/*
 * Copyright (c) 2006,2012-2018 The DragonFly Project.  All rights reserved.
 *
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 *
 * 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.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
 * COPYRIGHT HOLDERS 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.
 */
/*
 * The Cache Coherency Management System (CCMS)
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <machine/limits.h>

#include <sys/spinlock2.h>

#include "hammer2_ccms.h"
#include "hammer2.h"

int ccms_debug = 0;

void
ccms_cst_init(ccms_cst_t *cst)
{
        bzero(cst, sizeof(*cst));
        hammer2_spin_init(&cst->spin, "ccmscst");
}

void
ccms_cst_uninit(ccms_cst_t *cst)
{
        KKASSERT(cst->count == 0);
        if (cst->state != CCMS_STATE_INVALID) {
                /* XXX */
        }
}

/************************************************************************
 *                          CST SUPPORT FUNCTIONS                       *
 ************************************************************************/

/*
 * Acquire local cache state & lock.  If the current thread already holds
 * the lock exclusively we bump the exclusive count, even if the thread is
 * trying to get a shared lock.
 */
void
ccms_thread_lock(ccms_cst_t *cst, ccms_state_t state)
{
        /*
         * Regardless of the type of lock requested if the current thread
         * already holds an exclusive lock we bump the exclusive count and
         * return.  This requires no spinlock.
         */
        LOCKENTER;
        if (cst->count < 0 && cst->td == curthread) {
                --cst->count;
                return;
        }

        /*
         * Otherwise use the spinlock to interlock the operation and sleep
         * as necessary.
         */
        hammer2_spin_ex(&cst->spin);
        if (state == CCMS_STATE_SHARED) {
                while (cst->count < 0 || cst->upgrade) {
                        cst->blocked = 1;
                        ssleep(cst, &cst->spin, 0, "ccmslck", hz);
                }
                ++cst->count;
                KKASSERT(cst->td == NULL);
        } else if (state == CCMS_STATE_EXCLUSIVE) {
                while (cst->count != 0 || cst->upgrade) {
                        cst->blocked = 1;
                        ssleep(cst, &cst->spin, 0, "ccmslck", hz);
                }
                cst->count = -1;
                cst->td = curthread;
        } else {
                hammer2_spin_unex(&cst->spin);
                panic("ccms_thread_lock: bad state %d\n", state);
        }
        hammer2_spin_unex(&cst->spin);
}

/*
 * Same as ccms_thread_lock() but acquires the lock non-blocking.  Returns
 * 0 on success, EBUSY on failure.
 */
int
ccms_thread_lock_nonblock(ccms_cst_t *cst, ccms_state_t state)
{
        if (cst->count < 0 && cst->td == curthread) {
                --cst->count;
                LOCKENTER;
                return(0);
        }

        hammer2_spin_ex(&cst->spin);
        if (state == CCMS_STATE_SHARED) {
                if (cst->count < 0 || cst->upgrade) {
                        hammer2_spin_unex(&cst->spin);
                        return (EBUSY);
                }
                ++cst->count;
                KKASSERT(cst->td == NULL);
        } else if (state == CCMS_STATE_EXCLUSIVE) {
                if (cst->count != 0 || cst->upgrade) {
                        hammer2_spin_unex(&cst->spin);
                        return (EBUSY);
                }
                cst->count = -1;
                cst->td = curthread;
        } else {
                hammer2_spin_unex(&cst->spin);
                panic("ccms_thread_lock_nonblock: bad state %d\n", state);
        }
        hammer2_spin_unex(&cst->spin);
        LOCKENTER;
        return(0);
}

ccms_state_t
ccms_thread_lock_temp_release(ccms_cst_t *cst)
{
        if (cst->count < 0) {
                ccms_thread_unlock(cst);
                return(CCMS_STATE_EXCLUSIVE);
        }
        if (cst->count > 0) {
                ccms_thread_unlock(cst);
                return(CCMS_STATE_SHARED);
        }
        return (CCMS_STATE_INVALID);
}

void
ccms_thread_lock_temp_restore(ccms_cst_t *cst, ccms_state_t ostate)
{
        ccms_thread_lock(cst, ostate);
}

