The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_eventhandler.c

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    1 /*-
    2  * Copyright (c) 1999 Michael Smith <msmith@freebsd.org>
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  *
   26  * $FreeBSD$
   27  */
   28 
   29 #include <sys/param.h>
   30 #include <sys/kernel.h>
   31 #include <sys/malloc.h>
   32 #include <sys/systm.h>
   33 #include <sys/eventhandler.h>
   34 
   35 MALLOC_DEFINE(M_EVENTHANDLER, "eventhandler", "Event handler records");
   36 
   37 /* List of 'slow' lists */
   38 static TAILQ_HEAD(, eventhandler_list)  eventhandler_lists;
   39 static int                              eventhandler_lists_initted = 0;
   40 
   41 struct eventhandler_entry_generic 
   42 {
   43     struct eventhandler_entry   ee;
   44     void                        (* func)(void);
   45 };
   46 
   47 /* 
   48  * Insertion is O(n) due to the priority scan, but optimises to O(1)
   49  * if all priorities are identical.
   50  */
   51 eventhandler_tag
   52 eventhandler_register(struct eventhandler_list *list, char *name, 
   53                       void *func, void *arg, int priority)
   54 {
   55     struct eventhandler_entry_generic   *eg;
   56     struct eventhandler_entry           *ep;
   57     
   58     /* avoid the need for a SYSINIT just to init the list */
   59     if (!eventhandler_lists_initted) {
   60         TAILQ_INIT(&eventhandler_lists);
   61         eventhandler_lists_initted = 1;
   62     }
   63 
   64     /* Do we need to find/create the (slow) list? */
   65     if (list == NULL) {
   66         /* look for a matching, existing list */
   67         list = eventhandler_find_list(name);
   68 
   69         /* Do we need to create the list? */
   70         if (list == NULL) {
   71             if ((list = malloc(sizeof(struct eventhandler_list) + strlen(name) + 1, 
   72                                M_EVENTHANDLER, M_NOWAIT)) == NULL)
   73                 return(NULL);
   74             list->el_flags = 0;
   75             list->el_name = (char *)list + sizeof(struct eventhandler_list);
   76             strcpy(list->el_name, name);
   77             TAILQ_INSERT_HEAD(&eventhandler_lists, list, el_link);
   78         }
   79     }
   80     if (!(list->el_flags & EHE_INITTED)) {
   81         TAILQ_INIT(&list->el_entries);
   82         list->el_flags = EHE_INITTED;
   83     }
   84     
   85     /* allocate an entry for this handler, populate it */
   86     if ((eg = malloc(sizeof(struct eventhandler_entry_generic), 
   87                      M_EVENTHANDLER, M_NOWAIT)) == NULL)
   88         return(NULL);
   89     eg->func = func;
   90     eg->ee.ee_arg = arg;
   91     eg->ee.ee_priority = priority;
   92     
   93     /* sort it into the list */
   94     for (ep = TAILQ_FIRST(&list->el_entries);
   95          ep != NULL; 
   96          ep = TAILQ_NEXT(ep, ee_link)) {
   97         if (eg->ee.ee_priority < ep->ee_priority) {
   98             TAILQ_INSERT_BEFORE(ep, &eg->ee, ee_link);
   99             break;
  100         }
  101     }
  102     if (ep == NULL)
  103         TAILQ_INSERT_TAIL(&list->el_entries, &eg->ee, ee_link);
  104     return(&eg->ee);
  105 }
  106 
  107 void
  108 eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag)
  109 {
  110     struct eventhandler_entry   *ep = tag;
  111 
  112     /* XXX insert diagnostic check here? */
  113     if (ep != NULL) {
  114         /* remove just this entry */
  115         TAILQ_REMOVE(&list->el_entries, ep, ee_link);
  116         free(ep, M_EVENTHANDLER);
  117     } else {
  118         /* remove entire list */
  119         while (!TAILQ_EMPTY(&list->el_entries)) {
  120             ep = TAILQ_FIRST(&list->el_entries);
  121             TAILQ_REMOVE(&list->el_entries, ep, ee_link);
  122             free(ep, M_EVENTHANDLER);
  123         }
  124     }
  125 }
  126 
  127 struct eventhandler_list *
  128 eventhandler_find_list(char *name)
  129 {
  130     struct eventhandler_list    *list;
  131 
  132     /* scan looking for the requested list */
  133     for (list = TAILQ_FIRST(&eventhandler_lists); 
  134          list != NULL; 
  135          list = TAILQ_NEXT(list, el_link)) {
  136         if (!strcmp(name, list->el_name))
  137             break;
  138     }
  139     return(list);
  140 }

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