acache.c

非常好的dns解析软件

	for (i = 0; i < DEFAULT_ACACHE_ENTRY_LOCK_COUNT; i++)
		ACACHE_DESTROYLOCK(&acache->entrylocks[i]);
	isc_mem_put(acache->mctx, acache->entrylocks,
		    sizeof(*acache->entrylocks) *
		    DEFAULT_ACACHE_ENTRY_LOCK_COUNT);

	DESTROYLOCK(&acache->cleaner.lock);

	DESTROYLOCK(&acache->lock);
	acache->magic = 0;

	isc_mem_putanddetach(&acache->mctx, acache, sizeof(*acache));
}

static inline isc_result_t
finddbent(dns_acache_t *acache, dns_db_t *db, dbentry_t **dbentryp) {
	int bucket;
	dbentry_t *dbentry;

	REQUIRE(DNS_ACACHE_VALID(acache));
	REQUIRE(db != NULL);
	REQUIRE(dbentryp != NULL && *dbentryp == NULL);

	/*
	 * The caller must be holding the acache lock.
	 */

	bucket = isc_hash_calc((const unsigned char *)&db,
			       sizeof(db), ISC_TRUE) % DBBUCKETS;

	for (dbentry = ISC_LIST_HEAD(acache->dbbucket[bucket]);
	     dbentry != NULL;
	     dbentry = ISC_LIST_NEXT(dbentry, link)) {
		if (dbentry->db == db)
			break;
	}

	*dbentryp = dbentry;

	if (dbentry == NULL)
		return (ISC_R_NOTFOUND);
	else
		return (ISC_R_SUCCESS);
}

static inline void
clear_entry(dns_acache_t *acache, dns_acacheentry_t *entry) {
	REQUIRE(DNS_ACACHE_VALID(acache));
	REQUIRE(DNS_ACACHEENTRY_VALID(entry));

	/*
	 * The caller must be holing the entry lock.
	 */

	if (entry->foundname) {
		dns_rdataset_t *rdataset, *rdataset_next;

		for (rdataset = ISC_LIST_HEAD(entry->foundname->list);
		     rdataset != NULL;
		     rdataset = rdataset_next) {
			rdataset_next = ISC_LIST_NEXT(rdataset, link);
			ISC_LIST_UNLINK(entry->foundname->list,
					rdataset, link);
			dns_rdataset_disassociate(rdataset);
			isc_mem_put(acache->mctx, rdataset, sizeof(*rdataset));
		}
		if (dns_name_dynamic(entry->foundname))
			dns_name_free(entry->foundname, acache->mctx);
		isc_mem_put(acache->mctx, entry->foundname,
			    sizeof(*entry->foundname)); 
		entry->foundname = NULL;
	}

	if (entry->node != NULL) {
		INSIST(entry->db != NULL);
		dns_db_detachnode(entry->db, &entry->node);
	}
	if (entry->version != NULL) {
		INSIST(entry->db != NULL);
		dns_db_closeversion(entry->db, &entry->version, ISC_FALSE);
	}
	if (entry->db != NULL)
		dns_db_detach(&entry->db);
	if (entry->zone != NULL)
		dns_zone_detach(&entry->zone);

	if (entry->origdb != NULL)
		dns_db_detach(&entry->origdb);
}

static isc_result_t
acache_cleaner_init(dns_acache_t *acache, isc_timermgr_t *timermgr,
		    acache_cleaner_t *cleaner)
{
	int result;

	ATRACE("acache cleaner init");

	result = isc_mutex_init(&cleaner->lock);
	if (result != ISC_R_SUCCESS)
		goto fail;

	cleaner->increment = DNS_ACACHE_CLEANERINCREMENT;
	cleaner->state = cleaner_s_idle;
	cleaner->acache = acache;
	cleaner->overmem = ISC_FALSE;

	cleaner->cleaning_timer = NULL;
	cleaner->resched_event = NULL;
	cleaner->overmem_event = NULL;
	cleaner->current_entry = NULL;

	if (timermgr != NULL) {
		cleaner->acache->live_cleaners++;
		
		result = isc_task_onshutdown(acache->task,
					     acache_cleaner_shutdown_action,
					     acache);
		if (result != ISC_R_SUCCESS) {
			UNEXPECTED_ERROR(__FILE__, __LINE__,
					 "acache cleaner: "
					 "isc_task_onshutdown() failed: %s",
					 dns_result_totext(result));
			goto cleanup;
		}

		cleaner->cleaning_interval = 0; /* Initially turned off. */
		isc_stdtime_get(&cleaner->last_cleanup_time);
		result = isc_timer_create(timermgr, isc_timertype_inactive,
					  NULL, NULL,
					  acache->task,
					  acache_cleaning_timer_action,
					  cleaner, &cleaner->cleaning_timer);
		if (result != ISC_R_SUCCESS) {
			UNEXPECTED_ERROR(__FILE__, __LINE__,
					 "isc_timer_create() failed: %s",
					 dns_result_totext(result));
			result = ISC_R_UNEXPECTED;
			goto cleanup;
		}

