cmd/nscd/nscd_access.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include "nscd_db.h"
#include "nscd_log.h"

/*
 * Access control structure for a piece of nscd data. This structure
 * is always tagged before the nscd data. nscd_alloc, which should
 * be used to allocate memory that requires access control or usage
 * count control, will initialize this access control structure at the
 * start of the memory returned to the caller.
 */
struct nscd_access_s {
    void        *data;          /* addr of real data */
    void        (*free_func)(nscd_acc_data_t *data); /* destructor */
    mutex_t     mutex;          /* protect this structure */
    mutex_t     *data_mutex;
    rwlock_t    *data_rwlock;
    cond_t      *data_cond;
    int     nUse;           /* usage count */
    int     type;
    int     delete;         /* no longer available */
    nscd_seq_num_t  seq_num;        /* sequence number */
};

/* size should be in multiple of 8 */
static int sizeof_access = roundup(sizeof (nscd_access_t));

#define ABORT_DUE_TO_NO_VALID_NSCD_ACCESS_DATA 0
#define ASSERT_ACCESS_DATA \
    if (access->data != data) \
        assert(ABORT_DUE_TO_NO_VALID_NSCD_ACCESS_DATA)

#define SET_ACCESS_PTR \
        access = (nscd_access_t *) \
            ((void *)((char *)data - sizeof_access))

static void _nscd_free(nscd_acc_data_t  *data);

/*
 * FUNCTION: _nscd_release
 *
 * Decrements the usage count maintained in the access data
 * tagged before 'data'. Delete the nscd data item if the delete
 * flag is set and the usage count reaches 0.
 */
void
_nscd_release(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;
    char        *me = "_nscd_release";

    if (data == NULL)
        return;

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "data = %p, access->data = %p, "
        "seq = %lld, nUse = %d\n",
        data, access->data, access->seq_num, access->nUse);
    ASSERT_ACCESS_DATA;

    (void) mutex_lock(&access->mutex);
    access->nUse--;
    if (access->nUse < 0) {
#define ACCESS_NUSE_LESS_THAN_ZERO 0
        assert(ACCESS_NUSE_LESS_THAN_ZERO);
    }
    if (access->nUse <= 0 &&
        access->delete == 1) {

        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "deleting data %p\n", access->data);
        (access->free_func)(access->data);

        /*
         * if we get here, no other thread could be
         * holding the access->mutex lock, It is safe
         * to free the memory containing the mutex
         * structure. No mutex_unlock is necessary.
         */
        _nscd_free(data);
    } else
        (void) mutex_unlock(&access->mutex);
}


/*
 * FUNCTION: _nscd_destroy
 *
 * Marks the nscd data item as to-be-deleted and then releases
 * (If the usage count happens to be zero, then _nscd_release()
 * will destroy the data.)
 *
 * Note that _nscd_destroy should only be called if the
 * caller has created the nscd data with _nscd_alloc
 * (with the exception of _nscd_set). That nscd data
 * item should be private to the caller.
 */
static void
_nscd_destroy(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;
    char        *me = "_nscd_destroy";

    if (data == NULL)
        return;

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "data = %p, access->data = %p\n", data, access->data);
    ASSERT_ACCESS_DATA;

    (void) mutex_lock(&access->mutex);
    access->delete = 1;
    (void) mutex_unlock(&access->mutex);

    _nscd_release(data);
}

/*
 * FUNCTION: _nscd_get
 *
 * Increment the usage count by one if 'data' can
 * be found in the internal address database.
 */
nscd_acc_data_t *
_nscd_get(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;
    void        *ret = data;
    rwlock_t    *addr_rwlock;
    char        *me = "_nscd_get";

    if (data == NULL)
        return (NULL);

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "data = %p, access->data = %p, seq#= %lld, nUse = %d\n",
        data, access->data, access->seq_num, access->nUse);
    ASSERT_ACCESS_DATA;

    /*
     * see if this addr is still valid,
     * if so, _nscd_is_int_addr will
     * do a read lock on the returned
     * multiple readers/single writer lock
     * to prevent the access data from being
     * deleted while it is being accessed.
     */
    if ((addr_rwlock = _nscd_is_int_addr(data,
            access->seq_num)) == NULL) {
        _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
        (me, "internal address %p not found\n", data);
        assert(addr_rwlock != NULL);
        return (NULL);
    }

    (void) mutex_lock(&access->mutex);
    if (access->delete == 1)
        ret = NULL;
    else
        access->nUse++;
    (void) mutex_unlock(&access->mutex);

