lib/isc/mem.c

	mem.c revision b622f2b07bb545749d8dc131777aa9038d587560
/*
 * Copyright (C) 1997, 1998, 1999  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 */

#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>

#include <limits.h>

#include <isc/assertions.h>
#include <isc/error.h>
#include <isc/mem.h>

#ifndef ISC_SINGLETHREADED
#include <isc/mutex.h>
#include "util.h"
#else
#define LOCK(l)
#define UNLOCK(l)
#endif

#ifndef ISC_MEM_FILL
    /*
     * XXXMPA
     * We want this on during development to catch:
     * 1. some reference after free bugs.
     * 2. some failure to initalise bugs.
     */
#define ISC_MEM_FILL 1
#endif

#ifndef ISC_MEMPOOL_NAMES
/*
 * During development it is nice to be able to see names associated with
 * memory pools.
 */
#define ISC_MEMPOOL_NAMES 1
#endif


/*
 * Constants.
 */

#define DEF_MAX_SIZE        1100
#define DEF_MEM_TARGET      4096
#define ALIGNMENT_SIZE      8
#define NUM_BASIC_BLOCKS    64          /* must be > 1 */
#define TABLE_INCREMENT     1024

/*
 * Types.
 */

typedef struct {
    void *          next;
} element;

typedef struct {
    /*
     * This structure must be ALIGNMENT_SIZE bytes.
     */
    union {
        size_t      size;
        char        bytes[ALIGNMENT_SIZE];
    } u;
} size_info;

struct stats {
    unsigned long       gets;
    unsigned long       totalgets;
    unsigned long       blocks;
    unsigned long       freefrags;
};

#define MEM_MAGIC       0x4D656d43U /* MemC. */
#define VALID_CONTEXT(c)    ((c) != NULL && (c)->magic == MEM_MAGIC)

struct isc_mem {
    unsigned int        magic;
    isc_mutex_t     lock;
    isc_memalloc_t      memalloc;
    isc_memfree_t       memfree;
    void *          arg;
    size_t          max_size;
    size_t          mem_target;
    element **      freelists;
    element *       basic_blocks;
    unsigned char **    basic_table;
    unsigned int        basic_table_count;
    unsigned int        basic_table_size;
    unsigned char *     lowest;
    unsigned char *     highest;
    isc_boolean_t       checkfree;
    struct stats *      stats;
    size_t          quota;
    size_t          total;
    ISC_LIST(isc_mempool_t) pools;
};

#define MEMPOOL_MAGIC       0x4D454d70U /* MEMp. */
#define VALID_MEMPOOL(c)    ((c) != NULL && (c)->magic == MEMPOOL_MAGIC)

struct isc_mempool {
    /* always unlocked */
    unsigned int    magic;      /* magic number */
    isc_mutex_t    *lock;       /* optional lock */
    isc_mem_t      *mctx;       /* our memory context */
    /* locked via the memory context's lock */
    ISC_LINK(isc_mempool_t) link;   /* next pool in this mem context */
    /* optionally locked from here down */
    element        *items;      /* low water item list */
    size_t      size;       /* size of each item on this pool */
    unsigned int    maxalloc;   /* max number of items allowed */
    unsigned int    allocated;  /* # of items currently given out */
    unsigned int    freecount;  /* # of items on reserved list */
    unsigned int    freemax;    /* # of items allowed on free list */
    unsigned int    fillcount;  /* # of items to fetch on each fill */
    /* Stats only. */
    unsigned int    gets;       /* # of requests to this pool */
    /* Debugging only. */
#if ISC_MEMPOOL_NAMES
    char        name[16];   /* printed name in stats reports */
#endif
};

/*
 * Forward.
 */

static inline size_t        quantize(size_t);
static inline void      mem_putunlocked(isc_mem_t *, void *, size_t);
static inline void *        mem_getunlocked(isc_mem_t *, size_t);

