_nth(type, node, n,
				child_node_flag);
	case RCU_JA_POOL:
		return ja_pool_node_set_nth(type, node, n,
				child_node_flag);
	case RCU_JA_PIGEON:
		return ja_pigeon_node_set_nth(type, node, n,
				child_node_flag);
	default:
		assert(0);
		return -EINVAL;
	}

	return 0;
}

/*
 * ja_node_recompact_add: recompact a node, adding a new child.
 */
static
int ja_node_recompact_add(struct rcu_ja_node_flag **old_node_flag, uint8_t n,
		struct rcu_ja_node_flag *child_node_flag)

{
	unsigned int old_type_index, new_type_index;
	struct rcu_ja_node *old_node, *new_node;
	const struct rcu_ja_type *old_type, *new_type;
	struct rcu_ja_node_flag *new_node_flag;
	unsigned int i;
	int ret;

	old_node = ja_node_ptr(*old_node_flag);
	if (old_node == NULL) {
		new_type_index = 0;
	} else {
		old_type_index = ja_node_type(*old_node_flag);
		old_type = &ja_types[old_type_index];
		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);

	for (i = 0; i < old_type->max_child; i++) {
		struct rcu_ja_node_flag *iter;

		iter = ja_node_get_nth(*old_node_flag, i);
		if (!iter)
			continue;
		ret = _ja_node_set_nth(new_node_flag, i, iter);
		assert(!ret);
	}
	/* add node */
	ret = _ja_node_set_nth(new_node_flag, n, child_node_flag);
	assert(!ret);
	/* Replace the old node with the new recompacted one */
	rcu_assign_pointer(*old_node_flag, new_node_flag);
	/* TODO: free old_node (call_rcu) */
	return 0;
}

static
int ja_node_set_nth(struct rcu_ja_node_flag **node_flag, uint8_t n,
		struct rcu_ja_node_flag *child_node_flag)
{
	int ret;

	ret = _ja_node_set_nth(*node_flag, n, child_node_flag);
	if (ret == -ENOSPC) {
		/* Not enough space in node, need to recompact */
		ret = ja_node_recompact_add(node_flag, n,
				child_node_flag);
		if (ret < 0)
			return ret;
	}
	return ret;
}
Commit	Line	Data
61009379 MD	1	/*
	2	* rcuja/rcuja.c
	3	*
	4	* Userspace RCU library - RCU Judy Array
	5	*
	6	* Copyright 2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	7	*
	8	* This library is free software; you can redistribute it and/or
	9	* modify it under the terms of the GNU Lesser General Public
	10	* License as published by the Free Software Foundation; either
	11	* version 2.1 of the License, or (at your option) any later version.
	12	*
	13	* This library is distributed in the hope that it will be useful,
	14	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	16	* Lesser General Public License for more details.
	17	*
	18	* You should have received a copy of the GNU Lesser General Public
	19	* License along with this library; if not, write to the Free Software
	20	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	21	*/
	22
195e72d3	23	#define _LGPL_SOURCE
e5227865	24	#include <stdint.h>
8e519e3c	25	#include <errno.h>
d68c6810	26	#include <limits.h>
61009379	27	#include <urcu/rcuja.h>
d68c6810 MD	28	#include <urcu/compiler.h>
	29	#include <urcu/arch.h>
	30	#include <assert.h>
8e519e3c MD	31	#include <urcu-pointer.h>
8e519e3c MD	32
61009379	33	#include "rcuja-internal.h"
d68c6810	34	#include "bitfield.h"
61009379	35
d68c6810	36	enum rcu_ja_type_class {
e5227865	37	RCU_JA_LINEAR = 0, /* Type A */
fd800776 MD	38	/* 32-bit: 1 to 25 children, 8 to 128 bytes */
	39	/* 64-bit: 1 to 28 children, 16 to 256 bytes */
	40	RCU_JA_POOL = 1, /* Type B */
	41	/* 32-bit: 26 to 100 children, 256 to 512 bytes */
	42	/* 64-bit: 29 to 112 children, 512 to 1024 bytes */
e5227865	43	RCU_JA_PIGEON = 2, /* Type C */
fd800776 MD	44	/* 32-bit: 101 to 256 children, 1024 bytes */
fd800776 MD	45	/* 64-bit: 113 to 256 children, 2048 bytes */
e5227865	46	/* Leaf nodes are implicit from their height in the tree */
1db4943c	47	RCU_JA_NR_TYPES,
e5227865 MD	48	};
e5227865 MD	49
d68c6810 MD	50	struct rcu_ja_type {
d68c6810 MD	51	enum rcu_ja_type_class type_class;
8e519e3c MD	52	uint16_t min_child; /* minimum number of children: 1 to 256 */
	53	uint16_t max_child; /* maximum number of children: 1 to 256 */
	54	uint16_t max_linear_child; /* per-pool max nr. children: 1 to 256 */
	55	uint16_t order; /* node size is (1 << order), in bytes */
fd800776 MD	56	uint16_t nr_pool_order; /* number of pools */
fd800776 MD	57	uint16_t pool_size_order; /* pool size */
e5227865 MD	58	};
e5227865 MD	59
d68c6810 MD	60	/*
	61	* Number of least significant pointer bits reserved to represent the
	62	* child type.