    /*
     * done with the multiple readers/single writer lock
     */
    (void) rw_unlock(addr_rwlock);

    return (ret);
}

/*
 * FUNCTION: _nscd_set
 *
 * _nscd_set sets the address of a nscd data item
 * to 'new' and delete the old nscd data (old).
 * The pointer 'new' is returned.
 */
nscd_acc_data_t *
_nscd_set(
    nscd_acc_data_t *old,
    nscd_acc_data_t *new)
{
    nscd_acc_data_t *old_data, *new_data;
    char        *me = "_nscd_set";

    if (new == old)
        return (old);

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "new = %p, old = %p\n", new, old);

    old_data = _nscd_get(old);
    new_data = _nscd_get(new);

    if (old_data != new_data) {

        _nscd_destroy(old_data);
        _nscd_release(new_data);
        return (new_data);
    }

    /* if old_data == new_data, both must be NULL */
    return (NULL);
}

/*
 * FUNCTION: _nscd_rdlock
 *
 * Lock (rw_rdlock) a nscd data item for reading. The caller
 * needs to call _nscd_rw_unlock() to unlock the data item
 * when done using the data.
 */
nscd_acc_data_t *
_nscd_rdlock(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;
    void        *ret;
    char        *me = "_nscd_rdlock";

    ret = _nscd_get(data);

    if (ret == NULL)
        return (NULL);

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "data = %p, access->data = %p\n", data, access->data);
    ASSERT_ACCESS_DATA;

    assert(access->data_rwlock != NULL);

    (void) rw_rdlock(access->data_rwlock);

    return (ret);
}

/*
 * FUNCTION: _nscd_wrlock
 *
 * Lock (rw_wrlock) a nscd data item for writing. The caller
 * needs to call _nscd_rw_unlock() to unlock the data item
 * when done using the data.
 */
nscd_acc_data_t *
_nscd_wrlock(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;
    void        *ret;
    char        *me = "_nscd_wrlock";

    ret = _nscd_get(data);

    if (ret == NULL)
        return (NULL);

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "data = %p, access->data = %p\n", data, access->data);
    ASSERT_ACCESS_DATA;

    assert(access->data_rwlock != NULL);

    (void) rw_wrlock(access->data_rwlock);

    return (ret);
}

/*
 * FUNCTION: _nscd_rw_unlock
 *
 * Unlock (rw_unlock) a locked nscd data item.
 */
void
_nscd_rw_unlock(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;
    char        *me = "_nscd_rw_unlock";

    if (data == NULL)
        return;

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "data = %p, access->data = %p\n",
        data, access->data);
    ASSERT_ACCESS_DATA;

    assert(access->data_rwlock != NULL);

    (void) rw_unlock(access->data_rwlock);
    _nscd_release(data);
}

/*
 * FUNCTION: _nscd_rw_unlock_no_release
 *
 * Unlock (rw_unlock) a locked nscd data item but without release
 * it, i.e., without decrement the usage count to indicate that
 * the data item is still being referenced.
 */
void
_nscd_rw_unlock_no_release(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;

    if (data == NULL)
        return;

    SET_ACCESS_PTR;
    ASSERT_ACCESS_DATA;

    assert(access->data_rwlock != NULL);

    (void) rw_unlock(access->data_rwlock);
}

/*
 * FUNCTION: _nscd_mutex_lock
 *
 * Lock (mutex_lock) a nscd data item. The caller needs
 * to call _nscd_mutex_unlock() to unlock the data item
 * when done using the data.
 */
nscd_acc_data_t *
_nscd_mutex_lock(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;
    void        *ret;
    char        *me = "_nscd_mutex_lock";

    ret = _nscd_get(data);

    if (ret == NULL)
        return (NULL);

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "data = %p, access->data = %p\n", data, access->data);
    ASSERT_ACCESS_DATA;

    assert(access->data_mutex != NULL);

    (void) mutex_lock(access->data_mutex);

    return (ret);
}


/*
 * FUNCTION: _nscd_mutex_unlock
 *
 * Unlock a locked nscd data item (that were locked by _nscd_mutex_lock)..
 */
void
_nscd_mutex_unlock(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;
    char        *me = "_nscd_mutex_unlock";

    if (data == NULL)
        return;

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "data = %p, access->data = %p\n", data, access->data);
    ASSERT_ACCESS_DATA;

    assert(access->data_mutex != NULL);

