subr_pctrie.c

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/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2013 EMC Corp.
 * Copyright (c) 2011 Jeffrey Roberson <jeff@freebsd.org>
 * Copyright (c) 2008 Mayur Shardul <mayur.shardul@gmail.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */
 
/*
 * Path-compressed radix trie implementation.
 *
 * The implementation takes into account the following rationale:
 * - Size of the nodes should be as small as possible but still big enough
 *   to avoid a large maximum depth for the trie.  This is a balance
 *   between the necessity to not wire too much physical memory for the nodes
 *   and the necessity to avoid too much cache pollution during the trie
 *   operations.
 * - There is not a huge bias toward the number of lookup operations over
 *   the number of insert and remove operations.  This basically implies
 *   that optimizations supposedly helping one operation but hurting the
 *   other might be carefully evaluated.
 * - On average not many nodes are expected to be fully populated, hence
 *   level compression may just complicate things.
 */
 
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include "opt_ddb.h"
 
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/pctrie.h>
#include <sys/proc.h>   /* smr.h depends on struct thread. */
#include <sys/smr.h>
#include <sys/smr_types.h>
 
#ifdef DDB
#include <ddb/ddb.h>
#endif
 
#define PCTRIE_MASK     (PCTRIE_COUNT - 1)
#define PCTRIE_LIMIT    (howmany(sizeof(uint64_t) * NBBY, PCTRIE_WIDTH) - 1)
 
/* Flag bits stored in node pointers. */
#define PCTRIE_ISLEAF   0x1
#define PCTRIE_FLAGS    0x1
#define PCTRIE_PAD      PCTRIE_FLAGS
 
/* Returns one unit associated with specified level. */
#define PCTRIE_UNITLEVEL(lev)                                           \
        ((uint64_t)1 << ((lev) * PCTRIE_WIDTH))
 
struct pctrie_node;
typedef SMR_POINTER(struct pctrie_node *) smr_pctnode_t;
 
struct pctrie_node {
        uint64_t        pn_owner;                       /* Owner of record. */
        uint16_t        pn_count;                       /* Valid children. */
        uint8_t         pn_clev;                        /* Current level. */
        int8_t          pn_last;                        /* Zero last ptr. */
        smr_pctnode_t   pn_child[PCTRIE_COUNT];         /* Child nodes. */
};
 
enum pctrie_access { PCTRIE_SMR, PCTRIE_LOCKED, PCTRIE_UNSERIALIZED };
 
static __inline void pctrie_node_store(smr_pctnode_t *p, void *val,
    enum pctrie_access access);
 
/*
 * Allocate a node.  Pre-allocation should ensure that the request
 * will always be satisfied.
 */
static struct pctrie_node *
pctrie_node_get(struct pctrie *ptree, pctrie_alloc_t allocfn, uint64_t owner,
    uint16_t count, uint16_t clevel)
{
        struct pctrie_node *node;
 
        node = allocfn(ptree);
        if (node == NULL)
                return (NULL);
 
        /*
         * We want to clear the last child pointer after the final section
         * has exited so lookup can not return false negatives.  It is done
         * here because it will be cache-cold in the dtor callback.
         */
        if (node->pn_last != 0) {
                pctrie_node_store(&node->pn_child[node->pn_last - 1], NULL,
                    PCTRIE_UNSERIALIZED);
                node->pn_last = 0;
        }
        node->pn_owner = owner;
        node->pn_count = count;
        node->pn_clev = clevel;
        return (node);
}
 
/*
 * Free radix node.
 */
static __inline void
pctrie_node_put(struct pctrie *ptree, struct pctrie_node *node,
    pctrie_free_t freefn, int8_t last)
{
#ifdef INVARIANTS
        int slot;
 
        KASSERT(node->pn_count == 0,
            ("pctrie_node_put: node %p has %d children", node,
            node->pn_count));
        for (slot = 0; slot < PCTRIE_COUNT; slot++) {
                if (slot == last)
                        continue;
                KASSERT(smr_unserialized_load(&node->pn_child[slot], true) ==
                    NULL, ("pctrie_node_put: node %p has a child", node));
        }
#endif
        node->pn_last = last + 1;
        freefn(ptree, node);
}
 
