subr_kobj.c

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/*-
 * Copyright (c) 2000,2003 Doug Rabson
 * 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.
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/kobj.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/sysctl.h>
#ifndef TEST
#include <sys/systm.h>
#endif

#ifdef TEST
#include "usertest.h"
#endif

static MALLOC_DEFINE(M_KOBJ, "kobj", "Kernel object structures");

#ifdef KOBJ_STATS

u_int kobj_lookup_hits;
u_int kobj_lookup_misses;

SYSCTL_UINT(_kern, OID_AUTO, kobj_hits, CTLFLAG_RD,
           &kobj_lookup_hits, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, kobj_misses, CTLFLAG_RD,
           &kobj_lookup_misses, 0, "");

#endif

static struct mtx kobj_mtx;
static int kobj_mutex_inited;
static int kobj_next_id = 1;

#define KOBJ_LOCK()             mtx_lock(&kobj_mtx)
#define KOBJ_UNLOCK()           mtx_unlock(&kobj_mtx)
#define KOBJ_ASSERT(what)       mtx_assert(&kobj_mtx, what);

SYSCTL_INT(_kern, OID_AUTO, kobj_methodcount, CTLFLAG_RD,
           &kobj_next_id, 0, "");

static void
kobj_init_mutex(void *arg)
{
        if (!kobj_mutex_inited) {
                mtx_init(&kobj_mtx, "kobj", NULL, MTX_DEF);
                kobj_mutex_inited = 1;
        }
}

SYSINIT(kobj, SI_SUB_LOCK, SI_ORDER_ANY, kobj_init_mutex, NULL);

/*
 * This method structure is used to initialise new caches. Since the
 * desc pointer is NULL, it is guaranteed never to match any read
 * descriptors.
 */
static struct kobj_method null_method = {
        0, 0,
};

int
kobj_error_method(void)
{

        return ENXIO;
}

static void
kobj_class_compile_common(kobj_class_t cls, kobj_ops_t ops)
{
        kobj_method_t *m;
        int i;

        /*
         * Don't do anything if we are already compiled.
         */
        if (cls->ops)
                return;

        /*
         * First register any methods which need it.
         */
        for (i = 0, m = cls->methods; m->desc; i++, m++) {
                if (m->desc->id == 0)
                        m->desc->id = kobj_next_id++;
        }

        /*
         * Then initialise the ops table.
         */
        for (i = 0; i < KOBJ_CACHE_SIZE; i++)
                ops->cache[i] = &null_method;
        ops->cls = cls;
        cls->ops = ops;
}

void
kobj_class_compile(kobj_class_t cls)
{
        kobj_ops_t ops;

        KOBJ_ASSERT(MA_NOTOWNED);

        /*
         * Allocate space for the compiled ops table.
         */
        ops = malloc(sizeof(struct kobj_ops), M_KOBJ, M_NOWAIT);
        if (!ops)
                panic("%s: out of memory", __func__);

        KOBJ_LOCK();
        
        /*
         * We may have lost a race for kobj_class_compile here - check
         * to make sure someone else hasn't already compiled this
         * class.
         */
        if (cls->ops) {
                KOBJ_UNLOCK();
                free(ops, M_KOBJ);
                return;
        }

        kobj_class_compile_common(cls, ops);
        KOBJ_UNLOCK();
}

void
kobj_class_compile_static(kobj_class_t cls, kobj_ops_t ops)
{

        KASSERT(kobj_mutex_inited == 0,
            ("%s: only supported during early cycles", __func__));

        /*
         * Increment refs to make sure that the ops table is not freed.
         */
        cls->refs++;
        kobj_class_compile_common(cls, ops);
}

static kobj_method_t*
kobj_lookup_method_class(kobj_class_t cls, kobjop_desc_t desc)
{
        kobj_method_t *methods = cls->methods;
        kobj_method_t *ce;

        for (ce = methods; ce && ce->desc; ce++) {
                if (ce->desc == desc) {
                        return ce;
                }
        }

        return NULL;
}

static kobj_method_t*
kobj_lookup_method_mi(kobj_class_t cls,
                      kobjop_desc_t desc)
{
        kobj_method_t *ce;
        kobj_class_t *basep;

        ce = kobj_lookup_method_class(cls, desc);
        if (ce)
                return ce;

        basep = cls->baseclasses;
        if (basep) {
                for (; *basep; basep++) {
                        ce = kobj_lookup_method_mi(*basep, desc);
                        if (ce)
                                return ce;
                }
        }

        return NULL;
}

kobj_method_t*
kobj_lookup_method(kobj_class_t cls,
                   kobj_method_t **cep,
                   kobjop_desc_t desc)
{
        kobj_method_t *ce;

#ifdef KOBJ_STATS
        /*
         * Correct for the 'hit' assumption in KOBJOPLOOKUP and record
         * a 'miss'.
         */
        kobj_lookup_hits--;
        kobj_lookup_misses++;
#endif

        ce = kobj_lookup_method_mi(cls, desc);
        if (!ce)
                ce = desc->deflt;
        *cep = ce;
        return ce;
}

void
kobj_class_free(kobj_class_t cls)
{
        void* ops = NULL;

        KOBJ_ASSERT(MA_NOTOWNED);
        KOBJ_LOCK();

        /*
         * Protect against a race between kobj_create and
         * kobj_delete.
         */
        if (cls->refs == 0) {
                /*
                 * For now we don't do anything to unregister any methods
                 * which are no longer used.
                 */

                /*
                 * Free memory and clean up.
                 */
                ops = cls->ops;
                cls->ops = NULL;
        }
        
        KOBJ_UNLOCK();

        if (ops)
                free(ops, M_KOBJ);
}

kobj_t
kobj_create(kobj_class_t cls,
            struct malloc_type *mtype,
            int mflags)
{
        kobj_t obj;

        /*
         * Allocate and initialise the new object.
         */
        obj = malloc(cls->size, mtype, mflags | M_ZERO);
        if (!obj)
                return NULL;
        kobj_init(obj, cls);

        return obj;
}

static void
kobj_init_common(kobj_t obj, kobj_class_t cls)
{

        obj->ops = cls->ops;
        cls->refs++;
}

void
kobj_init(kobj_t obj, kobj_class_t cls)
{
        KOBJ_ASSERT(MA_NOTOWNED);
  retry:
        KOBJ_LOCK();

        /*
         * Consider compiling the class' method table.
         */
        if (!cls->ops) {
                /*
                 * kobj_class_compile doesn't want the lock held
                 * because of the call to malloc - we drop the lock
                 * and re-try.
                 */
                KOBJ_UNLOCK();
                kobj_class_compile(cls);
                goto retry;
        }

        kobj_init_common(obj, cls);

        KOBJ_UNLOCK();
}

void
kobj_init_static(kobj_t obj, kobj_class_t cls)
{

        KASSERT(kobj_mutex_inited == 0,
            ("%s: only supported during early cycles", __func__));

        kobj_init_common(obj, cls);
}

void
kobj_delete(kobj_t obj, struct malloc_type *mtype)
{
        kobj_class_t cls = obj->ops->cls;
        int refs;

        /*
         * Consider freeing the compiled method table for the class
         * after its last instance is deleted. As an optimisation, we
         * should defer this for a short while to avoid thrashing.
         */
        KOBJ_ASSERT(MA_NOTOWNED);
        KOBJ_LOCK();
        cls->refs--;
        refs = cls->refs;
        KOBJ_UNLOCK();

        if (!refs)
                kobj_class_free(cls);

        obj->ops = NULL;
        if (mtype)
                free(obj, mtype);
}