    (void) mutex_unlock(access->data_mutex);
    _nscd_release(data);
}

/*
 * FUNCTION: _nscd_cond_wait
 *
 * Perform a condition wait with the cond_t and mutex_t associated
 * with data.
 */
void
_nscd_cond_wait(
    nscd_acc_data_t *data, cond_t *cond)
{
    nscd_access_t   *access;
    char        *me = "_nscd_cond_wait";

    if (data == NULL)
        return;

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "data = %p, access->data = %p\n", data, access->data);
    ASSERT_ACCESS_DATA;

    assert(access->data_cond != NULL && access->data_mutex != NULL);

    if (cond == NULL)
        (void) cond_wait(access->data_cond, access->data_mutex);
    else
        (void) cond_wait(cond, access->data_mutex);
}

/*
 * FUNCTION: _nscd_cond_signal
 *
 * Perform a condition signal with the cond_t associated with 'data'.
 */
void
_nscd_cond_signal(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;
    char        *me = "_nscd_cond_signal";

    if (data == NULL)
        return;

    SET_ACCESS_PTR;

    _NSCD_LOG(NSCD_LOG_ACCESS_INFO, NSCD_LOG_LEVEL_DEBUG)
    (me, "data = %p, access->data = %p\n", data, access->data);
    ASSERT_ACCESS_DATA;

    assert(access->data_cond != NULL);

    (void) cond_signal(access->data_cond);
}

/*
 * FUNCTION: _nscd_alloc
 *
 * Allocate a piece of nscd memory. 'data_free'
 * is the function to invoke to free the data
 * stored in this memory, i.e., the desctrctor.
 * 'option' indicate whether a mutex or a
 * readers/writer (or both, or none) should also
 * be allocated.
 */
nscd_acc_data_t *
_nscd_alloc(
    int     type,
    size_t      size,
    void        (*data_free)(nscd_acc_data_t *data),
    int     option)
{
    nscd_access_t   *access;
    nscd_acc_data_t *ptr;
    nscd_seq_num_t  seq_num;
    rwlock_t    *rwlock = NULL;
    mutex_t     *mutex = NULL;
    cond_t      *cond = NULL;

    if ((ptr = (nscd_acc_data_t *)calloc(1,
            size + sizeof_access)) == NULL)
        return (NULL);
    if (option & NSCD_ALLOC_MUTEX) {
        if ((mutex = (mutex_t *)calloc(1, sizeof (mutex_t))) ==
                NULL) {
            free(ptr);
            return (NULL);
        } else
            (void) mutex_init(mutex, USYNC_THREAD, NULL);
    }
    if (option & NSCD_ALLOC_RWLOCK) {
        if ((rwlock = (rwlock_t *)calloc(1, sizeof (rwlock_t))) ==
                NULL) {
            free(ptr);
            free(mutex);
            return (NULL);
        } else
            (void) rwlock_init(rwlock, USYNC_THREAD, NULL);
    }
    if (option & NSCD_ALLOC_COND) {
        if ((cond = (cond_t *)calloc(1, sizeof (cond_t))) ==
                NULL) {
            free(ptr);
            free(mutex);
            free(rwlock);
            return (NULL);
        } else
            (void) cond_init(cond, USYNC_THREAD, NULL);
    }

    /* get current sequence number */
    seq_num = _nscd_get_seq_num();

    access = (nscd_access_t *)ptr;
    access->data = (char *)ptr + sizeof_access;
    access->data_mutex = mutex;
    access->data_rwlock = rwlock;
    access->data_cond = cond;
    access->nUse = 0;
    access->delete = 0;
    access->type = type;
    access->free_func = data_free;
    access->seq_num = seq_num;

    /* add the address to the internal address database */
    if (_nscd_add_int_addr(access->data, type,
            seq_num) != NSCD_SUCCESS) {
        free(ptr);
        return (NULL);
    }

    return (access->data);
}

/*
 * FUNCTION: _nscd_free
 *
 * Free a piece of nscd memory.
 */
static void
_nscd_free(
    nscd_acc_data_t *data)
{
    nscd_access_t   *access;

    if (data == NULL)
        return;

    SET_ACCESS_PTR;
    ASSERT_ACCESS_DATA;

    /* remove the address from the internal address database */
    _nscd_del_int_addr(access->data, access->seq_num);

    if (access->data_mutex)
        free(access->data_mutex);
    if (access->data_rwlock)
        free(access->data_rwlock);
    if (access->data_cond)
        free(access->data_cond);

    (void) memset(access, 0, sizeof (*access));

    free(access);
}