		cleaner->resched_event =
			isc_event_allocate(acache->mctx, cleaner,
					   DNS_EVENT_ACACHECLEAN,
					   acache_incremental_cleaning_action,
					   cleaner, sizeof(isc_event_t));
		if (cleaner->resched_event == NULL) {
			result = ISC_R_NOMEMORY;
			goto cleanup;
		}

		cleaner->overmem_event =
			isc_event_allocate(acache->mctx, cleaner,
					   DNS_EVENT_ACACHEOVERMEM,
					   acache_overmem_cleaning_action,
					   cleaner, sizeof(isc_event_t));
		if (cleaner->overmem_event == NULL) {
			result = ISC_R_NOMEMORY;
			goto cleanup;
		}
	}

	return (ISC_R_SUCCESS);

 cleanup:
	if (cleaner->overmem_event != NULL)
		isc_event_free(&cleaner->overmem_event);
	if (cleaner->resched_event != NULL)
		isc_event_free(&cleaner->resched_event);
	if (cleaner->cleaning_timer != NULL)
		isc_timer_detach(&cleaner->cleaning_timer);
	cleaner->acache->live_cleaners--;
	DESTROYLOCK(&cleaner->lock);
 fail:
	return (result);
}

static void
begin_cleaning(acache_cleaner_t *cleaner) {
	dns_acacheentry_t *head;
	dns_acache_t *acache = cleaner->acache;

	/*
	 * This function does not have to lock the cleaner, since critical
	 * parameters (except current_entry, which is locked by acache lock,)
	 * are only used in a single task context.
	 */

	REQUIRE(CLEANER_IDLE(cleaner));
	INSIST(DNS_ACACHE_VALID(acache));
	INSIST(cleaner->current_entry == NULL);

	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
		      DNS_LOGMODULE_ACACHE, ISC_LOG_DEBUG(1),
		      "begin acache cleaning, mem inuse %lu",
		      (unsigned long)isc_mem_inuse(cleaner->acache->mctx));

	LOCK(&acache->lock);

	head = ISC_LIST_HEAD(acache->entries);
	if (head != NULL)
		dns_acache_attachentry(head, &cleaner->current_entry);

	UNLOCK(&acache->lock);

	if (cleaner->current_entry != NULL) {
		cleaner->ncleaned = 0;
		cleaner->state = cleaner_s_busy;
		isc_task_send(acache->task, &cleaner->resched_event);
	}

	return;
}

static void
end_cleaning(acache_cleaner_t *cleaner, isc_event_t *event) {
	dns_acache_t *acache = cleaner->acache;

	REQUIRE(CLEANER_BUSY(cleaner));
	REQUIRE(event != NULL);
	REQUIRE(DNS_ACACHEENTRY_VALID(cleaner->current_entry));

	/* No need to lock the cleaner (see begin_cleaning()). */

	LOCK(&acache->lock);

	/*
	 * Even if the cleaner has the last reference to the entry, which means
	 * the entry has been unused, it may still be linked if unlinking the
	 * entry has been delayed due to the reference.
	 */
	if (isc_refcount_current(&cleaner->current_entry->references) == 1) {
		INSIST(cleaner->current_entry->callback == NULL);
		
		if (ISC_LINK_LINKED(cleaner->current_entry, link)) {
			ISC_LIST_UNLINK(acache->entries,
					cleaner->current_entry, link);
		}
	}
	dns_acache_detachentry(&cleaner->current_entry);

	if (cleaner->overmem)
		acache->stats.overmem++;
	acache->stats.cleaned += cleaner->ncleaned;
	acache->stats.cleaner_runs++;

	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_ACACHE,
		      ISC_LOG_NOTICE,
		      "acache %p stats: hits=%d misses=%d queries=%d "
		      "adds=%d deleted=%d "
		      "cleaned=%d cleaner_runs=%d overmem=%d "
		      "overmem_nocreates=%d nomem=%d",
		      acache,
		      acache->stats.hits, acache->stats.misses,
		      acache->stats.queries,
		      acache->stats.adds, acache->stats.deleted,
		      acache->stats.cleaned, acache->stats.cleaner_runs,
		      acache->stats.overmem, acache->stats.overmem_nocreates, 
		      acache->stats.nomem);
	reset_stats(acache);

	isc_stdtime_get(&cleaner->last_cleanup_time);

	UNLOCK(&acache->lock);

	dns_acache_setcleaninginterval(cleaner->acache,
				       cleaner->cleaning_interval);

	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_ACACHE,
		      ISC_LOG_DEBUG(1), "end acache cleaning, "
		      "%lu entries cleaned, mem inuse %lu",
		      cleaner->ncleaned,
		      (unsigned long)isc_mem_inuse(cleaner->acache->mctx));

	if (cleaner->overmem) {
		isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
			      DNS_LOGMODULE_ACACHE, ISC_LOG_NOTICE,
			      "acache is still in overmem state "
			      "after cleaning");
	}

	cleaner->ncleaned = 0;
	cleaner->state = cleaner_s_idle;
	cleaner->resched_event = event;
}