/*
 * Return the position in the array for a given level.
 */
static __inline int
pctrie_slot(uint64_t index, uint16_t level)
{
 
        return ((index >> (level * PCTRIE_WIDTH)) & PCTRIE_MASK);
}
 
/* Trims the key after the specified level. */
static __inline uint64_t
pctrie_trimkey(uint64_t index, uint16_t level)
{
        uint64_t ret;
 
        ret = index;
        if (level > 0) {
                ret >>= level * PCTRIE_WIDTH;
                ret <<= level * PCTRIE_WIDTH;
        }
        return (ret);
}
 
/*
 * Fetch a node pointer from a slot.
 */
static __inline struct pctrie_node *
pctrie_node_load(smr_pctnode_t *p, smr_t smr, enum pctrie_access access)
{
        switch (access) {
        case PCTRIE_UNSERIALIZED:
                return (smr_unserialized_load(p, true));
        case PCTRIE_LOCKED:
                return (smr_serialized_load(p, true));
        case PCTRIE_SMR:
                return (smr_entered_load(p, smr));
        }
        __assert_unreachable();
}
 
static __inline void
pctrie_node_store(smr_pctnode_t *p, void *v, enum pctrie_access access)
{
        switch (access) {
        case PCTRIE_UNSERIALIZED:
                smr_unserialized_store(p, v, true);
                break;
        case PCTRIE_LOCKED:
                smr_serialized_store(p, v, true);
                break;
        case PCTRIE_SMR:
                panic("%s: Not supported in SMR section.", __func__);
                break;
        default:
                __assert_unreachable();
                break;
        }
}
 
/*
 * Get the root node for a tree.
 */
static __inline struct pctrie_node *
pctrie_root_load(struct pctrie *ptree, smr_t smr, enum pctrie_access access)
{
        return (pctrie_node_load((smr_pctnode_t *)&ptree->pt_root, smr, access));
}
 
/*
 * Set the root node for a tree.
 */
static __inline void
pctrie_root_store(struct pctrie *ptree, struct pctrie_node *node,
    enum pctrie_access access)
{
        pctrie_node_store((smr_pctnode_t *)&ptree->pt_root, node, access);
}
 
/*
 * Returns TRUE if the specified node is a leaf and FALSE otherwise.
 */
static __inline bool
pctrie_isleaf(struct pctrie_node *node)
{
 
        return (((uintptr_t)node & PCTRIE_ISLEAF) != 0);
}
 
/*
 * Returns the associated val extracted from node.
 */
static __inline uint64_t *
pctrie_toval(struct pctrie_node *node)
{
 
        return ((uint64_t *)((uintptr_t)node & ~PCTRIE_FLAGS));
}
 
/*
 * Adds the val as a child of the provided node.
 */
static __inline void
pctrie_addval(struct pctrie_node *node, uint64_t index, uint16_t clev,
    uint64_t *val, enum pctrie_access access)
{
        int slot;
 
        slot = pctrie_slot(index, clev);
        pctrie_node_store(&node->pn_child[slot],
            (void *)((uintptr_t)val | PCTRIE_ISLEAF), access);
}
 
/*
 * Returns the slot where two keys differ.
 * It cannot accept 2 equal keys.
 */
static __inline uint16_t
pctrie_keydiff(uint64_t index1, uint64_t index2)
{
        uint16_t clev;
 
        KASSERT(index1 != index2, ("%s: passing the same key value %jx",
            __func__, (uintmax_t)index1));
 
        index1 ^= index2;
        for (clev = PCTRIE_LIMIT;; clev--)
                if (pctrie_slot(index1, clev) != 0)
                        return (clev);
}
 
/*
 * Returns TRUE if it can be determined that key does not belong to the
 * specified node.  Otherwise, returns FALSE.
 */
static __inline bool
pctrie_keybarr(struct pctrie_node *node, uint64_t idx)
{
 
        if (node->pn_clev < PCTRIE_LIMIT) {
                idx = pctrie_trimkey(idx, node->pn_clev + 1);
                return (idx != node->pn_owner);
        }
        return (false);
}
 
/*
 * Internal helper for pctrie_reclaim_allnodes().
 * This function is recursive.
 */
static void
pctrie_reclaim_allnodes_int(struct pctrie *ptree, struct pctrie_node *node,
    pctrie_free_t freefn)
{
        struct pctrie_node *child;
        int slot;
 