	63	*/
	64	#define JA_TYPE_BITS 3
	65	#define JA_TYPE_MAX_NR (1U << JA_TYPE_BITS)
	66	#define JA_TYPE_MASK (JA_TYPE_MAX_NR - 1)
	67	#define JA_PTR_MASK (~JA_TYPE_MASK)
	68
	69	#define JA_ENTRY_PER_NODE 256UL
	70
e5227865 MD	71	/*
e5227865 MD	72	* Iteration on the array to find the right node size for the number of
d68c6810	73	* children stops when it reaches .max_child == 256 (this is the largest
e5227865	74	* possible node size, which contains 256 children).
d68c6810 MD	75	* The min_child overlaps with the previous max_child to provide an
	76	* hysteresis loop to reallocation for patterns of cyclic add/removal
	77	* within the same node.
	78	* The node the index within the following arrays is represented on 3
	79	* bits. It identifies the node type, min/max number of children, and
	80	* the size order.
3d45251f MD	81	* The max_child values for the RCU_JA_POOL below result from
	82	* statistical approximation: over million populations, the max_child
	83	* covers between 97% and 99% of the populations generated. Therefore, a
	84	* fallback should exist to cover the rare extreme population unbalance
	85	* cases, but it will not have a major impact on speed nor space
	86	* consumption, since those are rare cases.
e5227865	87	*/
e5227865	88
d68c6810 MD	89	#if (CAA_BITS_PER_LONG < 64)
d68c6810 MD	90	/* 32-bit pointers */
1db4943c MD	91	enum {
	92	ja_type_0_max_child = 1,
	93	ja_type_1_max_child = 3,
	94	ja_type_2_max_child = 6,
	95	ja_type_3_max_child = 12,
	96	ja_type_4_max_child = 25,
	97	ja_type_5_max_child = 48,
	98	ja_type_6_max_child = 92,
	99	ja_type_7_max_child = 256,
	100	};
	101
8e519e3c MD	102	enum {
	103	ja_type_0_max_linear_child = 1,
	104	ja_type_1_max_linear_child = 3,
	105	ja_type_2_max_linear_child = 6,
	106	ja_type_3_max_linear_child = 12,
	107	ja_type_4_max_linear_child = 25,
	108	ja_type_5_max_linear_child = 24,
	109	ja_type_6_max_linear_child = 23,
	110	};
	111
1db4943c MD	112	enum {
	113	ja_type_5_nr_pool_order = 1,
	114	ja_type_6_nr_pool_order = 2,
	115	};
	116
d68c6810	117	const struct rcu_ja_type ja_types[] = {
8e519e3c MD	118	{ .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, },
	119	{ .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, },
	120	{ .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, },
	121	{ .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, },
	122	{ .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, },
e5227865	123
fd800776	124	/* Pools may fill sooner than max_child */
8e519e3c MD	125	{ .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, },
8e519e3c MD	126	{ .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, },
3d45251f MD	127
	128	/*
	129	* TODO: Upon node removal below min_child, if child pool is
	130	* filled beyond capacity, we need to roll back to pigeon.
