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

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * 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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #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 all eventhandler 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);
    };
    
    static struct eventhandler_list *_eventhandler_find_list(const char *name);
    
    /*
     * 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);
        atomic_store_rel_int(&eventhandler_lists_initted, 1);
    }
    SYSINIT(eventhandlers, SI_SUB_EVENTHANDLER, SI_ORDER_FIRST, eventhandler_init,
        NULL);
    
    static struct eventhandler_list *
    eventhandler_find_or_create_list(const char *name)
    {
            struct eventhandler_list *list, *new_list;
    
            /* look for a matching, existing list */
            list = _eventhandler_find_list(name);
    
            /* Do we need to create the list? */
            if (list == NULL) {
                mtx_unlock(&eventhandler_mutex);
    
                new_list = malloc(sizeof(*new_list) + strlen(name) + 1,
                    M_EVENTHANDLER, M_WAITOK | M_ZERO);
    
                /* If someone else created it already, then use that one. */
                mtx_lock(&eventhandler_mutex);
                list = _eventhandler_find_list(name);
                if (list != NULL) {
                    free(new_list, M_EVENTHANDLER);
                } else {
                    CTR2(KTR_EVH, "%s: creating list \"%s\"", __func__, name);
                    list = new_list;
                    TAILQ_INIT(&list->el_entries);
                    list->el_name = (char *)(list + 1);
                    strcpy(list->el_name, name);
                    mtx_init(&list->el_lock, list->el_name, "eventhandler list",
                        MTX_DEF);
                    TAILQ_INSERT_HEAD(&eventhandler_lists, list, el_link);
                }
            }
           return (list);
   }
   
   /* 
    * Insertion is O(n) due to the priority scan, but optimises to O(1)
    * if all priorities are identical.
    */
   static eventhandler_tag
   eventhandler_register_internal(struct eventhandler_list *list,
       const char *name, eventhandler_tag epn)
   {
       struct eventhandler_entry           *ep;
       
       KASSERT(eventhandler_lists_initted, ("eventhandler registered too early"));
       KASSERT(epn != NULL, ("%s: cannot register NULL event", __func__));
   
       /* Do we need to find/create the list? */
       if (list == NULL) {
               mtx_lock(&eventhandler_mutex);
               list = eventhandler_find_or_create_list(name);
               mtx_unlock(&eventhandler_mutex);
       }
   
       KASSERT(epn->ee_priority != EHE_DEAD_PRIORITY,
           ("%s: handler for %s registered with dead priority", __func__, name));
   
       /* sort it into the list */
       CTR4(KTR_EVH, "%s: adding item %p (function %p) to \"%s\"", __func__, epn,
           ((struct eventhandler_entry_generic *)epn)->func, name);
       EHL_LOCK(list);
       TAILQ_FOREACH(ep, &list->el_entries, ee_link) {
           if (ep->ee_priority != EHE_DEAD_PRIORITY &&
               epn->ee_priority < ep->ee_priority) {
               TAILQ_INSERT_BEFORE(ep, epn, ee_link);
               break;
           }
       }
       if (ep == NULL)
           TAILQ_INSERT_TAIL(&list->el_entries, epn, ee_link);
       EHL_UNLOCK(list);
       return(epn);
   }
   
   eventhandler_tag
   eventhandler_register(struct eventhandler_list *list, const char *name, 
                         void *func, void *arg, int priority)
   {
       struct eventhandler_entry_generic   *eg;
       
       /* allocate an entry for this handler, populate it */
       eg = malloc(sizeof(struct eventhandler_entry_generic), M_EVENTHANDLER,
           M_WAITOK | M_ZERO);
       eg->func = func;
       eg->ee.ee_arg = arg;
       eg->ee.ee_priority = priority;
   
       return (eventhandler_register_internal(list, name, &eg->ee));
   }
   
   #ifdef VIMAGE
   struct eventhandler_entry_generic_vimage
   {
       struct eventhandler_entry           ee;
       vimage_iterator_func_t              func;           /* Vimage iterator function. */
       struct eventhandler_entry_vimage    v_ee;           /* Original func, arg. */
   };
   
   eventhandler_tag
   vimage_eventhandler_register(struct eventhandler_list *list, const char *name, 
       void *func, void *arg, int priority, vimage_iterator_func_t iterfunc)
   {
       struct eventhandler_entry_generic_vimage    *eg;
       