/*
 * Private Inline-able.
 */

static inline size_t
quantize(size_t size) {
    int temp;

    /*
     * Round up the result in order to get a size big
     * enough to satisfy the request and be aligned on ALIGNMENT_SIZE
     * byte boundaries.
     */

    temp = size + (ALIGNMENT_SIZE - 1);
    return (temp - temp % ALIGNMENT_SIZE);
}

/*
 * Private.
 */

static void *
default_memalloc(void *arg, size_t size) {
    (void)arg;
    return (malloc(size));
}

static void
default_memfree(void *arg, void *ptr) {
    (void)arg;
    free(ptr);
}

/*
 * Public.
 */

isc_result_t
isc_mem_createx(size_t init_max_size, size_t target_size,
        isc_memalloc_t memalloc, isc_memfree_t memfree, void *arg,
        isc_mem_t **ctxp)
{
    isc_mem_t *ctx;

    REQUIRE(ctxp != NULL && *ctxp == NULL);
    REQUIRE(memalloc != NULL);
    REQUIRE(memfree != NULL);

    ctx = (memalloc)(arg, sizeof *ctx);
    if (ctx == NULL)
        return (ISC_R_NOMEMORY);

    if (init_max_size == 0)
        ctx->max_size = DEF_MAX_SIZE;
    else
        ctx->max_size = init_max_size;
    if (target_size == 0)
        ctx->mem_target = DEF_MEM_TARGET;
    else
        ctx->mem_target = target_size;
    ctx->memalloc = memalloc;
    ctx->memfree = memfree;
    ctx->arg = arg;
    ctx->freelists = (memalloc)(arg, ctx->max_size * sizeof (element *));
    if (ctx->freelists == NULL) {
        (memfree)(arg, ctx);
        return (ISC_R_NOMEMORY);
    }
    ctx->checkfree = ISC_TRUE;
    memset(ctx->freelists, 0,
           ctx->max_size * sizeof (element *));
    ctx->stats = (memalloc)(arg,
                (ctx->max_size+1) * sizeof (struct stats));
    if (ctx->stats == NULL) {
        (memfree)(arg, ctx->freelists);
        (memfree)(arg, ctx);
        return (ISC_R_NOMEMORY);
    }
    memset(ctx->stats, 0, (ctx->max_size + 1) * sizeof (struct stats));
    ctx->basic_blocks = NULL;
    ctx->basic_table = NULL;
    ctx->basic_table_count = 0;
    ctx->basic_table_size = 0;
    ctx->lowest = NULL;
    ctx->highest = NULL;
    if (isc_mutex_init(&ctx->lock) != ISC_R_SUCCESS) {
        (memfree)(arg, ctx->stats);
        (memfree)(arg, ctx->freelists);
        (memfree)(arg, ctx);
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_mutex_init() failed");
        return (ISC_R_UNEXPECTED);
    }
    ctx->quota = 0;
    ctx->total = 0;
    ctx->magic = MEM_MAGIC;
    ISC_LIST_INIT(ctx->pools);

    *ctxp = ctx;
    return (ISC_R_SUCCESS);
}

isc_result_t
isc_mem_create(size_t init_max_size, size_t target_size,
           isc_mem_t **ctxp)
{
    return (isc_mem_createx(init_max_size, target_size,
                default_memalloc, default_memfree, NULL,
                ctxp));
}

void
isc_mem_destroy(isc_mem_t **ctxp) {
    unsigned int i;
    isc_mem_t *ctx;

    REQUIRE(ctxp != NULL);
    ctx = *ctxp;
    REQUIRE(VALID_CONTEXT(ctx));

    ctx->magic = 0;

    INSIST(ISC_LIST_EMPTY(ctx->pools));

    if (ctx->checkfree) {
        for (i = 0; i <= ctx->max_size; i++)
            INSIST(ctx->stats[i].gets == 0);
    }