        KASSERT(node->pn_count <= PCTRIE_COUNT,
            ("pctrie_reclaim_allnodes_int: bad count in node %p", node));
        for (slot = 0; node->pn_count != 0; slot++) {
                child = pctrie_node_load(&node->pn_child[slot], NULL,
                    PCTRIE_UNSERIALIZED);
                if (child == NULL)
                        continue;
                if (!pctrie_isleaf(child))
                        pctrie_reclaim_allnodes_int(ptree, child, freefn);
                pctrie_node_store(&node->pn_child[slot], NULL,
                    PCTRIE_UNSERIALIZED);
                node->pn_count--;
        }
        pctrie_node_put(ptree, node, freefn, -1);
}
 
/*
 * pctrie node zone initializer.
 */
int
pctrie_zone_init(void *mem, int size __unused, int flags __unused)
{
        struct pctrie_node *node;
 
        node = mem;
        node->pn_last = 0;
        memset(node->pn_child, 0, sizeof(node->pn_child));
        return (0);
}
 
size_t
pctrie_node_size(void)
{
 
        return (sizeof(struct pctrie_node));
}
 
/*
 * Inserts the key-value pair into the trie.
 * Panics if the key already exists.
 */
int
pctrie_insert(struct pctrie *ptree, uint64_t *val, pctrie_alloc_t allocfn)
{
        uint64_t index, newind;
        struct pctrie_node *node, *tmp;
        smr_pctnode_t *parentp;
        uint64_t *m;
        int slot;
        uint16_t clev;
 
        index = *val;
 
        /*
         * The owner of record for root is not really important because it
         * will never be used.
         */
        node = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED);
        if (node == NULL) {
                ptree->pt_root = (uintptr_t)val | PCTRIE_ISLEAF;
                return (0);
        }
        parentp = (smr_pctnode_t *)&ptree->pt_root;
        for (;;) {
                if (pctrie_isleaf(node)) {
                        m = pctrie_toval(node);
                        if (*m == index)
                                panic("%s: key %jx is already present",
                                    __func__, (uintmax_t)index);
                        clev = pctrie_keydiff(*m, index);
                        tmp = pctrie_node_get(ptree, allocfn,
                            pctrie_trimkey(index, clev + 1), 2, clev);
                        if (tmp == NULL)
                                return (ENOMEM);
                        /* These writes are not yet visible due to ordering. */
                        pctrie_addval(tmp, index, clev, val,
                            PCTRIE_UNSERIALIZED);
                        pctrie_addval(tmp, *m, clev, m, PCTRIE_UNSERIALIZED);
                        /* Synchronize to make leaf visible. */
                        pctrie_node_store(parentp, tmp, PCTRIE_LOCKED);
                        return (0);
                } else if (pctrie_keybarr(node, index))
                        break;
                slot = pctrie_slot(index, node->pn_clev);
                parentp = &node->pn_child[slot];
                tmp = pctrie_node_load(parentp, NULL, PCTRIE_LOCKED);
                if (tmp == NULL) {
                        node->pn_count++;
                        pctrie_addval(node, index, node->pn_clev, val,
                            PCTRIE_LOCKED);
                        return (0);
                }
                node = tmp;
        }
 
        /*
         * A new node is needed because the right insertion level is reached.
         * Setup the new intermediate node and add the 2 children: the
         * new object and the older edge.
         */
        newind = node->pn_owner;
        clev = pctrie_keydiff(newind, index);
        tmp = pctrie_node_get(ptree, allocfn,
            pctrie_trimkey(index, clev + 1), 2, clev);
        if (tmp == NULL)
                return (ENOMEM);
        slot = pctrie_slot(newind, clev);
        /* These writes are not yet visible due to ordering. */
        pctrie_addval(tmp, index, clev, val, PCTRIE_UNSERIALIZED);
        pctrie_node_store(&tmp->pn_child[slot], node, PCTRIE_UNSERIALIZED);
        /* Synchronize to make the above visible. */
        pctrie_node_store(parentp, tmp, PCTRIE_LOCKED);
 