/*
 * Temporarily upgrade a thread lock for making local structural changes.
 * No new shared or exclusive locks can be acquired by others while we are
 * upgrading, but other upgraders are allowed.
 */
ccms_state_t
ccms_thread_lock_upgrade(ccms_cst_t *cst)
{
        /*
         * Nothing to do if already exclusive
         */
        if (cst->count < 0) {
                KKASSERT(cst->td == curthread);
                return(CCMS_STATE_EXCLUSIVE);
        }

        /*
         * Convert a shared lock to exclusive.
         */
        if (cst->count > 0) {
                hammer2_spin_ex(&cst->spin);
                ++cst->upgrade;
                --cst->count;
                while (cst->count) {
                        cst->blocked = 1;
                        ssleep(cst, &cst->spin, 0, "ccmsupg", hz);
                }
                cst->count = -1;
                cst->td = curthread;
                hammer2_spin_unex(&cst->spin);
                return(CCMS_STATE_SHARED);
        }
        panic("ccms_thread_lock_upgrade: not locked");
        /* NOT REACHED */
        return(0);
}

void
ccms_thread_lock_downgrade(ccms_cst_t *cst, ccms_state_t ostate)
{
        if (ostate == CCMS_STATE_SHARED) {
                KKASSERT(cst->td == curthread);
                KKASSERT(cst->count == -1);
                hammer2_spin_ex(&cst->spin);
                --cst->upgrade;
                cst->count = 1;
                cst->td = NULL;
                if (cst->blocked) {
                        cst->blocked = 0;
                        hammer2_spin_unex(&cst->spin);
                        wakeup(cst);
                } else {
                        hammer2_spin_unex(&cst->spin);
                }
        }
        /* else nothing to do if excl->excl */
}

/*
 * Release a local thread lock
 */
void
ccms_thread_unlock(ccms_cst_t *cst)
{
        LOCKEXIT;
        if (cst->count < 0) {
                /*
                 * Exclusive
                 */
                KKASSERT(cst->td == curthread);
                if (cst->count < -1) {
                        ++cst->count;
                        return;
                }
                hammer2_spin_ex(&cst->spin);
                KKASSERT(cst->count == -1);
                cst->count = 0;
                cst->td = NULL;
                if (cst->blocked) {
                        cst->blocked = 0;
                        hammer2_spin_unex(&cst->spin);
                        wakeup(cst);
                        return;
                }
                hammer2_spin_unex(&cst->spin);
        } else if (cst->count > 0) {
                /*
                 * Shared
                 */
                hammer2_spin_ex(&cst->spin);
                if (--cst->count == 0 && cst->blocked) {
                        cst->blocked = 0;
                        hammer2_spin_unex(&cst->spin);
                        wakeup(cst);
                        return;
                }
                hammer2_spin_unex(&cst->spin);
        } else {
                panic("ccms_thread_unlock: bad zero count\n");
        }
}

void
ccms_thread_lock_setown(ccms_cst_t *cst)
{
        KKASSERT(cst->count < 0);
        cst->td = curthread;
}

/*
 * Release a previously upgraded local thread lock
 */
void
ccms_thread_unlock_upgraded(ccms_cst_t *cst, ccms_state_t ostate)
{
        if (ostate == CCMS_STATE_SHARED) {
                LOCKEXIT;
                KKASSERT(cst->td == curthread);
                KKASSERT(cst->count == -1);
                hammer2_spin_ex(&cst->spin);
                --cst->upgrade;
                cst->count = 0;
                cst->td = NULL;
                if (cst->blocked) {
                        cst->blocked = 0;
                        hammer2_spin_unex(&cst->spin);
                        wakeup(cst);
                } else {
                        hammer2_spin_unex(&cst->spin);
                }
        } else {
                ccms_thread_unlock(cst);
        }
}

int
ccms_thread_lock_owned(ccms_cst_t *cst)
{
        return(cst->count < 0 && cst->td == curthread);
}