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

     /*-
      * Copyright (c) 1999 Michael Smith <msmith@freebsd.org>
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD: releng/5.0/sys/kern/subr_eventhandler.c 100370 2002-07-19 17:44:44Z mux $
     */
    
    #include <sys/param.h>
    #include <sys/kernel.h>
    #include <sys/lock.h>
    #include <sys/malloc.h>
    #include <sys/mutex.h>
    #include <sys/proc.h>
    #include <sys/systm.h>
    #include <sys/eventhandler.h>
    
    static MALLOC_DEFINE(M_EVENTHANDLER, "eventhandler", "Event handler records");
    
    /* List of 'slow' lists */
    static TAILQ_HEAD(, eventhandler_list)  eventhandler_lists;
    static int                              eventhandler_lists_initted = 0;
    static struct mtx                       eventhandler_mutex;
    
    struct eventhandler_entry_generic 
    {
        struct eventhandler_entry   ee;
        void                        (* func)(void);
    };
    
    /*
     * Initialize the eventhandler mutex and list.
     */
    static void
    eventhandler_init(void *dummy __unused)
    {
        TAILQ_INIT(&eventhandler_lists);
        mtx_init(&eventhandler_mutex, "eventhandler", NULL, MTX_DEF | MTX_RECURSE);
        eventhandler_lists_initted = 1;
    }
    SYSINIT(eventhandlers, SI_SUB_EVENTHANDLER, SI_ORDER_FIRST, eventhandler_init,
        NULL)
    
    /* 
     * Insertion is O(n) due to the priority scan, but optimises to O(1)
     * if all priorities are identical.
     */
    eventhandler_tag
    eventhandler_register(struct eventhandler_list *list, char *name, 
                          void *func, void *arg, int priority)
    {
        struct eventhandler_entry_generic   *eg;
        struct eventhandler_entry           *ep;
        
        KASSERT(eventhandler_lists_initted, ("eventhandler registered too early"));
    
        /* lock the eventhandler lists */
        mtx_lock(&eventhandler_mutex);
    
        /* Do we need to find/create the (slow) list? */
        if (list == NULL) {
            /* look for a matching, existing list */
            list = eventhandler_find_list(name);
    
            /* Do we need to create the list? */
            if (list == NULL) {
                if ((list = malloc(sizeof(struct eventhandler_list) + strlen(name)
                        + 1, M_EVENTHANDLER, M_NOWAIT)) == NULL) {
                    mtx_unlock(&eventhandler_mutex);
                    return(NULL);
                }
                list->el_flags = 0;
                bzero(&list->el_lock, sizeof(list->el_lock));
                list->el_name = (char *)list + sizeof(struct eventhandler_list);
                strcpy(list->el_name, name);
                TAILQ_INSERT_HEAD(&eventhandler_lists, list, el_link);
            }
        }
        if (!(list->el_flags & EHE_INITTED)) {
           TAILQ_INIT(&list->el_entries);
           sx_init(&list->el_lock, name);
           list->el_flags = EHE_INITTED;
       }
       mtx_unlock(&eventhandler_mutex);
       
       /* allocate an entry for this handler, populate it */
       if ((eg = malloc(sizeof(struct eventhandler_entry_generic), 
                        M_EVENTHANDLER, M_NOWAIT)) == NULL) {
           return(NULL);
       }
       eg->func = func;
       eg->ee.ee_arg = arg;
       eg->ee.ee_priority = priority;
       
       /* sort it into the list */
       EHE_LOCK(list);
       for (ep = TAILQ_FIRST(&list->el_entries);
            ep != NULL; 
            ep = TAILQ_NEXT(ep, ee_link)) {
           if (eg->ee.ee_priority < ep->ee_priority) {
               TAILQ_INSERT_BEFORE(ep, &eg->ee, ee_link);
               break;
           }
       }
       if (ep == NULL)
           TAILQ_INSERT_TAIL(&list->el_entries, &eg->ee, ee_link);
       EHE_UNLOCK(list);
       return(&eg->ee);
   }
   
   void
   eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag)
   {
       struct eventhandler_entry   *ep = tag;
   
       /* XXX insert diagnostic check here? */
       EHE_LOCK(list);
       if (ep != NULL) {
           /* remove just this entry */
           TAILQ_REMOVE(&list->el_entries, ep, ee_link);
           free(ep, M_EVENTHANDLER);
       } else {
           /* remove entire list */
           while (!TAILQ_EMPTY(&list->el_entries)) {
               ep = TAILQ_FIRST(&list->el_entries);
               TAILQ_REMOVE(&list->el_entries, ep, ee_link);
               free(ep, M_EVENTHANDLER);
           }
       }
       EHE_UNLOCK(list);
   }
   
   struct eventhandler_list *
   eventhandler_find_list(char *name)
   {
       struct eventhandler_list    *list;
   
       if (!eventhandler_lists_initted)
           return(NULL);
       
       /* scan looking for the requested list */
       mtx_lock(&eventhandler_mutex);
       for (list = TAILQ_FIRST(&eventhandler_lists); 
            list != NULL; 
            list = TAILQ_NEXT(list, el_link)) {
           if (!strcmp(name, list->el_name))
               break;
       }
       mtx_unlock(&eventhandler_mutex);
       
       return(list);
   }
   

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