        return (0);
}
 
/*
 * Returns the value stored at the index.  If the index is not present,
 * NULL is returned.
 */
static __always_inline uint64_t *
_pctrie_lookup(struct pctrie *ptree, uint64_t index, smr_t smr,
    enum pctrie_access access)
{
        struct pctrie_node *node;
        uint64_t *m;
        int slot;
 
        node = pctrie_root_load(ptree, smr, access);
        while (node != NULL) {
                if (pctrie_isleaf(node)) {
                        m = pctrie_toval(node);
                        if (*m == index)
                                return (m);
                        break;
                }
                if (pctrie_keybarr(node, index))
                        break;
                slot = pctrie_slot(index, node->pn_clev);
                node = pctrie_node_load(&node->pn_child[slot], smr, access);
        }
        return (NULL);
}
 
/*
 * Returns the value stored at the index, assuming access is externally
 * synchronized by a lock.
 *
 * If the index is not present, NULL is returned.
 */
uint64_t *
pctrie_lookup(struct pctrie *ptree, uint64_t index)
{
        return (_pctrie_lookup(ptree, index, NULL, PCTRIE_LOCKED));
}
 
/*
 * Returns the value stored at the index without requiring an external lock.
 *
 * If the index is not present, NULL is returned.
 */
uint64_t *
pctrie_lookup_unlocked(struct pctrie *ptree, uint64_t index, smr_t smr)
{
        uint64_t *res;
 
        smr_enter(smr);
        res = _pctrie_lookup(ptree, index, smr, PCTRIE_SMR);
        smr_exit(smr);
        return (res);
}
 
/*
 * Look up the nearest entry at a position bigger than or equal to index,
 * assuming access is externally synchronized by a lock.
 */
uint64_t *
pctrie_lookup_ge(struct pctrie *ptree, uint64_t index)
{
        struct pctrie_node *stack[PCTRIE_LIMIT];
        uint64_t inc;
        uint64_t *m;
        struct pctrie_node *child, *node;
#ifdef INVARIANTS
        int loops = 0;
#endif
        unsigned tos;
        int slot;
 
        node = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED);
        if (node == NULL)
                return (NULL);
        else if (pctrie_isleaf(node)) {
                m = pctrie_toval(node);
                if (*m >= index)
                        return (m);
                else
                        return (NULL);
        }
        tos = 0;
        for (;;) {
                /*
                 * If the keys differ before the current bisection node,
                 * then the search key might rollback to the earliest
                 * available bisection node or to the smallest key
                 * in the current node (if the owner is greater than the
                 * search key).
                 */
                if (pctrie_keybarr(node, index)) {
                        if (index > node->pn_owner) {
ascend:
                                KASSERT(++loops < 1000,
                                    ("pctrie_lookup_ge: too many loops"));
 
                                /*
                                 * Pop nodes from the stack until either the
                                 * stack is empty or a node that could have a
                                 * matching descendant is found.
                                 */
                                do {
                                        if (tos == 0)
                                                return (NULL);
                                        node = stack[--tos];
                                } while (pctrie_slot(index,
                                    node->pn_clev) == (PCTRIE_COUNT - 1));
 
                                /*
                                 * The following computation cannot overflow
                                 * because index's slot at the current level
                                 * is less than PCTRIE_COUNT - 1.
                                 */
                                index = pctrie_trimkey(index,
                                    node->pn_clev);
                                index += PCTRIE_UNITLEVEL(node->pn_clev);
                        } else
                                index = node->pn_owner;
                        KASSERT(!pctrie_keybarr(node, index),
                            ("pctrie_lookup_ge: keybarr failed"));
                }
                slot = pctrie_slot(index, node->pn_clev);
                child = pctrie_node_load(&node->pn_child[slot], NULL,
                    PCTRIE_LOCKED);
                if (pctrie_isleaf(child)) {
                        m = pctrie_toval(child);
                        if (*m >= index)
                                return (m);
                } else if (child != NULL)
                        goto descend;
 