	131	*/
1db4943c	132	{ .type_class = RCU_JA_PIGEON, .min_child = 89, .max_child = ja_type_7_max_child, .order = 10, },
d68c6810	133	};
d68c6810 MD	134	#else /* !(CAA_BITS_PER_LONG < 64) */
d68c6810 MD	135	/* 64-bit pointers */
1db4943c MD	136	enum {
	137	ja_type_0_max_child = 1,
	138	ja_type_1_max_child = 3,
	139	ja_type_2_max_child = 7,
	140	ja_type_3_max_child = 14,
	141	ja_type_4_max_child = 28,
	142	ja_type_5_max_child = 54,
	143	ja_type_6_max_child = 104,
	144	ja_type_7_max_child = 256,
	145	};
	146
8e519e3c MD	147	enum {
	148	ja_type_0_max_linear_child = 1,
	149	ja_type_1_max_linear_child = 3,
	150	ja_type_2_max_linear_child = 7,
	151	ja_type_3_max_linear_child = 14,
	152	ja_type_4_max_linear_child = 28,
	153	ja_type_5_max_linear_child = 27,
	154	ja_type_6_max_linear_child = 26,
	155	};
	156
1db4943c MD	157	enum {
	158	ja_type_5_nr_pool_order = 1,
	159	ja_type_6_nr_pool_order = 2,
	160	};
	161
d68c6810	162	const struct rcu_ja_type ja_types[] = {
8e519e3c MD	163	{ .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, },
	164	{ .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, },
	165	{ .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, },
	166	{ .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, },
	167	{ .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, },
e5227865	168
3d45251f	169	/* Pools may fill sooner than max_child. */
8e519e3c MD	170	{ .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, },
8e519e3c MD	171	{ .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, },
e5227865	172
3d45251f MD	173	/*
	174	* TODO: Upon node removal below min_child, if child pool is
	175	* filled beyond capacity, we need to roll back to pigeon.
	176	*/
1db4943c	177	{ .type_class = RCU_JA_PIGEON, .min_child = 101, .max_child = ja_type_7_max_child, .order = 11, },
e5227865	178	};
d68c6810	179	#endif /* !(BITS_PER_LONG < 64) */
e5227865	180
1db4943c MD	181	static inline __attribute__((unused))
	182	void static_array_size_check(void)
	183	{
	184	CAA_BUILD_BUG_ON(CAA_ARRAY_SIZE(ja_types) > JA_TYPE_MAX_NR);
	185	}
	186
e5227865	187	/*
1db4943c MD	188	* The rcu_ja_node contains the compressed node data needed for
	189	* read-side. For linear and pool node configurations, it starts with a
	190	* byte counting the number of children in the node. Then, the
	191	* node-specific data is placed.
	192	* The node mutex, if any is needed, protecting concurrent updated of
	193	* each node is placed in a separate hash table indexed by node address.
	194	* For the pigeon configuration, the number of children is also kept in
	195	* a separate hash table, indexed by node address, because it is only
	196	* required for updates.
e5227865	197	*/
1db4943c	198
ff38c745 MD	199	#define DECLARE_LINEAR_NODE(index) \
	200	struct { \
	201	uint8_t nr_child; \
	202	uint8_t child_value[ja_type_## index ##_max_linear_child]; \
	203	struct rcu_ja_node_flag *child_ptr[ja_type_## index ##_max_linear_child]; \
	204	}
	205
	206	#define DECLARE_POOL_NODE(index) \
	207	struct { \
	208	struct { \
	209	uint8_t nr_child; \
	210	uint8_t child_value[ja_type_## index ##_max_linear_child]; \
	211	struct rcu_ja_node_flag *child_ptr[ja_type_## index ##_max_linear_child]; \
	212	} linear[1U << ja_type_## index ##_nr_pool_order]; \
	213	}
1db4943c	214
e5227865	215	struct rcu_ja_node {
1db4943c MD	216	union {
	217	/* Linear configuration */
	218	DECLARE_LINEAR_NODE(0) conf_0;
	219	DECLARE_LINEAR_NODE(1) conf_1;
	220	DECLARE_LINEAR_NODE(2) conf_2;
	221	DECLARE_LINEAR_NODE(3) conf_3;
	222	DECLARE_LINEAR_NODE(4) conf_4;
	223
	224	/* Pool configuration */
	225	DECLARE_POOL_NODE(5) conf_5;
	226	DECLARE_POOL_NODE(6) conf_6;
	227
	228	/* Pigeon configuration */
	229	struct {
	230	struct rcu_ja_node_flag *child[ja_type_7_max_child];
	231	} conf_7;
	232	/* data aliasing nodes for computed accesses */
	233	uint8_t data[sizeof(struct rcu_ja_node_flag ) ja_type_7_max_child];