#if 0                   /* XXX brister debugging */
    for (i = 0; i < ctx->basic_table_count; i++)
        memset(ctx->basic_table[i], 0x0,
               NUM_BASIC_BLOCKS * ctx->mem_target);
#endif


    for (i = 0; i < ctx->basic_table_count; i++)
        (ctx->memfree)(ctx->arg, ctx->basic_table[i]);
    (ctx->memfree)(ctx->arg, ctx->freelists);
    (ctx->memfree)(ctx->arg, ctx->stats);
    (ctx->memfree)(ctx->arg, ctx->basic_table);

    (void)isc_mutex_destroy(&ctx->lock);
    (ctx->memfree)(ctx->arg, ctx);

    *ctxp = NULL;
}

isc_result_t
isc_mem_restore(isc_mem_t *ctx) {
    isc_result_t result;

    result = isc_mutex_init(&ctx->lock);
    if (result != ISC_R_SUCCESS)
        ctx->magic = 0;

    return (result);
}

static void
more_basic_blocks(isc_mem_t *ctx) {
    void *new;
    unsigned char *curr, *next;
    unsigned char *first, *last;
    unsigned char **table;
    unsigned int table_size;
    size_t increment;
    int i;

    /* Require: we hold the context lock. */

    /*
     * Did we hit the quota for this context?
     */
    increment = NUM_BASIC_BLOCKS * ctx->mem_target;
    if (ctx->quota != 0 && ctx->total + increment > ctx->quota)
        return;

    INSIST(ctx->basic_table_count <= ctx->basic_table_size);
    if (ctx->basic_table_count == ctx->basic_table_size) {
        table_size = ctx->basic_table_size + TABLE_INCREMENT;
        table = (ctx->memalloc)(ctx->arg,
                    table_size * sizeof (unsigned char *));
        if (table == NULL)
            return;
        if (ctx->basic_table_size != 0) {
            memcpy(table, ctx->basic_table,
                   ctx->basic_table_size *
                   sizeof (unsigned char *));
            (ctx->memfree)(ctx->arg, ctx->basic_table);
        }
        ctx->basic_table = table;
        ctx->basic_table_size = table_size;
    }

    new = (ctx->memalloc)(ctx->arg, NUM_BASIC_BLOCKS * ctx->mem_target);
    if (new == NULL)
        return;
    ctx->total += increment;
    ctx->basic_table[ctx->basic_table_count] = new;
    ctx->basic_table_count++;

    curr = new;
    next = curr + ctx->mem_target;
    for (i = 0; i < (NUM_BASIC_BLOCKS - 1); i++) {
        ((element *)curr)->next = next;
        curr = next;
        next += ctx->mem_target;
    }
    /*
     * curr is now pointing at the last block in the
     * array.
     */
    ((element *)curr)->next = NULL;
    first = new;
    last = first + NUM_BASIC_BLOCKS * ctx->mem_target - 1;
    if (first < ctx->lowest || ctx->lowest == NULL)
        ctx->lowest = first;
    if (last > ctx->highest)
        ctx->highest = last;
    ctx->basic_blocks = new;
}

void *
__isc_mem_get(isc_mem_t *ctx, size_t size)
{
    void *ret;

    REQUIRE(size > 0);
    REQUIRE(VALID_CONTEXT(ctx));

    LOCK(&ctx->lock);
    ret = mem_getunlocked(ctx, size);
    UNLOCK(&ctx->lock);

    return (ret);
}

static inline void *
mem_getunlocked(isc_mem_t *ctx, size_t size)
{
    size_t new_size = quantize(size);
    void *ret;

    if (size >= ctx->max_size || new_size >= ctx->max_size) {
        /* memget() was called on something beyond our upper limit. */
        if (ctx->quota != 0 && ctx->total + size > ctx->quota) {
            ret = NULL;
            goto done;
        }
        ret = (ctx->memalloc)(ctx->arg, size);
        if (ret != NULL) {
            ctx->total += size;
            ctx->stats[ctx->max_size].gets++;
            ctx->stats[ctx->max_size].totalgets++;
            /*
             * If we don't set new_size to size, then the
             * ISC_MEM_FILL code might write over bytes we
             * don't own.
             */
            new_size = size;
        }
        goto done;
    }

