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: releng/5.1/sys/kern/subr_eventhandler.c 112111 2003-03-11 20:17:00Z jhb $
   27  */
   28 
   29 #include <sys/param.h>
   30 #include <sys/kernel.h>
   31 #include <sys/lock.h>
   32 #include <sys/malloc.h>
   33 #include <sys/mutex.h>
   34 #include <sys/proc.h>
   35 #include <sys/systm.h>
   36 #include <sys/eventhandler.h>
   37 
   38 static MALLOC_DEFINE(M_EVENTHANDLER, "eventhandler", "Event handler records");
   39 
   40 /* List of 'slow' lists */
   41 static TAILQ_HEAD(, eventhandler_list)  eventhandler_lists;
   42 static int                              eventhandler_lists_initted = 0;
   43 static struct mtx                       eventhandler_mutex;
   44 
   45 struct eventhandler_entry_generic 
   46 {
   47     struct eventhandler_entry   ee;
   48     void                        (* func)(void);
   49 };
   50 
   51 static struct eventhandler_list *_eventhandler_find_list(char *name);
   52 
   53 /*
   54  * Initialize the eventhandler mutex and list.
   55  */
   56 static void
   57 eventhandler_init(void *dummy __unused)
   58 {
   59     TAILQ_INIT(&eventhandler_lists);
   60     mtx_init(&eventhandler_mutex, "eventhandler", NULL, MTX_DEF);
   61     atomic_store_rel_int(&eventhandler_lists_initted, 1);
   62 }
   63 SYSINIT(eventhandlers, SI_SUB_EVENTHANDLER, SI_ORDER_FIRST, eventhandler_init,
   64     NULL)
   65 
   66 /* 
   67  * Insertion is O(n) due to the priority scan, but optimises to O(1)
   68  * if all priorities are identical.
   69  */
   70 eventhandler_tag
   71 eventhandler_register(struct eventhandler_list *list, char *name, 
   72                       void *func, void *arg, int priority)
   73 {
   74     struct eventhandler_list            *new_list;
   75     struct eventhandler_entry_generic   *eg;
   76     struct eventhandler_entry           *ep;
   77     
   78     KASSERT(eventhandler_lists_initted, ("eventhandler registered too early"));
   79 
   80     /* lock the eventhandler lists */
   81     mtx_lock(&eventhandler_mutex);
   82 
   83     /* Do we need to find/create the (slow) list? */
   84     if (list == NULL) {
   85         /* look for a matching, existing list */
   86         list = _eventhandler_find_list(name);
   87 
   88         /* Do we need to create the list? */
   89         if (list == NULL) {
   90             mtx_unlock(&eventhandler_mutex);
   91 
   92             new_list = malloc(sizeof(struct eventhandler_list) +
   93                 strlen(name) + 1, M_EVENTHANDLER, M_WAITOK);
   94 
   95             /* If someone else created it already, then use that one. */
   96             mtx_lock(&eventhandler_mutex);
   97             list = _eventhandler_find_list(name);
   98             if (list != NULL) {
   99                 free(new_list, M_EVENTHANDLER);
  100             } else {
  101                 CTR2(KTR_EVH, "%s: creating list \"%s\"", __func__, name);
  102                 list = new_list;
  103                 list->el_flags = 0;
  104                 list->el_runcount = 0;
  105                 bzero(&list->el_lock, sizeof(list->el_lock));
  106                 list->el_name = (char *)list + sizeof(struct eventhandler_list);
  107                 strcpy(list->el_name, name);
  108                 TAILQ_INSERT_HEAD(&eventhandler_lists, list, el_link);
  109             }
  110         }
  111     }
  112     if (!(list->el_flags & EHL_INITTED)) {
  113         TAILQ_INIT(&list->el_entries);
  114         mtx_init(&list->el_lock, name, "eventhandler list", MTX_DEF);
  115         atomic_store_rel_int(&list->el_flags, EHL_INITTED);
  116     }
  117     mtx_unlock(&eventhandler_mutex);
  118 
  119     /* allocate an entry for this handler, populate it */
  120     eg = malloc(sizeof(struct eventhandler_entry_generic), M_EVENTHANDLER,
  121         M_WAITOK | M_ZERO);
  122     eg->func = func;
  123     eg->ee.ee_arg = arg;
  124     eg->ee.ee_priority = priority;
  125     KASSERT(priority != EHE_DEAD_PRIORITY,
  126         ("%s: handler for %s registered with dead priority", __func__, name));
