/*      $NetBSD: subr_callback.c,v 1.7 2009/11/24 20:11:50 rmind Exp $  */

/*-
* Copyright (c)2006 YAMAMOTO Takashi,
* 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>
__KERNEL_RCSID(0, "$NetBSD: subr_callback.c,v 1.7 2009/11/24 20:11:50 rmind Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/callback.h>

void
callback_head_init(struct callback_head *ch, int ipl)
{

       memset(ch, 0, sizeof(struct callback_head));
       mutex_init(&ch->ch_lock, MUTEX_DEFAULT, ipl);
       cv_init(&ch->ch_cv, "callback");
       TAILQ_INIT(&ch->ch_q);
#if 0 /* already zero-initialized */
       ch->ch_next = NULL;
       ch->ch_nentries = 0;
       ch->ch_running = 0;
       ch->ch_flags = 0;
#endif
}

void
callback_head_destroy(struct callback_head *ch)
{

       mutex_destroy(&ch->ch_lock);
       cv_destroy(&ch->ch_cv);
}

void
callback_register(struct callback_head *ch, struct callback_entry *ce,
   void *obj, int (*fn)(struct callback_entry *, void *, void *))
{

       KASSERT(fn != NULL);
       ce->ce_func = fn;
       ce->ce_obj = obj;
       mutex_enter(&ch->ch_lock);
       TAILQ_INSERT_TAIL(&ch->ch_q, ce, ce_q);
       ch->ch_nentries++;
       mutex_exit(&ch->ch_lock);
}

void
callback_unregister(struct callback_head *ch, struct callback_entry *ce)
{

       mutex_enter(&ch->ch_lock);
       while (ch->ch_running > 0)
               cv_wait(&ch->ch_cv, &ch->ch_lock);
       if (__predict_false(ch->ch_next == ce)) {
               ch->ch_next = TAILQ_NEXT(ce, ce_q);
       }
       TAILQ_REMOVE(&ch->ch_q, ce, ce_q);
       ch->ch_nentries--;
       mutex_exit(&ch->ch_lock);
}

static int
callback_runone(struct callback_head *ch, void *arg)
{
       struct callback_entry *ce;
       int result;

       KASSERT(ch->ch_nentries > 0);
       KASSERT(ch->ch_running > 0);

       ce = ch->ch_next;
       if (ce == NULL) {
               ce = TAILQ_FIRST(&ch->ch_q);
       }
       KASSERT(ce != NULL);
       KASSERT(ce->ce_func != NULL);
       result = (*ce->ce_func)(ce, ce->ce_obj, arg);
       ch->ch_next = TAILQ_NEXT(ce, ce_q);
       return result;
}

static void
callback_run_enter(struct callback_head *ch)
{

       mutex_enter(&ch->ch_lock);
       ch->ch_running++;
       mutex_exit(&ch->ch_lock);
}

static void
callback_run_leave(struct callback_head *ch)
{

       mutex_enter(&ch->ch_lock);
       KASSERT(ch->ch_running > 0);
       ch->ch_running--;
       if (ch->ch_running == 0)
               cv_broadcast(&ch->ch_cv);
       mutex_exit(&ch->ch_lock);
}

int
callback_run_roundrobin(struct callback_head *ch, void *arg)
{
       int i;
       int n;
       int result = 0;

       callback_run_enter(ch);
       n = ch->ch_nentries;
       for (i = 0; i < n; i++) {
               result = callback_runone(ch, arg);
               if (result != CALLBACK_CHAIN_CONTINUE) {
                       break;
               }
       }
       callback_run_leave(ch);

       return result;
}