	234	} u;
e5227865 MD	235	};
e5227865 MD	236
d68c6810	237	static
8e519e3c MD	238	struct rcu_ja_node_flag ja_node_flag(struct rcu_ja_node node,
8e519e3c MD	239	unsigned int type)
d68c6810	240	{
1db4943c	241	assert(type < RCU_JA_NR_TYPES);
d68c6810 MD	242	return (struct rcu_ja_node_flag *) (((unsigned long) node) \| type);
	243	}
	244
	245	static
	246	unsigned int ja_node_type(struct rcu_ja_node_flag *node)
	247	{
	248	unsigned int type;
	249
	250	type = (unsigned int) ((unsigned long) node & JA_TYPE_MASK);
1db4943c	251	assert(type < RCU_JA_NR_TYPES);
d68c6810 MD	252	return type;
	253	}
	254
	255	static
	256	struct rcu_ja_node ja_node_ptr(struct rcu_ja_node_flag node)
	257	{
	258	return (struct rcu_ja_node *) (((unsigned long) node) \| JA_PTR_MASK);
	259	}
	260
7a0b2331	261	struct rcu_ja_node alloc_rcu_ja_node(const struct rcu_ja_type ja_type)
e5227865	262	{
1db4943c	263	return calloc(1U << ja_type->order, sizeof(char));
e5227865 MD	264	}
	265
	266	void free_rcu_ja_node(struct rcu_ja_node *node)
	267	{
	268	free(node);
	269	}
	270
d68c6810 MD	271	#define __JA_ALIGN_MASK(v, mask) (((v) + (mask)) & ~(mask))
	272	#define JA_ALIGN(v, align) __JA_ALIGN_MASK(v, (typeof(v)) (align) - 1)
	273	#define __JA_FLOOR_MASK(v, mask) ((v) & ~(mask))
	274	#define JA_FLOOR(v, align) __JA_FLOOR_MASK(v, (typeof(v)) (align) - 1)
	275
	276	static
1db4943c	277	uint8_t align_ptr_size(uint8_t ptr)
d68c6810	278	{
1db4943c	279	return (uint8_t ) JA_ALIGN((unsigned long) ptr, sizeof(void ));
d68c6810 MD	280	}
d68c6810 MD	281
13a7f5a6 MD	282	/*
	283	* The order in which values and pointers are does does not matter: if
	284	* a value is missing, we return NULL. If a value is there, but its
	285	* associated pointers is still NULL, we return NULL too.
	286	*/
d68c6810 MD	287	static
d68c6810 MD	288	struct rcu_ja_node_flag ja_linear_node_get_nth(const struct rcu_ja_type type,
8e519e3c MD	289	struct rcu_ja_node *node,
8e519e3c MD	290	uint8_t n)
d68c6810 MD	291	{
	292	uint8_t nr_child;
	293	uint8_t *values;
1db4943c	294	struct rcu_ja_node_flag **pointers;
d68c6810 MD	295	struct rcu_ja_node_flag *ptr;
	296	unsigned int i;
	297
8e519e3c	298	assert(type->type_class == RCU_JA_LINEAR \|\| type->type_class == RCU_JA_POOL);
d68c6810	299
13a7f5a6 MD	300	nr_child = CMM_LOAD_SHARED(node->u.data[0]);
13a7f5a6 MD	301	cmm_smp_rmb(); /* read nr_child before values and pointers */
8e519e3c MD	302	assert(nr_child <= type->max_linear_child);
8e519e3c MD	303	assert(type->type_class != RCU_JA_LINEAR \|\| nr_child >= type->min_child);
d68c6810	304
1db4943c	305	values = &node->u.data[1];
d68c6810	306	for (i = 0; i < nr_child; i++) {
13a7f5a6	307	if (CMM_LOAD_SHARED(values[i]) == n)
d68c6810 MD	308	break;
	309	}
	310	if (i >= nr_child)
	311	return NULL;
8e519e3c	312	pointers = (struct rcu_ja_node_flag **) align_ptr_size(&values[type->max_linear_child]);
13a7f5a6	313	ptr = rcu_dereference(pointers[i]);
d68c6810 MD	314	assert(ja_node_ptr(ptr) != NULL);
	315	return ptr;
	316	}
	317
d68c6810	318	static
fd800776	319	struct rcu_ja_node_flag ja_pool_node_get_nth(const struct rcu_ja_type type,
8e519e3c MD	320	struct rcu_ja_node *node,
8e519e3c MD	321	uint8_t n)
d68c6810	322	{
fd800776	323	struct rcu_ja_node *linear;
d68c6810	324
fd800776 MD	325	assert(type->type_class == RCU_JA_POOL);
fd800776 MD	326	linear = (struct rcu_ja_node *)
1db4943c	327	&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
8e519e3c	328	return ja_linear_node_get_nth(type, linear, n);
d68c6810 MD	329	}
	330
	331	static
	332	struct rcu_ja_node_flag ja_pigeon_node_get_nth(const struct rcu_ja_type type,
8e519e3c MD	333	struct rcu_ja_node *node,
8e519e3c MD	334	uint8_t n)
d68c6810 MD	335	{
d68c6810 MD	336	assert(type->type_class == RCU_JA_PIGEON);
13a7f5a6	337	return rcu_dereference(((struct rcu_ja_node_flag **) node->u.data)[n]);
d68c6810 MD	338	}
d68c6810 MD	339
13a7f5a6 MD	340	/*
	341	* ja_node_get_nth: get nth item from a node.