       /* allocate an entry for this handler, populate it */
       eg = malloc(sizeof(struct eventhandler_entry_generic_vimage),
           M_EVENTHANDLER, M_WAITOK | M_ZERO);
       eg->func = iterfunc;
       eg->v_ee.func = func;
       eg->v_ee.ee_arg = arg;
       eg->ee.ee_arg = &eg->v_ee;
       eg->ee.ee_priority = priority;
   
       return (eventhandler_register_internal(list, name, &eg->ee));
   }
   #endif
   
   static void
   _eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag,
       bool wait)
   {
       struct eventhandler_entry   *ep = tag;
   
       EHL_LOCK_ASSERT(list, MA_OWNED);
       if (ep != NULL) {
           /* remove just this entry */
           if (list->el_runcount == 0) {
               CTR3(KTR_EVH, "%s: removing item %p from \"%s\"", __func__, ep,
                   list->el_name);
               TAILQ_REMOVE(&list->el_entries, ep, ee_link);
               free(ep, M_EVENTHANDLER);
           } else {
               CTR3(KTR_EVH, "%s: marking item %p from \"%s\" as dead", __func__,
                   ep, list->el_name);
               ep->ee_priority = EHE_DEAD_PRIORITY;
           }
       } else {
           /* remove entire list */
           if (list->el_runcount == 0) {
               CTR2(KTR_EVH, "%s: removing all items from \"%s\"", __func__,
                   list->el_name);
               while (!TAILQ_EMPTY(&list->el_entries)) {
                   ep = TAILQ_FIRST(&list->el_entries);
                   TAILQ_REMOVE(&list->el_entries, ep, ee_link);
                   free(ep, M_EVENTHANDLER);
               }
           } else {
               CTR2(KTR_EVH, "%s: marking all items from \"%s\" as dead",
                   __func__, list->el_name);
               TAILQ_FOREACH(ep, &list->el_entries, ee_link)
                   ep->ee_priority = EHE_DEAD_PRIORITY;
           }
       }
       while (wait && list->el_runcount > 0)
               mtx_sleep(list, &list->el_lock, 0, "evhrm", 0);
       EHL_UNLOCK(list);
   }
   
   void
   eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag)
   {
   
           _eventhandler_deregister(list, tag, true);
   }
   
   void
   eventhandler_deregister_nowait(struct eventhandler_list *list,
       eventhandler_tag tag)
   {
   
           _eventhandler_deregister(list, tag, false);
   }
   
   /*
    * Internal version for use when eventhandler list is already locked.
    */
   static struct eventhandler_list *
   _eventhandler_find_list(const char *name)
   {
       struct eventhandler_list    *list;
   
       mtx_assert(&eventhandler_mutex, MA_OWNED);
       TAILQ_FOREACH(list, &eventhandler_lists, el_link) {
           if (!strcmp(name, list->el_name))
               break;
       }
       return (list);
   }
   
   /*
    * Lookup a "slow" list by name.  Returns with the list locked.
    */
   struct eventhandler_list *
   eventhandler_find_list(const char *name)
   {
       struct eventhandler_list    *list;
   
       if (!eventhandler_lists_initted)
           return(NULL);
       
       /* scan looking for the requested list */
       mtx_lock(&eventhandler_mutex);
       list = _eventhandler_find_list(name);
       if (list != NULL)
           EHL_LOCK(list);
       mtx_unlock(&eventhandler_mutex);
       
       return(list);
   }
   
   /*
    * Prune "dead" entries from an eventhandler list.
    */
   void
   eventhandler_prune_list(struct eventhandler_list *list)
   {
       struct eventhandler_entry *ep, *en;
       int pruned = 0;
   
       CTR2(KTR_EVH, "%s: pruning list \"%s\"", __func__, list->el_name);
       EHL_LOCK_ASSERT(list, MA_OWNED);
       TAILQ_FOREACH_SAFE(ep, &list->el_entries, ee_link, en) {
           if (ep->ee_priority == EHE_DEAD_PRIORITY) {
               TAILQ_REMOVE(&list->el_entries, ep, ee_link);
               free(ep, M_EVENTHANDLER);
               pruned++;
           }
       }
       if (pruned > 0)
               wakeup(list);
   }
   
   /*
    * Create (or get the existing) list so the pointer can be stored by
    * EVENTHANDLER_LIST_DEFINE.
    */
   struct eventhandler_list *
   eventhandler_create_list(const char *name)
   {
           struct eventhandler_list *list;
   
           KASSERT(eventhandler_lists_initted,
               ("eventhandler list created too early"));
   
           mtx_lock(&eventhandler_mutex);
           list = eventhandler_find_or_create_list(name);
           mtx_unlock(&eventhandler_mutex);
   
           return (list);
   }

Cache object: 308dc2a635d5d7d3317ba902a7c467e7