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      1 /*	$NetBSD: subr_callback.c,v 1.7 2009/11/24 20:11:50 rmind Exp $	*/
      2 
      3 /*-
      4  * Copyright (c)2006 YAMAMOTO Takashi,
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26  * SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: subr_callback.c,v 1.7 2009/11/24 20:11:50 rmind Exp $");
     31 
     32 #include <sys/param.h>
     33 #include <sys/systm.h>
     34 #include <sys/proc.h>
     35 #include <sys/callback.h>
     36 
     37 void
     38 callback_head_init(struct callback_head *ch, int ipl)
     39 {
     40 
     41 	memset(ch, 0, sizeof(struct callback_head));
     42 	mutex_init(&ch->ch_lock, MUTEX_DEFAULT, ipl);
     43 	cv_init(&ch->ch_cv, "callback");
     44 	TAILQ_INIT(&ch->ch_q);
     45 #if 0 /* already zero-initialized */
     46 	ch->ch_next = NULL;
     47 	ch->ch_nentries = 0;
     48 	ch->ch_running = 0;
     49 	ch->ch_flags = 0;
     50 #endif
     51 }
     52 
     53 void
     54 callback_head_destroy(struct callback_head *ch)
     55 {
     56 
     57 	mutex_destroy(&ch->ch_lock);
     58 	cv_destroy(&ch->ch_cv);
     59 }
     60 
     61 void
     62 callback_register(struct callback_head *ch, struct callback_entry *ce,
     63     void *obj, int (*fn)(struct callback_entry *, void *, void *))
     64 {
     65 
     66 	KASSERT(fn != NULL);
     67 	ce->ce_func = fn;
     68 	ce->ce_obj = obj;
     69 	mutex_enter(&ch->ch_lock);
     70 	TAILQ_INSERT_TAIL(&ch->ch_q, ce, ce_q);
     71 	ch->ch_nentries++;
     72 	mutex_exit(&ch->ch_lock);
     73 }
     74 
     75 void
     76 callback_unregister(struct callback_head *ch, struct callback_entry *ce)
     77 {
     78 
     79 	mutex_enter(&ch->ch_lock);
     80 	while (ch->ch_running > 0)
     81 		cv_wait(&ch->ch_cv, &ch->ch_lock);
     82 	if (__predict_false(ch->ch_next == ce)) {
     83 		ch->ch_next = TAILQ_NEXT(ce, ce_q);
     84 	}
     85 	TAILQ_REMOVE(&ch->ch_q, ce, ce_q);
     86 	ch->ch_nentries--;
     87 	mutex_exit(&ch->ch_lock);
     88 }
     89 
     90 static int
     91 callback_runone(struct callback_head *ch, void *arg)
     92 {
     93 	struct callback_entry *ce;
     94 	int result;
     95 
     96 	KASSERT(ch->ch_nentries > 0);
     97 	KASSERT(ch->ch_running > 0);
     98 
     99 	ce = ch->ch_next;
    100 	if (ce == NULL) {
    101 		ce = TAILQ_FIRST(&ch->ch_q);
    102 	}
    103 	KASSERT(ce != NULL);
    104 	KASSERT(ce->ce_func != NULL);
    105 	result = (*ce->ce_func)(ce, ce->ce_obj, arg);
    106 	ch->ch_next = TAILQ_NEXT(ce, ce_q);
    107 	return result;
    108 }
    109 
    110 static void
    111 callback_run_enter(struct callback_head *ch)
    112 {
    113 
    114 	mutex_enter(&ch->ch_lock);
    115 	ch->ch_running++;
    116 	mutex_exit(&ch->ch_lock);
    117 }
    118 
    119 static void
    120 callback_run_leave(struct callback_head *ch)
    121 {
    122 
    123 	mutex_enter(&ch->ch_lock);
    124 	KASSERT(ch->ch_running > 0);
    125 	ch->ch_running--;
    126 	if (ch->ch_running == 0)
    127 		cv_broadcast(&ch->ch_cv);
    128 	mutex_exit(&ch->ch_lock);
    129 }
    130 
    131 int
    132 callback_run_roundrobin(struct callback_head *ch, void *arg)
    133 {
    134 	int i;
    135 	int n;
    136 	int result = 0;
    137 
    138 	callback_run_enter(ch);
    139 	n = ch->ch_nentries;
    140 	for (i = 0; i < n; i++) {
    141 		result = callback_runone(ch, arg);
    142 		if (result != CALLBACK_CHAIN_CONTINUE) {
    143 			break;
    144 		}
    145 	}
    146 	callback_run_leave(ch);
    147 
    148 	return result;
    149 }
    150