	342	* node_flag is already rcu_dereference'd.
	343	*/
d68c6810 MD	344	static
d68c6810 MD	345	struct rcu_ja_node_flag ja_node_get_nth(struct rcu_ja_node_flag node_flag,
8e519e3c	346	uint8_t n)
d68c6810 MD	347	{
	348	unsigned int type_index;
	349	struct rcu_ja_node *node;
	350	const struct rcu_ja_type *type;
	351
d68c6810 MD	352	node = ja_node_ptr(node_flag);
	353	assert(node != NULL);
	354	type_index = ja_node_type(node_flag);
	355	type = &ja_types[type_index];
	356
	357	switch (type->type_class) {
	358	case RCU_JA_LINEAR:
	359	return ja_linear_node_get_nth(type, node, n);
fd800776 MD	360	case RCU_JA_POOL:
fd800776 MD	361	return ja_pool_node_get_nth(type, node, n);
d68c6810 MD	362	case RCU_JA_PIGEON:
	363	return ja_pigeon_node_get_nth(type, node, n);
	364	default:
	365	assert(0);
	366	return (void *) -1UL;
	367	}
	368	}
	369
8e519e3c MD	370	static
	371	int ja_linear_node_set_nth(const struct rcu_ja_type *type,
	372	struct rcu_ja_node *node,
	373	uint8_t n,
	374	struct rcu_ja_node_flag *child_node_flag)
	375	{
	376	uint8_t nr_child;
	377	uint8_t values, nr_child_ptr;
	378	struct rcu_ja_node_flag **pointers;
	379	unsigned int i;
	380
	381	assert(type->type_class == RCU_JA_LINEAR \|\| type->type_class == RCU_JA_POOL);
	382
	383	nr_child_ptr = &node->u.data[0];
	384	nr_child = *nr_child_ptr;
	385	assert(nr_child <= type->max_linear_child);
	386	assert(type->type_class != RCU_JA_LINEAR \|\| nr_child >= type->min_child);
	387
	388	values = &node->u.data[1];
	389	for (i = 0; i < nr_child; i++) {
	390	if (values[i] == n)
	391	return -EEXIST;
	392	}
	393	if (nr_child >= type->max_linear_child) {
	394	/* No space left in this node type */
	395	return -ENOSPC;
	396	}
	397	pointers = (struct rcu_ja_node_flag **) align_ptr_size(&values[type->max_linear_child]);
13a7f5a6 MD	398	assert(pointers[nr_child] == NULL);
	399	rcu_assign_pointer(pointers[nr_child], child_node_flag);
	400	CMM_STORE_SHARED(values[nr_child], n);
	401	cmm_smp_wmb(); /* write value and pointer before nr_child */
	402	CMM_STORE_SHARED(*nr_child_ptr, nr_child + 1);
8e519e3c MD	403	return 0;
	404	}
	405
	406	static
	407	int ja_pool_node_set_nth(const struct rcu_ja_type *type,
	408	struct rcu_ja_node *node,
	409	uint8_t n,
	410	struct rcu_ja_node_flag *child_node_flag)
	411	{
	412	struct rcu_ja_node *linear;
	413
	414	assert(type->type_class == RCU_JA_POOL);
	415	linear = (struct rcu_ja_node *)
	416	&node->u.data[((unsigned long) n >> (CHAR_BIT - type->nr_pool_order)) << type->pool_size_order];
	417	return ja_linear_node_set_nth(type, linear, n, child_node_flag);
	418	}
	419
	420	static
	421	int ja_pigeon_node_set_nth(const struct rcu_ja_type *type,
	422	struct rcu_ja_node *node,
	423	uint8_t n,
	424	struct rcu_ja_node_flag *child_node_flag)
	425	{
	426	struct rcu_ja_node_flag **ptr;
	427
	428	assert(type->type_class == RCU_JA_PIGEON);
	429	ptr = &((struct rcu_ja_node_flag **) node->u.data)[n];
	430	if (*ptr != NULL)
	431	return -EEXIST;
	432	rcu_assign_pointer(*ptr, child_node_flag);
	433	return 0;
	434	}
	435
d68c6810	436	/*
7a0b2331	437	* _ja_node_set_nth: set nth item within a node. Return an error
8e519e3c MD	438	* (negative error value) if it is already there.