/*
 * This is run once for every acache-cleaning-interval as defined
 * in named.conf.
 */
static void
acache_cleaning_timer_action(isc_task_t *task, isc_event_t *event) {
	acache_cleaner_t *cleaner = event->ev_arg;

	UNUSED(task);

	INSIST(event->ev_type == ISC_TIMEREVENT_TICK);

	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_ACACHE,
		      ISC_LOG_DEBUG(1), "acache cleaning timer fired, "
		      "cleaner state = %d", cleaner->state);

	if (cleaner->state == cleaner_s_idle)
		begin_cleaning(cleaner);

	isc_event_free(&event);
}

/* The caller must hold entry lock. */
static inline isc_boolean_t
entry_stale(acache_cleaner_t *cleaner, dns_acacheentry_t *entry,
	    isc_stdtime32_t now32, unsigned int interval)
{
	/*
	 * If the callback has been canceled, we definitely do not need the
	 * entry.
	 */
	if (entry->callback == NULL)
		return (ISC_TRUE);

	if (interval > cleaner->cleaning_interval)
		interval = cleaner->cleaning_interval;

	if (entry->lastused + interval < now32)
		return (ISC_TRUE);

	/*
	 * If the acache is in the overmem state, probabilistically decide if
	 * the entry should be purged, based on the time passed from its last
	 * use and the cleaning interval.
	 */
	if (cleaner->overmem) {
		unsigned int passed =
			now32 - entry->lastused; /* <= interval */
		isc_uint32_t val;

		if (passed > interval / 2)
			return (ISC_TRUE);
		isc_random_get(&val);
		if (passed > interval / 4)
			return (ISC_TF(val % 4 == 0));
		return (ISC_TF(val % 8 == 0));
	}

	return (ISC_FALSE);
}

/*
 * Do incremental cleaning.
 */
static void
acache_incremental_cleaning_action(isc_task_t *task, isc_event_t *event) {
	acache_cleaner_t *cleaner = event->ev_arg;
	dns_acache_t *acache = cleaner->acache;
	dns_acacheentry_t *entry, *next = NULL;
	int n_entries;
	isc_stdtime32_t now32, last32;
	isc_stdtime_t now;
	unsigned int interval;

	INSIST(DNS_ACACHE_VALID(acache));
	INSIST(task == acache->task);
	INSIST(event->ev_type == DNS_EVENT_ACACHECLEAN);

	if (cleaner->state == cleaner_s_done) {
		cleaner->state = cleaner_s_busy;
		end_cleaning(cleaner, event);
		return;
	}

	INSIST(CLEANER_BUSY(cleaner));

	n_entries = cleaner->increment;

	isc_stdtime_get(&now);
	isc_stdtime_convert32(now, &now32);

	LOCK(&acache->lock);

	entry = cleaner->current_entry;
	isc_stdtime_convert32(cleaner->last_cleanup_time, &last32);
	INSIST(now32 > last32);
	interval = now32 - last32;

	while (n_entries-- > 0) {
		isc_boolean_t is_stale = ISC_FALSE;

		INSIST(entry != NULL);

		next = ISC_LIST_NEXT(entry, link);

		ACACHE_LOCK(&acache->entrylocks[entry->locknum],
			    isc_rwlocktype_write);

		is_stale = entry_stale(cleaner, entry, now32, interval);
		if (is_stale) {
			ISC_LIST_UNLINK(acache->entries, entry, link);
			unlink_dbentries(acache, entry);
			if (entry->callback != NULL)
				(entry->callback)(entry, &entry->cbarg);
			entry->callback = NULL;

			cleaner->ncleaned++;
		}

		ACACHE_UNLOCK(&acache->entrylocks[entry->locknum],
			      isc_rwlocktype_write);

		if (is_stale)
			dns_acache_detachentry(&entry);

		if (next == NULL) {
			if (cleaner->overmem) {
				entry = ISC_LIST_HEAD(acache->entries);
				if (entry != NULL) {
					/*
					 * If we are still in the overmem
					 * state, keep cleaning.
					 */
					isc_log_write(dns_lctx,
						      DNS_LOGCATEGORY_DATABASE,
						      DNS_LOGMODULE_ACACHE,
						      ISC_LOG_DEBUG(1),
						      "acache cleaner: "
						      "still overmem, "
						      "reset and try again");
					continue;
				}
			}

			UNLOCK(&acache->lock);
			end_cleaning(cleaner, event);
			return;
		}

		entry = next;
	}

	/*
	 * We have successfully performed a cleaning increment but have
	 * not gone through the entire cache.  Remember the entry that will
	 * be the starting point in the next clean-up, and reschedule another
	 * batch.  If it fails, just try to continue anyway.
	 */