ed498389de
used popped into my head during my morning commute a few weeks ago, but it is also very similar (though a bit simpler) to a patch that mini@ developed a while ago. Basically, each eventhandler list has a mutex and a run count. During an eventhandler invocation, the mutex is held while we traverse the list but is dropped while we execute actual handlers. Also, a runcount counter is incremented at the start of an invocation and decremented at the end of an invocation. Adding to the list is not a big deal since the reference of a thread currently executing the handlers remains valid across an add operation. Whether or not new handlers are executed by threads currently executing the handlers for a given list is indeterminate however. The harder case is when a handler is removed from the list. If the runcount is zero, the handler is simply removed from the list directly. If the runcount is not zero, then another thread is currently executing the handlers of this list, so the priority of this handler is set to a magic value (currently -1) to mark it as dead. Dead handlers are not executed during an invocation. If the runcount is zero after it is decremented at the end of an invocation, then a new eventhandler_prune_list() function is called to remove dead handlers from the list. Additional minor notes: - All the common parts of EVENTHANDLER_INVOKE() and EVENTHANDLER_FAST_INVOKE() have been merged into a common _EVENTHANDLER_INVOKE() macro to reduce duplication and ease maintenance. - KTR logging for eventhandlers is now available via the KTR_EVH mask. - The global eventhander_mutex is no longer recursive. Tested by: scottl (SMP i386)
241 lines
7.2 KiB
C
241 lines
7.2 KiB
C
/*-
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* Copyright (c) 1999 Michael Smith <msmith@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/systm.h>
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#include <sys/eventhandler.h>
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static MALLOC_DEFINE(M_EVENTHANDLER, "eventhandler", "Event handler records");
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/* List of 'slow' lists */
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static TAILQ_HEAD(, eventhandler_list) eventhandler_lists;
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static int eventhandler_lists_initted = 0;
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static struct mtx eventhandler_mutex;
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struct eventhandler_entry_generic
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{
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struct eventhandler_entry ee;
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void (* func)(void);
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};
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static struct eventhandler_list *_eventhandler_find_list(char *name);
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/*
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* Initialize the eventhandler mutex and list.
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*/
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static void
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eventhandler_init(void *dummy __unused)
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{
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TAILQ_INIT(&eventhandler_lists);
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mtx_init(&eventhandler_mutex, "eventhandler", NULL, MTX_DEF);
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atomic_store_rel_int(&eventhandler_lists_initted, 1);
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}
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SYSINIT(eventhandlers, SI_SUB_EVENTHANDLER, SI_ORDER_FIRST, eventhandler_init,
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NULL)
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/*
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* Insertion is O(n) due to the priority scan, but optimises to O(1)
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* if all priorities are identical.
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*/
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eventhandler_tag
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eventhandler_register(struct eventhandler_list *list, char *name,
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void *func, void *arg, int priority)
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{
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struct eventhandler_list *new_list;
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struct eventhandler_entry_generic *eg;
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struct eventhandler_entry *ep;
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KASSERT(eventhandler_lists_initted, ("eventhandler registered too early"));
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/* lock the eventhandler lists */
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mtx_lock(&eventhandler_mutex);
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/* Do we need to find/create the (slow) list? */
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if (list == NULL) {
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/* look for a matching, existing list */
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list = _eventhandler_find_list(name);
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/* Do we need to create the list? */
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if (list == NULL) {
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mtx_unlock(&eventhandler_mutex);
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new_list = malloc(sizeof(struct eventhandler_list) +
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strlen(name) + 1, M_EVENTHANDLER, M_WAITOK);
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/* If someone else created it already, then use that one. */
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mtx_lock(&eventhandler_mutex);
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list = _eventhandler_find_list(name);
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if (list != NULL) {
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free(new_list, M_EVENTHANDLER);
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} else {
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CTR2(KTR_EVH, "%s: creating list \"%s\"", __func__, name);
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list = new_list;
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list->el_flags = 0;
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list->el_runcount = 0;
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bzero(&list->el_lock, sizeof(list->el_lock));
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list->el_name = (char *)list + sizeof(struct eventhandler_list);
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strcpy(list->el_name, name);
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TAILQ_INSERT_HEAD(&eventhandler_lists, list, el_link);
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}
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}
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}
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if (!(list->el_flags & EHL_INITTED)) {
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TAILQ_INIT(&list->el_entries);
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mtx_init(&list->el_lock, name, "eventhandler list", MTX_DEF);
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atomic_store_rel_int(&list->el_flags, EHL_INITTED);
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}
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mtx_unlock(&eventhandler_mutex);
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/* allocate an entry for this handler, populate it */
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eg = malloc(sizeof(struct eventhandler_entry_generic), M_EVENTHANDLER,
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M_WAITOK | M_ZERO);
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eg->func = func;
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eg->ee.ee_arg = arg;
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eg->ee.ee_priority = priority;