  127 
  128     /* sort it into the list */
  129     CTR4(KTR_EVH, "%s: adding item %p (function %p) to \"%s\"", __func__, eg,
  130         func, name);
  131     EHL_LOCK(list);
  132     TAILQ_FOREACH(ep, &list->el_entries, ee_link) {
  133         if (ep->ee_priority != EHE_DEAD_PRIORITY &&
  134             eg->ee.ee_priority < ep->ee_priority) {
  135             TAILQ_INSERT_BEFORE(ep, &eg->ee, ee_link);
  136             break;
  137         }
  138     }
  139     if (ep == NULL)
  140         TAILQ_INSERT_TAIL(&list->el_entries, &eg->ee, ee_link);
  141     EHL_UNLOCK(list);
  142     return(&eg->ee);
  143 }
  144 
  145 void
  146 eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag)
  147 {
  148     struct eventhandler_entry   *ep = tag;
  149 
  150     EHL_LOCK_ASSERT(list, MA_OWNED);
  151     if (ep != NULL) {
  152         /* remove just this entry */
  153         if (list->el_runcount == 0) {
  154             CTR3(KTR_EVH, "%s: removing item %p from \"%s\"", __func__, ep,
  155                 list->el_name);
  156             TAILQ_REMOVE(&list->el_entries, ep, ee_link);
  157             free(ep, M_EVENTHANDLER);
  158         } else {
  159             CTR3(KTR_EVH, "%s: marking item %p from \"%s\" as dead", __func__,
  160                 ep, list->el_name);
  161             ep->ee_priority = EHE_DEAD_PRIORITY;
  162         }
  163     } else {
  164         /* remove entire list */
  165         if (list->el_runcount == 0) {
  166             CTR2(KTR_EVH, "%s: removing all items from \"%s\"", __func__,
  167                 list->el_name);
  168             TAILQ_REMOVE(&list->el_entries, ep, ee_link);
  169             while (!TAILQ_EMPTY(&list->el_entries)) {
  170                 ep = TAILQ_FIRST(&list->el_entries);
  171                 TAILQ_REMOVE(&list->el_entries, ep, ee_link);
  172                 free(ep, M_EVENTHANDLER);
  173             }
  174         } else {
  175             CTR2(KTR_EVH, "%s: marking all items from \"%s\" as dead",
  176                 __func__, list->el_name);
  177             TAILQ_FOREACH(ep, &list->el_entries, ee_link)
  178                 ep->ee_priority = EHE_DEAD_PRIORITY;
  179         }
  180     }
  181     EHL_UNLOCK(list);
  182 }
  183 
  184 /*
  185  * Internal version for use when eventhandler list is already locked.
  186  */
  187 static struct eventhandler_list *
  188 _eventhandler_find_list(char *name)
  189 {
  190     struct eventhandler_list    *list;
  191 
  192     mtx_assert(&eventhandler_mutex, MA_OWNED);
  193     TAILQ_FOREACH(list, &eventhandler_lists, el_link) {
  194         if (!strcmp(name, list->el_name))
  195             break;
  196     }
  197     return (list);
  198 }
  199 
  200 /*
  201  * Lookup a "slow" list by name.  Returns with the list locked.
  202  */
  203 struct eventhandler_list *
  204 eventhandler_find_list(char *name)
  205 {
  206     struct eventhandler_list    *list;
  207 
  208     if (!eventhandler_lists_initted)
  209         return(NULL);
  210     
  211     /* scan looking for the requested list */
  212     mtx_lock(&eventhandler_mutex);
  213     list = _eventhandler_find_list(name);
  214     if (list != NULL)
  215         EHL_LOCK(list);
  216     mtx_unlock(&eventhandler_mutex);
  217     
  218     return(list);
  219 }
  220 
  221 /*
  222  * Prune "dead" entries from an eventhandler list.
  223  */
  224 void
  225 eventhandler_prune_list(struct eventhandler_list *list)
  226 {
  227     struct eventhandler_entry *ep, *en;
  228 
  229     CTR2(KTR_EVH, "%s: pruning list \"%s\"", __func__, list->el_name);
  230     EHL_LOCK_ASSERT(list, MA_OWNED);
  231     ep = TAILQ_FIRST(&list->el_entries);
  232     while (ep != NULL) {
  233         en = TAILQ_NEXT(ep, ee_link);
  234         if (ep->ee_priority == EHE_DEAD_PRIORITY) {
  235             TAILQ_REMOVE(&list->el_entries, ep, ee_link);
  236             free(ep, M_EVENTHANDLER);
  237         }
  238         ep = en;
  239     }
  240 }

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