    /*
     * If there are no blocks in the free list for this size, get a chunk
     * of memory and then break it up into "new_size"-sized blocks, adding
     * them to the free list.
     */
    if (ctx->freelists[new_size] == NULL) {
        int i, frags;
        size_t total_size;
        void *new;
        unsigned char *curr, *next;

        if (ctx->basic_blocks == NULL) {
            more_basic_blocks(ctx);
            if (ctx->basic_blocks == NULL) {
                ret = NULL;
                goto done;
            }
        }
        total_size = ctx->mem_target;
        new = ctx->basic_blocks;
        ctx->basic_blocks = ctx->basic_blocks->next;
        frags = total_size / new_size;
        ctx->stats[new_size].blocks++;
        ctx->stats[new_size].freefrags += frags;
        /* Set up a linked-list of blocks of size "new_size". */
        curr = new;
        next = curr + new_size;
        for (i = 0; i < (frags - 1); i++) {
            ((element *)curr)->next = next;
            curr = next;
            next += new_size;
        }
        /* curr is now pointing at the last block in the array. */
        ((element *)curr)->next = NULL;
        ctx->freelists[new_size] = new;
    }

    /* The free list uses the "rounded-up" size "new_size": */
    ret = ctx->freelists[new_size];
    ctx->freelists[new_size] = ctx->freelists[new_size]->next;

    /*
     * The stats[] uses the _actual_ "size" requested by the
     * caller, with the caveat (in the code above) that "size" >= the
     * max. size (max_size) ends up getting recorded as a call to
     * max_size.
     */
    ctx->stats[size].gets++;
    ctx->stats[size].totalgets++;
    ctx->stats[new_size].freefrags--;

 done:

#if ISC_MEM_FILL
    if (ret != NULL)
        memset(ret, 0xbe, new_size); /* Mnemonic for "beef". */
#endif

    return (ret);
}

void
__isc_mem_put(isc_mem_t *ctx, void *mem, size_t size)
{
    REQUIRE(size > 0);
    REQUIRE(VALID_CONTEXT(ctx));

    LOCK(&ctx->lock);
    mem_putunlocked(ctx, mem, size);
    UNLOCK(&ctx->lock);
}

static inline void
mem_putunlocked(isc_mem_t *ctx, void *mem, size_t size)
{
    size_t new_size = quantize(size);

    if (size == ctx->max_size || new_size >= ctx->max_size) {
        /* memput() called on something beyond our upper limit */
#if ISC_MEM_FILL
        memset(mem, 0xde, size); /* Mnemonic for "dead". */
#endif
        (ctx->memfree)(ctx->arg, mem);
        INSIST(ctx->stats[ctx->max_size].gets != 0);
        ctx->stats[ctx->max_size].gets--;
        INSIST(size <= ctx->total);
        ctx->total -= size;
        return;
    }

#if ISC_MEM_FILL
    memset(mem, 0xde, new_size); /* Mnemonic for "dead". */
#endif

    /* The free list uses the "rounded-up" size "new_size": */
    ((element *)mem)->next = ctx->freelists[new_size];
    ctx->freelists[new_size] = (element *)mem;

    /*
     * The stats[] uses the _actual_ "size" requested by the
     * caller, with the caveat (in the code above) that "size" >= the
     * max. size (max_size) ends up getting recorded as a call to
     * max_size.
     */
    INSIST(ctx->stats[size].gets != 0);
    ctx->stats[size].gets--;
    ctx->stats[new_size].freefrags++;
}

void *
__isc_mem_getdebug(isc_mem_t *ctx, size_t size, const char *file, int line) {
    void *ptr;

    ptr = __isc_mem_get(ctx, size);
    fprintf(stderr, "%s:%d: mem_get(%p, %lu) -> %p\n", file, line,
        ctx, (unsigned long)size, ptr);
    return (ptr);
}

void
__isc_mem_putdebug(isc_mem_t *ctx, void *ptr, size_t size, const char *file,
         int line)
{
    fprintf(stderr, "%s:%d: mem_put(%p, %p, %lu)\n", file, line,
        ctx, ptr, (unsigned long)size);
    __isc_mem_put(ctx, ptr, size);
}