                /*
                 * Look for an available edge or val within the current
                 * bisection node.
                 */
                if (slot < (PCTRIE_COUNT - 1)) {
                        inc = PCTRIE_UNITLEVEL(node->pn_clev);
                        index = pctrie_trimkey(index, node->pn_clev);
                        do {
                                index += inc;
                                slot++;
                                child = pctrie_node_load(&node->pn_child[slot],
                                    NULL, PCTRIE_LOCKED);
                                if (pctrie_isleaf(child)) {
                                        m = pctrie_toval(child);
                                        if (*m >= index)
                                                return (m);
                                } else if (child != NULL)
                                        goto descend;
                        } while (slot < (PCTRIE_COUNT - 1));
                }
                KASSERT(child == NULL || pctrie_isleaf(child),
                    ("pctrie_lookup_ge: child is radix node"));
 
                /*
                 * If a value or edge greater than the search slot is not found
                 * in the current node, ascend to the next higher-level node.
                 */
                goto ascend;
descend:
                KASSERT(node->pn_clev > 0,
                    ("pctrie_lookup_ge: pushing leaf's parent"));
                KASSERT(tos < PCTRIE_LIMIT,
                    ("pctrie_lookup_ge: stack overflow"));
                stack[tos++] = node;
                node = child;
        }
}
 
/*
 * Look up the nearest entry at a position less than or equal to index,
 * assuming access is externally synchronized by a lock.
 */
uint64_t *
pctrie_lookup_le(struct pctrie *ptree, uint64_t index)
{
        struct pctrie_node *stack[PCTRIE_LIMIT];
        uint64_t inc;
        uint64_t *m;
        struct pctrie_node *child, *node;
#ifdef INVARIANTS
        int loops = 0;
#endif
        unsigned tos;
        int slot;
 
        node = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED);
        if (node == NULL)
                return (NULL);
        else if (pctrie_isleaf(node)) {
                m = pctrie_toval(node);
                if (*m <= index)
                        return (m);
                else
                        return (NULL);
        }
        tos = 0;
        for (;;) {
                /*
                 * If the keys differ before the current bisection node,
                 * then the search key might rollback to the earliest
                 * available bisection node or to the largest key
                 * in the current node (if the owner is smaller than the
                 * search key).
                 */
                if (pctrie_keybarr(node, index)) {
                        if (index > node->pn_owner) {
                                index = node->pn_owner + PCTRIE_COUNT *
                                    PCTRIE_UNITLEVEL(node->pn_clev);
                        } else {
ascend:
                                KASSERT(++loops < 1000,
                                    ("pctrie_lookup_le: too many loops"));
 
                                /*
                                 * Pop nodes from the stack until either the
                                 * stack is empty or a node that could have a
                                 * matching descendant is found.
                                 */
                                do {
                                        if (tos == 0)
                                                return (NULL);
                                        node = stack[--tos];
                                } while (pctrie_slot(index,
                                    node->pn_clev) == 0);
 
                                /*
                                 * The following computation cannot overflow
                                 * because index's slot at the current level
                                 * is greater than 0.
                                 */
                                index = pctrie_trimkey(index,
                                    node->pn_clev);
                        }
                        index--;
                        KASSERT(!pctrie_keybarr(node, index),
                            ("pctrie_lookup_le: keybarr failed"));
                }
                slot = pctrie_slot(index, node->pn_clev);
                child = pctrie_node_load(&node->pn_child[slot], NULL,
                    PCTRIE_LOCKED);
                if (pctrie_isleaf(child)) {
                        m = pctrie_toval(child);
                        if (*m <= index)
                                return (m);
                } else if (child != NULL)
                        goto descend;
 
                /*
                 * Look for an available edge or value within the current
                 * bisection node.
                 */
                if (slot > 0) {
                        inc = PCTRIE_UNITLEVEL(node->pn_clev);
                        index |= inc - 1;
                        do {
                                index -= inc;
                                slot--;
                                child = pctrie_node_load(&node->pn_child[slot],
                                    NULL, PCTRIE_LOCKED);
                                if (pctrie_isleaf(child)) {
                                        m = pctrie_toval(child);
                                        if (*m <= index)
                                                return (m);
                                } else if (child != NULL)
                                        goto descend;
                        } while (slot > 0);
                }
                KASSERT(child == NULL || pctrie_isleaf(child),
                    ("pctrie_lookup_le: child is radix node"));
 