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KASSERT(priority != EHE_DEAD_PRIORITY,
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("%s: handler for %s registered with dead priority", __func__, name));
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/* sort it into the list */
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CTR4(KTR_EVH, "%s: adding item %p (function %p) to \"%s\"", __func__, eg,
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func, name);
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EHL_LOCK(list);
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TAILQ_FOREACH(ep, &list->el_entries, ee_link) {
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if (ep->ee_priority != EHE_DEAD_PRIORITY &&
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eg->ee.ee_priority < ep->ee_priority) {
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TAILQ_INSERT_BEFORE(ep, &eg->ee, ee_link);
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break;
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}
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}
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if (ep == NULL)
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TAILQ_INSERT_TAIL(&list->el_entries, &eg->ee, ee_link);
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EHL_UNLOCK(list);
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return(&eg->ee);
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}
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void
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eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag)
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{
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struct eventhandler_entry *ep = tag;
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EHL_LOCK_ASSERT(list, MA_OWNED);
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if (ep != NULL) {
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/* remove just this entry */
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if (list->el_runcount == 0) {
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CTR3(KTR_EVH, "%s: removing item %p from \"%s\"", __func__, ep,
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list->el_name);
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TAILQ_REMOVE(&list->el_entries, ep, ee_link);
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free(ep, M_EVENTHANDLER);
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} else {
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CTR3(KTR_EVH, "%s: marking item %p from \"%s\" as dead", __func__,
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ep, list->el_name);
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ep->ee_priority = EHE_DEAD_PRIORITY;
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}
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} else {
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/* remove entire list */
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if (list->el_runcount == 0) {
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CTR2(KTR_EVH, "%s: removing all items from \"%s\"", __func__,
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list->el_name);
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TAILQ_REMOVE(&list->el_entries, ep, ee_link);
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while (!TAILQ_EMPTY(&list->el_entries)) {
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ep = TAILQ_FIRST(&list->el_entries);
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TAILQ_REMOVE(&list->el_entries, ep, ee_link);
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free(ep, M_EVENTHANDLER);
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}
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} else {
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CTR2(KTR_EVH, "%s: marking all items from \"%s\" as dead",
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__func__, list->el_name);
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TAILQ_FOREACH(ep, &list->el_entries, ee_link)
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ep->ee_priority = EHE_DEAD_PRIORITY;
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}
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}
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EHL_UNLOCK(list);
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}
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/*
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* Internal version for use when eventhandler list is already locked.
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*/
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static struct eventhandler_list *
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_eventhandler_find_list(char *name)
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{
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struct eventhandler_list *list;
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mtx_assert(&eventhandler_mutex, MA_OWNED);
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TAILQ_FOREACH(list, &eventhandler_lists, el_link) {
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if (!strcmp(name, list->el_name))
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break;
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}
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return (list);
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}
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/*
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* Lookup a "slow" list by name. Returns with the list locked.
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*/
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struct eventhandler_list *
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eventhandler_find_list(char *name)
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{
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struct eventhandler_list *list;
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if (!eventhandler_lists_initted)
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return(NULL);
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/* scan looking for the requested list */
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mtx_lock(&eventhandler_mutex);
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list = _eventhandler_find_list(name);
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if (list != NULL)
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EHL_LOCK(list);
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mtx_unlock(&eventhandler_mutex);
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return(list);
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}
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/*
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* Prune "dead" entries from an eventhandler list.
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*/
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void
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eventhandler_prune_list(struct eventhandler_list *list)
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{
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struct eventhandler_entry *ep, *en;
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CTR2(KTR_EVH, "%s: pruning list \"%s\"", __func__, list->el_name);
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EHL_LOCK_ASSERT(list, MA_OWNED);
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ep = TAILQ_FIRST(&list->el_entries);
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while (ep != NULL) {
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en = TAILQ_NEXT(ep, ee_link);
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if (ep->ee_priority == EHE_DEAD_PRIORITY) {
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TAILQ_REMOVE(&list->el_entries, ep, ee_link);
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free(ep, M_EVENTHANDLER);
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}
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ep = en;
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}
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}
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