/*
 * Print the stats[] on the stream "out" with suitable formatting.
 */
void
isc_mem_stats(isc_mem_t *ctx, FILE *out)
{
    size_t i;
    const struct stats *s;
    const isc_mempool_t *pool;

    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    if (ctx->freelists != NULL) {
        for (i = 1; i <= ctx->max_size; i++) {
            s = &ctx->stats[i];

            if (s->totalgets == 0 && s->gets == 0)
                continue;
            fprintf(out, "%s%5d: %11lu gets, %11lu rem",
                (i == ctx->max_size) ? ">=" : "  ",
                i, s->totalgets, s->gets);
            if (s->blocks != 0)
                fprintf(out, " (%lu bl, %lu ff)",
                    s->blocks, s->freefrags);
            fputc('\n', out);
        }
    }

    /*
     * Note that since a pool can be locked now, these stats might be
     * somewhat off if the pool is in active use at the time the stats
     * are dumped.  The link fields are protected by the isc_mem_t's
     * lock, however, so walking this list and extracting integers from
     * stats fields is always safe.
     */
    pool = ISC_LIST_HEAD(ctx->pools);
    if (pool != NULL) {
        fprintf(out, "[Pool statistics]\n");
        fprintf(out, "%15s %10s %10s %10s %10s %10s %10s %10s %1s\n",
            "name", "size", "maxalloc", "allocated", "freecount",
            "freemax", "fillcount", "gets", "L");
    }
    while (pool != NULL) {
        fprintf(out, "%15s %10u %10u %10u %10u %10u %10u %10u %s\n",
            pool->name, pool->size, pool->maxalloc,
            pool->allocated, pool->freecount, pool->freemax,
            pool->fillcount, pool->gets,
            (pool->lock == NULL ? "N" : "Y"));
        pool = ISC_LIST_NEXT(pool, link);
    }

    UNLOCK(&ctx->lock);
}

isc_boolean_t
isc_mem_valid(isc_mem_t *ctx, void *ptr) {
    unsigned char *cp = ptr;
    isc_boolean_t result = ISC_FALSE;

    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    if (ctx->lowest != NULL && cp >= ctx->lowest && cp <= ctx->highest)
        result = ISC_TRUE;

    UNLOCK(&ctx->lock);

    return (result);
}

/*
 * Replacements for malloc() and free().
 */

void *
isc_mem_allocate(isc_mem_t *ctx, size_t size) {
    size_info *si;

    size += ALIGNMENT_SIZE;
    si = isc_mem_get(ctx, size);
    if (si == NULL)
        return (NULL);
    si->u.size = size;
    return (&si[1]);
}

void
isc_mem_free(isc_mem_t *ctx, void *ptr) {
    size_info *si;

    si = &(((size_info *)ptr)[-1]);
    isc_mem_put(ctx, si, si->u.size);
}

/*
 * Other useful things.
 */

char *
isc_mem_strdup(isc_mem_t *mctx, const char *s) {
    size_t len;
    char *ns;

    len = strlen(s);
    ns = isc_mem_allocate(mctx, len + 1);
    if (ns == NULL)
        return (NULL);
    strncpy(ns, s, len + 1);

    return (ns);
}

isc_boolean_t
isc_mem_destroy_check(isc_mem_t *mctx, isc_boolean_t flag) {
    isc_boolean_t oldval;