8e519e3c MD	439	* TODO: exclusive access on node.
d68c6810	440	*/
8e519e3c	441	static
7a0b2331	442	int _ja_node_set_nth(struct rcu_ja_node_flag *node_flag, uint8_t n,
8e519e3c MD	443	struct rcu_ja_node_flag *child_node_flag)
	444	{
	445	unsigned int type_index;
	446	struct rcu_ja_node *node;
	447	const struct rcu_ja_type *type;
e5227865	448
8e519e3c MD	449	node = ja_node_ptr(node_flag);
	450	assert(node != NULL);
	451	type_index = ja_node_type(node_flag);
	452	type = &ja_types[type_index];
	453
	454	switch (type->type_class) {
	455	case RCU_JA_LINEAR:
	456	return ja_linear_node_set_nth(type, node, n,
	457	child_node_flag);
	458	case RCU_JA_POOL:
	459	return ja_pool_node_set_nth(type, node, n,
	460	child_node_flag);
	461	case RCU_JA_PIGEON:
	462	return ja_pigeon_node_set_nth(type, node, n,
	463	child_node_flag);
	464	default:
	465	assert(0);
	466	return -EINVAL;
	467	}
	468
	469	return 0;
	470	}
7a0b2331 MD	471
	472	/*
	473	* ja_node_recompact_add: recompact a node, adding a new child.
	474	*/
	475	static
	476	int ja_node_recompact_add(struct rcu_ja_node_flag **old_node_flag, uint8_t n,
	477	struct rcu_ja_node_flag *child_node_flag)
	478
	479	{
	480	unsigned int old_type_index, new_type_index;
	481	struct rcu_ja_node old_node, new_node;
	482	const struct rcu_ja_type old_type, new_type;
	483	struct rcu_ja_node_flag *new_node_flag;
	484	unsigned int i;
	485	int ret;
	486
	487	old_node = ja_node_ptr(*old_node_flag);
	488	if (old_node == NULL) {
	489	new_type_index = 0;
	490	} else {
	491	old_type_index = ja_node_type(*old_node_flag);
	492	old_type = &ja_types[old_type_index];
	493	new_type_index = old_type_index + 1;
	494	}
	495	new_type = &ja_types[new_type_index];
	496	new_node = alloc_rcu_ja_node(new_type);
	497	if (!new_node)
	498	return -ENOMEM;
	499	new_node_flag = ja_node_flag(new_node, new_type_index);
	500
	501	for (i = 0; i < old_type->max_child; i++) {
	502	struct rcu_ja_node_flag *iter;
	503
	504	iter = ja_node_get_nth(*old_node_flag, i);
	505	if (!iter)
	506	continue;
	507	ret = _ja_node_set_nth(new_node_flag, i, iter);
	508	assert(!ret);
	509	}
	510	/* add node */
	511	ret = _ja_node_set_nth(new_node_flag, n, child_node_flag);
	512	assert(!ret);
8eba1a4b MD	513	/* Replace the old node with the new recompacted one */
	514	rcu_assign_pointer(*old_node_flag, new_node_flag);
	515	/* TODO: free old_node (call_rcu) */
7a0b2331 MD	516	return 0;
	517	}
	518
	519	static
	520	int ja_node_set_nth(struct rcu_ja_node_flag **node_flag, uint8_t n,
	521	struct rcu_ja_node_flag *child_node_flag)
	522	{
	523	int ret;
	524
	525	ret = _ja_node_set_nth(*node_flag, n, child_node_flag);
	526	if (ret == -ENOSPC) {
	527	/* Not enough space in node, need to recompact */
	528	ret = ja_node_recompact_add(node_flag, n,
	529	child_node_flag);
	530	if (ret < 0)
	531	return ret;
	532	}
	533	return ret;
	534	}