sys/kern/subr_eventhandler.c

   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
  27 #include <sys/cdefs.h>
  28 __FBSDID("$FreeBSD$");
  29
  30 #include <sys/param.h>
  31 #include <sys/kernel.h>
  32 #include <sys/lock.h>
  33 #include <sys/malloc.h>
  34 #include <sys/mutex.h>
  35 #include <sys/proc.h>
  36 #include <sys/systm.h>
  37 #include <sys/eventhandler.h>
  38
  39 static MALLOC_DEFINE(M_EVENTHANDLER, "eventhandler", "Event handler records");
  40
  41 /* List of 'slow' lists */
  42 static TAILQ_HEAD(, eventhandler_list)  eventhandler_lists;
  43 static int                              eventhandler_lists_initted = 0;
  44 static struct mtx                       eventhandler_mutex;
  45
  46 struct eventhandler_entry_generic
  47 {
  48     struct eventhandler_entry   ee;
  49     void                        (* func)(void);
  50 };
  51
  52 static struct eventhandler_list *_eventhandler_find_list(const char *name);
  53
  54 /*
  55  * Initialize the eventhandler mutex and list.
  56  */
  57 static void
  58 eventhandler_init(void *dummy __unused)
  59 {
  60     TAILQ_INIT(&eventhandler_lists);
  61     mtx_init(&eventhandler_mutex, "eventhandler", NULL, MTX_DEF);
  62     atomic_store_rel_int(&eventhandler_lists_initted, 1);
  63 }
  64 SYSINIT(eventhandlers, SI_SUB_EVENTHANDLER, SI_ORDER_FIRST, eventhandler_init,
  65     NULL);
  66
  67 /*
  68  * Insertion is O(n) due to the priority scan, but optimises to O(1)
  69  * if all priorities are identical.
  70  */
  71 eventhandler_tag
  72 eventhandler_register(struct eventhandler_list *list, const char *name,
  73                       void *func, void *arg, int priority)
  74 {
  75     struct eventhandler_list            *new_list;
  76     struct eventhandler_entry_generic   *eg;
  77     struct eventhandler_entry           *ep;
  78
  79     KASSERT(eventhandler_lists_initted, ("eventhandler registered too early"));
  80
  81     /* lock the eventhandler lists */
  82     mtx_lock(&eventhandler_mutex);
  83
  84     /* Do we need to find/create the (slow) list? */
  85     if (list == NULL) {
  86         /* look for a matching, existing list */
  87         list = _eventhandler_find_list(name);
  88
  89         /* Do we need to create the list? */
  90         if (list == NULL) {
  91             mtx_unlock(&eventhandler_mutex);
  92
  93             new_list = malloc(sizeof(struct eventhandler_list) +
  94                 strlen(name) + 1, M_EVENTHANDLER, M_WAITOK);
  95
  96             /* If someone else created it already, then use that one. */
  97             mtx_lock(&eventhandler_mutex);
  98             list = _eventhandler_find_list(name);
  99             if (list != NULL) {
 100                 free(new_list, M_EVENTHANDLER);
 101             } else {
 102                 CTR2(KTR_EVH, "%s: creating list \"%s\"", __func__, name);
 103                 list = new_list;
 104                 list->el_flags = 0;
 105                 list->el_runcount = 0;
 106                 bzero(&list->el_lock, sizeof(list->el_lock));
 107                 list->el_name = (char *)list + sizeof(struct eventhandler_list);
 108                 strcpy(list->el_name, name);
 109                 TAILQ_INSERT_HEAD(&eventhandler_lists, list, el_link);
 110             }
 111         }
 112     }
 113     if (!(list->el_flags & EHL_INITTED)) {
 114         TAILQ_INIT(&list->el_entries);
 115         mtx_init(&list->el_lock, name, "eventhandler list", MTX_DEF);
 116         atomic_store_rel_int(&list->el_flags, EHL_INITTED);
 117     }
 118     mtx_unlock(&eventhandler_mutex);
 119
 120     /* allocate an entry for this handler, populate it */
 121     eg = malloc(sizeof(struct eventhandler_entry_generic), M_EVENTHANDLER,
 122         M_WAITOK | M_ZERO);
 123     eg->func = func;
 124     eg->ee.ee_arg = arg;
 125     eg->ee.ee_priority = priority;
 126     KASSERT(priority != EHE_DEAD_PRIORITY,
 127         ("%s: handler for %s registered with dead priority", __func__, name));
 128
 129     /* sort it into the list */
 130     CTR4(KTR_EVH, "%s: adding item %p (function %p) to \"%s\"", __func__, eg,
 131         func, name);
 132     EHL_LOCK(list);
 133     TAILQ_FOREACH(ep, &list->el_entries, ee_link) {
 134         if (ep->ee_priority != EHE_DEAD_PRIORITY &&
 135             eg->ee.ee_priority < ep->ee_priority) {
 136             TAILQ_INSERT_BEFORE(ep, &eg->ee, ee_link);
 137             break;
 138         }
 139     }
 140     if (ep == NULL)
 141         TAILQ_INSERT_TAIL(&list->el_entries, &eg->ee, ee_link);
 142     EHL_UNLOCK(list);
 143     return(&eg->ee);
 144 }
 145
 146 void
 147 eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag)
 148 {
 149     struct eventhandler_entry   *ep = tag;
 150
 151     EHL_LOCK_ASSERT(list, MA_OWNED);
 152     if (ep != NULL) {
 153         /* remove just this entry */
 154         if (list->el_runcount == 0) {
 155             CTR3(KTR_EVH, "%s: removing item %p from \"%s\"", __func__, ep,
 156                 list->el_name);
 157             TAILQ_REMOVE(&list->el_entries, ep, ee_link);
 158             free(ep, M_EVENTHANDLER);
 159         } else {
 160             CTR3(KTR_EVH, "%s: marking item %p from \"%s\" as dead", __func__,
 161                 ep, list->el_name);
 162             ep->ee_priority = EHE_DEAD_PRIORITY;
 163         }
 164     } else {
 165         /* remove entire list */
 166         if (list->el_runcount == 0) {
 167             CTR2(KTR_EVH, "%s: removing all items from \"%s\"", __func__,
 168                 list->el_name);
 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(const 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(const 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 }