    INSIST(mctx != NULL);

    oldval = mctx->checkfree;
    mctx->checkfree = flag;
    return (oldval);
}


/*
 * Quotas
 */

void
isc_mem_setquota(isc_mem_t *ctx, size_t quota) {
    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    ctx->quota = quota;

    UNLOCK(&ctx->lock);
}

size_t
isc_mem_getquota(isc_mem_t *ctx) {
    size_t quota;

    REQUIRE(VALID_CONTEXT(ctx));
    LOCK(&ctx->lock);

    quota = ctx->quota;

    UNLOCK(&ctx->lock);

    return (quota);
}

#ifdef ISC_MEMCLUSTER_LEGACY

/*
 * Public Legacy.
 */

static isc_mem_t *default_context = NULL;

int
meminit(size_t init_max_size, size_t target_size) {
    /* need default_context lock here */
    if (default_context != NULL)
        return (-1);
    return (isc_mem_create(init_max_size, target_size, &default_context));
}

isc_mem_t *
mem_default_context(void) {
    /* need default_context lock here */
    if (default_context == NULL && meminit(0, 0) == -1)
        return (NULL);
    return (default_context);
}

void *
__memget(size_t size) {
    /* need default_context lock here */
    if (default_context == NULL && meminit(0, 0) == -1)
        return (NULL);
    return (__mem_get(default_context, size));
}

void
__memput(void *mem, size_t size) {
    /* need default_context lock here */
    REQUIRE(default_context != NULL);
    __mem_put(default_context, mem, size);
}

void *
__memget_debug(size_t size, const char *file, int line) {
    void *ptr;
    ptr = __memget(size);
    fprintf(stderr, "%s:%d: memget(%lu) -> %p\n", file, line,
        (unsigned long)size, ptr);
    return (ptr);
}

void
__memput_debug(void *ptr, size_t size, const char *file, int line) {
    fprintf(stderr, "%s:%d: memput(%p, %lu)\n", file, line,
        ptr, (unsigned long)size);
    __memput(ptr, size);
}

int
memvalid(void *ptr) {
    /* need default_context lock here */
    REQUIRE(default_context != NULL);
    return (mem_valid(default_context, ptr));
}

void
memstats(FILE *out) {
    /* need default_context lock here */
    REQUIRE(default_context != NULL);
    mem_stats(default_context, out);
}

#endif /* ISC_MEMCLUSTER_LEGACY */


/*
 * Memory pool stuff
 */


#if 0
/*
 * Free all but "n" items from the pool's free list.  If n == 0, all items
 * will be returned to the mctx.
 */
static void
mempool_release(isc_mempool_t *mpctx, unsigned int n)
{
    isc_mem_t *mctx;
    element *item;
    element *next;
    unsigned int count;

    mctx = mpctx->mctx;

    if (mpctx->freecount <= n)
        return;

    INSIST(mpctx->items != NULL);
    item = mpctx->items;
    for (count = 0 ; count < n ; count++) {
        item = item->next;
        INSIST(item != NULL);
    }

    /*
     * All remaining items are to be freed.  Lock the context once,
     * free them all, and unlock the context.
     */
    LOCK(&mctx->lock);
    do {
        next = item->next;
        mem_putunlocked(mctx, item, mpctx->size);
        INSIST(mpctx->freecount > 0);
        mpctx->freecount--;
        item = next;
    } while (item != NULL);
    UNLOCK(&mctx->lock);
}
#endif

/*
 * Release all items on the free list.  No locking is done, the memory
 * context must be locked, and the pool if needed.
 */
static void
mempool_releaseall(isc_mempool_t *mpctx)
{
    isc_mem_t *mctx;
    element *item;
    element *next;

    mctx = mpctx->mctx;

    if (mpctx->freecount == 0)
        return;

    INSIST(mpctx->items != NULL);
    item = mpctx->items;

    do {
        next = item->next;
        mem_putunlocked(mctx, item, mpctx->size);
        INSIST(mpctx->freecount > 0);
        mpctx->freecount--;
        item = next;
    } while (item != NULL);
}

isc_result_t
isc_mempool_create(isc_mem_t *mctx, size_t size, isc_mempool_t **mpctxp)
{
    isc_mempool_t *mpctx;