                /*
                 * If a value or edge smaller than the search slot is not found
                 * in the current node, ascend to the next higher-level node.
                 */
                goto ascend;
descend:
                KASSERT(node->pn_clev > 0,
                    ("pctrie_lookup_le: pushing leaf's parent"));
                KASSERT(tos < PCTRIE_LIMIT,
                    ("pctrie_lookup_le: stack overflow"));
                stack[tos++] = node;
                node = child;
        }
}
 
/*
 * Remove the specified index from the tree.
 * Panics if the key is not present.
 */
void
pctrie_remove(struct pctrie *ptree, uint64_t index, pctrie_free_t freefn)
{
        struct pctrie_node *node, *parent, *tmp;
        uint64_t *m;
        int i, slot;
 
        node = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED);
        if (pctrie_isleaf(node)) {
                m = pctrie_toval(node);
                if (*m != index)
                        panic("%s: invalid key found", __func__);
                pctrie_root_store(ptree, NULL, PCTRIE_LOCKED);
                return;
        }
        parent = NULL;
        for (;;) {
                if (node == NULL)
                        panic("pctrie_remove: impossible to locate the key");
                slot = pctrie_slot(index, node->pn_clev);
                tmp = pctrie_node_load(&node->pn_child[slot], NULL,
                    PCTRIE_LOCKED);
                if (pctrie_isleaf(tmp)) {
                        m = pctrie_toval(tmp);
                        if (*m != index)
                                panic("%s: invalid key found", __func__);
                        pctrie_node_store(&node->pn_child[slot], NULL,
                            PCTRIE_LOCKED);
                        node->pn_count--;
                        if (node->pn_count > 1)
                                break;
                        for (i = 0; i < PCTRIE_COUNT; i++) {
                                tmp = pctrie_node_load(&node->pn_child[i],
                                    NULL, PCTRIE_LOCKED);
                                if (tmp != NULL)
                                        break;
                        }
                        KASSERT(i != PCTRIE_COUNT,
                            ("%s: invalid node configuration", __func__));
                        if (parent == NULL)
                                pctrie_root_store(ptree, tmp, PCTRIE_LOCKED);
                        else {
                                slot = pctrie_slot(index, parent->pn_clev);
                                KASSERT(pctrie_node_load(
                                        &parent->pn_child[slot], NULL,
                                        PCTRIE_LOCKED) == node,
                                    ("%s: invalid child value", __func__));
                                pctrie_node_store(&parent->pn_child[slot], tmp,
                                    PCTRIE_LOCKED);
                        }
                        /*
                         * The child is still valid and we can not zero the
                         * pointer until all SMR references are gone.
                         */
                        node->pn_count--;
                        pctrie_node_put(ptree, node, freefn, i);
                        break;
                }
                parent = node;
                node = tmp;
        }
}
 
/*
 * Remove and free all the nodes from the tree.
 * This function is recursive but there is a tight control on it as the
 * maximum depth of the tree is fixed.
 */
void
pctrie_reclaim_allnodes(struct pctrie *ptree, pctrie_free_t freefn)
{
        struct pctrie_node *root;
 
        root = pctrie_root_load(ptree, NULL, PCTRIE_LOCKED);
        if (root == NULL)
                return;
        pctrie_root_store(ptree, NULL, PCTRIE_UNSERIALIZED);
        if (!pctrie_isleaf(root))
                pctrie_reclaim_allnodes_int(ptree, root, freefn);
}
 
#ifdef DDB
/*
 * Show details about the given node.
 */
DB_SHOW_COMMAND(pctrienode, db_show_pctrienode)
{
        struct pctrie_node *node, *tmp;
        int i;
 
        if (!have_addr)
                return;
        node = (struct pctrie_node *)addr;
        db_printf("node %p, owner %jx, children count %u, level %u:\n",
            (void *)node, (uintmax_t)node->pn_owner, node->pn_count,
            node->pn_clev);
        for (i = 0; i < PCTRIE_COUNT; i++) {
                tmp = pctrie_node_load(&node->pn_child[i], NULL,
                    PCTRIE_UNSERIALIZED);
                if (tmp != NULL)
                        db_printf("slot: %d, val: %p, value: %p, clev: %d\n",
                            i, (void *)tmp,
                            pctrie_isleaf(tmp) ? pctrie_toval(tmp) : NULL,
                            node->pn_clev);
        }
}
#endif /* DDB */