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 
   27 #include <sys/cdefs.h>
   28 __FBSDID("$FreeBSD: stable/10/sys/kern/subr_eventhandler.c 205345 2010-03-19 19:51:03Z bz $");
   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 static eventhandler_tag
   72 eventhandler_register_internal(struct eventhandler_list *list,
   73     const char *name, eventhandler_tag epn)
   74 {
   75     struct eventhandler_list            *new_list;
   76     struct eventhandler_entry           *ep;
   77     
   78     KASSERT(eventhandler_lists_initted, ("eventhandler registered too early"));
   79     KASSERT(epn != NULL, ("%s: cannot register NULL event", __func__));
   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     KASSERT(epn->ee_priority != EHE_DEAD_PRIORITY,
  121         ("%s: handler for %s registered with dead priority", __func__, name));
  122 
  123     /* sort it into the list */
  124     CTR4(KTR_EVH, "%s: adding item %p (function %p) to \"%s\"", __func__, epn,
  125         ((struct eventhandler_entry_generic *)epn)->func, name);
  126     EHL_LOCK(list);
  127     TAILQ_FOREACH(ep, &list->el_entries, ee_link) {
  128         if (ep->ee_priority != EHE_DEAD_PRIORITY &&
  129             epn->ee_priority < ep->ee_priority) {
  130             TAILQ_INSERT_BEFORE(ep, epn, ee_link);
  131             break;
  132         }
  133     }
  134     if (ep == NULL)
  135         TAILQ_INSERT_TAIL(&list->el_entries, epn, ee_link);
  136     EHL_UNLOCK(list);
  137     return(epn);
  138 }
  139 
  140 eventhandler_tag
  141 eventhandler_register(struct eventhandler_list *list, const char *name, 
  142                       void *func, void *arg, int priority)
  143 {
  144     struct eventhandler_entry_generic   *eg;
  145     
  146     /* allocate an entry for this handler, populate it */
  147     eg = malloc(sizeof(struct eventhandler_entry_generic), M_EVENTHANDLER,
  148         M_WAITOK | M_ZERO);
  149     eg->func = func;
  150     eg->ee.ee_arg = arg;
  151     eg->ee.ee_priority = priority;
  152 
  153     return (eventhandler_register_internal(list, name, &eg->ee));
  154 }
  155 
  156 #ifdef VIMAGE
  157 struct eventhandler_entry_generic_vimage
  158 {
  159     struct eventhandler_entry           ee;
  160     vimage_iterator_func_t              func;           /* Vimage iterator function. */
  161     struct eventhandler_entry_vimage    v_ee;           /* Original func, arg. */
  162 };
  163 
  164 eventhandler_tag
  165 vimage_eventhandler_register(struct eventhandler_list *list, const char *name, 
  166     void *func, void *arg, int priority, vimage_iterator_func_t iterfunc)
  167 {
  168     struct eventhandler_entry_generic_vimage    *eg;
  169     
  170     /* allocate an entry for this handler, populate it */
  171     eg = malloc(sizeof(struct eventhandler_entry_generic_vimage),
  172         M_EVENTHANDLER, M_WAITOK | M_ZERO);
  173     eg->func = iterfunc;
  174     eg->v_ee.func = func;
  175     eg->v_ee.ee_arg = arg;
  176     eg->ee.ee_arg = &eg->v_ee;
  177     eg->ee.ee_priority = priority;
  178 
  179     return (eventhandler_register_internal(list, name, &eg->ee));
  180 }
  181 #endif
  182 
  183 void
  184 eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag)
  185 {
  186     struct eventhandler_entry   *ep = tag;
  187 
  188     EHL_LOCK_ASSERT(list, MA_OWNED);
  189     if (ep != NULL) {
  190         /* remove just this entry */
  191         if (list->el_runcount == 0) {
  192             CTR3(KTR_EVH, "%s: removing item %p from \"%s\"", __func__, ep,
  193                 list->el_name);
  194             TAILQ_REMOVE(&list->el_entries, ep, ee_link);
  195             free(ep, M_EVENTHANDLER);
  196         } else {
  197             CTR3(KTR_EVH, "%s: marking item %p from \"%s\" as dead", __func__,
  198                 ep, list->el_name);
  199             ep->ee_priority = EHE_DEAD_PRIORITY;
  200         }
  201     } else {
  202         /* remove entire list */
  203         if (list->el_runcount == 0) {
  204             CTR2(KTR_EVH, "%s: removing all items from \"%s\"", __func__,
  205                 list->el_name);
  206             while (!TAILQ_EMPTY(&list->el_entries)) {
  207                 ep = TAILQ_FIRST(&list->el_entries);
  208                 TAILQ_REMOVE(&list->el_entries, ep, ee_link);
  209                 free(ep, M_EVENTHANDLER);
  210             }
  211         } else {
  212             CTR2(KTR_EVH, "%s: marking all items from \"%s\" as dead",
  213                 __func__, list->el_name);
  214             TAILQ_FOREACH(ep, &list->el_entries, ee_link)
  215                 ep->ee_priority = EHE_DEAD_PRIORITY;
  216         }
  217     }
  218     while (list->el_runcount > 0)
  219             mtx_sleep(list, &list->el_lock, 0, "evhrm", 0);
  220     EHL_UNLOCK(list);
  221 }
  222 
  223 /*
  224  * Internal version for use when eventhandler list is already locked.
  225  */
  226 static struct eventhandler_list *
  227 _eventhandler_find_list(const char *name)
  228 {
  229     struct eventhandler_list    *list;
  230 
  231     mtx_assert(&eventhandler_mutex, MA_OWNED);
  232     TAILQ_FOREACH(list, &eventhandler_lists, el_link) {
  233         if (!strcmp(name, list->el_name))
  234             break;
  235     }
  236     return (list);
  237 }
  238 
  239 /*
  240  * Lookup a "slow" list by name.  Returns with the list locked.
  241  */
  242 struct eventhandler_list *
  243 eventhandler_find_list(const char *name)
  244 {
  245     struct eventhandler_list    *list;
  246 
  247     if (!eventhandler_lists_initted)
  248         return(NULL);
  249     
  250     /* scan looking for the requested list */
  251     mtx_lock(&eventhandler_mutex);
  252     list = _eventhandler_find_list(name);
  253     if (list != NULL)
  254         EHL_LOCK(list);
  255     mtx_unlock(&eventhandler_mutex);
  256     
  257     return(list);
  258 }
  259 
  260 /*
  261  * Prune "dead" entries from an eventhandler list.
  262  */
  263 void
  264 eventhandler_prune_list(struct eventhandler_list *list)
  265 {
  266     struct eventhandler_entry *ep, *en;
  267     int pruned = 0;
  268 
  269     CTR2(KTR_EVH, "%s: pruning list \"%s\"", __func__, list->el_name);
  270     EHL_LOCK_ASSERT(list, MA_OWNED);
  271     TAILQ_FOREACH_SAFE(ep, &list->el_entries, ee_link, en) {
  272         if (ep->ee_priority == EHE_DEAD_PRIORITY) {
  273             TAILQ_REMOVE(&list->el_entries, ep, ee_link);
  274             free(ep, M_EVENTHANDLER);
  275             pruned++;
  276         }
  277     }
  278     if (pruned > 0)
  279             wakeup(list);
  280 }

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