    REQUIRE(VALID_CONTEXT(mctx));
    REQUIRE(size > 0);
    REQUIRE(mpctxp != NULL && *mpctxp == NULL);

    /*
     * Allocate space for this pool, initialize values, and if all works
     * well, attach to the memory context.
     */
    LOCK(&mctx->lock);

    mpctx = mem_getunlocked(mctx, sizeof(isc_mempool_t));
    if (mpctx == NULL) {
        UNLOCK(&mctx->lock);
        return (ISC_R_NOMEMORY);
    }

    mpctx->magic = MEMPOOL_MAGIC;
    mpctx->lock = NULL;
    mpctx->mctx = mctx;
    mpctx->size = size;
    mpctx->maxalloc = UINT_MAX;
    mpctx->allocated = 0;
    mpctx->freecount = 0;
    mpctx->freemax = 1;
    mpctx->fillcount = 1;
    mpctx->gets = 0;
#if ISC_MEMPOOL_NAMES
    mpctx->name[0] = 0;
#endif
    mpctx->items = NULL;

    *mpctxp = mpctx;

    ISC_LIST_APPEND(mctx->pools, mpctx, link);

    UNLOCK(&mctx->lock);

    return (ISC_R_SUCCESS);
}

void
isc_mempool_setname(isc_mempool_t *mpctx, char *name)
{
    REQUIRE(name != NULL);

#if ISC_MEMPOOL_NAMES
    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    memset(mpctx->name, 0, sizeof(mpctx->name));
    strncpy(mpctx->name, name, sizeof(mpctx->name) - 1);

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
#else
    (void)mpctx;
    (void)name;
#endif
}

void
isc_mempool_destroy(isc_mempool_t **mpctxp)
{
    isc_mempool_t *mpctx;
    isc_mem_t *mctx;
    isc_mutex_t *lock;

    REQUIRE(mpctxp != NULL);
    mpctx = *mpctxp;
    REQUIRE(VALID_MEMPOOL(mpctx));
    REQUIRE(mpctx->allocated == 0);

    mctx = mpctx->mctx;

    lock = mpctx->lock;

    if (lock != NULL)
        LOCK(lock);

    LOCK(&mctx->lock);

    /*
     * Return any items on the free list
     */
    mempool_releaseall(mpctx);

    /*
     * Remove our linked list entry from the memory context.
     */
    ISC_LIST_UNLINK(mctx->pools, mpctx, link);

    mpctx->magic = 0;

    mem_putunlocked(mpctx->mctx, mpctx, sizeof(isc_mempool_t));

    UNLOCK(&mctx->lock);

    if (lock != NULL)
        UNLOCK(lock);

    *mpctxp = NULL;
}

void
isc_mempool_associatelock(isc_mempool_t *mpctx, isc_mutex_t *lock)
{
    REQUIRE(VALID_MEMPOOL(mpctx));
    REQUIRE(mpctx->lock == NULL);
    REQUIRE(lock != NULL);

    mpctx->lock = lock;
}

void *
__isc_mempool_get(isc_mempool_t *mpctx)
{
    element *item;
    isc_mem_t *mctx;
    unsigned int i;

    REQUIRE(VALID_MEMPOOL(mpctx));

    mctx = mpctx->mctx;

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    /*
     * Don't let the caller go over quota
     */
    if (mpctx->allocated >= mpctx->maxalloc) {
        item = NULL;
        goto out;
    }

    /*
     * if we have a free list item, return the first here
     */
    item = mpctx->items;
    if (item != NULL) {
        mpctx->items = item->next;
        INSIST(mpctx->freecount > 0);
        mpctx->freecount--;
        mpctx->gets++;
        mpctx->allocated++;
        goto out;
    }

    /*
     * We need to dip into the well.  Lock the memory context here and
     * fill up our free list.
     */
    LOCK(&mctx->lock);
    for (i = 0 ; i < mpctx->fillcount ; i++) {
        item = mem_getunlocked(mctx, mpctx->size);
        if (item == NULL)
            break;
        item->next = mpctx->items;
        mpctx->items = item;
        mpctx->freecount++;
    }
    UNLOCK(&mctx->lock);

    /*
     * If we didn't get any items, return NULL.
     */
    item = mpctx->items;
    if (item == NULL)
        goto out;

    mpctx->items = item->next;
    mpctx->freecount--;
    mpctx->gets++;
    mpctx->allocated++;

 out:
    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (item);
}

void
__isc_mempool_put(isc_mempool_t *mpctx, void *mem)
{
    isc_mem_t *mctx;
    element *item;

    REQUIRE(VALID_MEMPOOL(mpctx));
    REQUIRE(mem != NULL);

    mctx = mpctx->mctx;

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    INSIST(mpctx->allocated > 0);
    mpctx->allocated--;

    /*
     * If our free list is full, return this to the mctx directly.
     */
    if (mpctx->freecount >= mpctx->freemax) {
        __isc_mem_put(mctx, mem, mpctx->size);
        if (mpctx->lock != NULL)
            UNLOCK(mpctx->lock);
        return;
    }

    /*
     * Otherwise, attach it to our free list and bump the counter.
     */
    mpctx->freecount++;
    item = (element *)mem;
    item->next = mpctx->items;
    mpctx->items = item;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
}

void *
__isc_mempool_getdebug(isc_mempool_t *mpctx,
               const char *file, int line)
{
    void *ptr;

    ptr = __isc_mempool_get(mpctx);
    fprintf(stderr, "%s:%d: mempool_get(%p) -> %p\n", file, line,
        mpctx, ptr);

    return (ptr);
}

void
__isc_mempool_putdebug(isc_mempool_t *mpctx, void *ptr,
               const char *file, int line)
{
    fprintf(stderr, "%s:%d: mempool_put(%p, %p)\n", file, line,
        mpctx, ptr);
    __isc_mempool_put(mpctx, ptr);
}

/*
 * Quotas
 */

void
isc_mempool_setfreemax(isc_mempool_t *mpctx, unsigned int limit)
{
    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    mpctx->freemax = limit;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
}

unsigned int
isc_mempool_getfreemax(isc_mempool_t *mpctx)
{
    unsigned int freemax;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    freemax = mpctx->freemax;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (freemax);
}

unsigned int
isc_mempool_getfreecount(isc_mempool_t *mpctx)
{
    unsigned int freecount;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    freecount = mpctx->freecount;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (freecount);
}

void
isc_mempool_setmaxalloc(isc_mempool_t *mpctx, unsigned int limit)
{
    REQUIRE(limit > 0);

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    mpctx->maxalloc = limit;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
}

unsigned int
isc_mempool_getmaxalloc(isc_mempool_t *mpctx)
{
    unsigned int maxalloc;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    maxalloc = mpctx->maxalloc;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (maxalloc);
}

unsigned int
isc_mempool_getallocated(isc_mempool_t *mpctx)
{
    unsigned int allocated;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    allocated = mpctx->allocated;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (allocated);
}

void
isc_mempool_setfillcount(isc_mempool_t *mpctx, unsigned int limit)
{
    REQUIRE(limit > 0);
    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    mpctx->fillcount = limit;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);
}

unsigned int
isc_mempool_getfillcount(isc_mempool_t *mpctx)
{
    unsigned int fillcount;

    REQUIRE(VALID_MEMPOOL(mpctx));

    if (mpctx->lock != NULL)
        LOCK(mpctx->lock);

    fillcount = mpctx->fillcount;

    if (mpctx->lock != NULL)
        UNLOCK(mpctx->lock);

    return (fillcount);
}