acache.c

非常好的dns解析软件

	INSIST(next != NULL && next != cleaner->current_entry);
	dns_acache_detachentry(&cleaner->current_entry);
	dns_acache_attachentry(next, &cleaner->current_entry);

	UNLOCK(&acache->lock);

	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_ACACHE,
		      ISC_LOG_DEBUG(1), "acache cleaner: checked %d entries, "
		      "mem inuse %lu, sleeping", cleaner->increment,
		      (unsigned long)isc_mem_inuse(cleaner->acache->mctx));

	isc_task_send(task, &event);
	INSIST(CLEANER_BUSY(cleaner));

	return;
}

/*
 * This is called when the acache either surpasses its upper limit
 * or shrinks beyond its lower limit.
 */
static void
acache_overmem_cleaning_action(isc_task_t *task, isc_event_t *event) {
	acache_cleaner_t *cleaner = event->ev_arg;
	isc_boolean_t want_cleaning = ISC_FALSE;
	
	UNUSED(task);

	INSIST(event->ev_type == DNS_EVENT_ACACHEOVERMEM);
	INSIST(cleaner->overmem_event == NULL);

	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE, DNS_LOGMODULE_ACACHE,
		      ISC_LOG_DEBUG(1), "overmem_cleaning_action called, "
		      "overmem = %d, state = %d", cleaner->overmem,
		      cleaner->state);

	LOCK(&cleaner->lock);

	if (cleaner->overmem) {
		if (cleaner->state == cleaner_s_idle)
			want_cleaning = ISC_TRUE;
	} else {
		if (cleaner->state == cleaner_s_busy)
			/*
			 * end_cleaning() can't be called here because
			 * then both cleaner->overmem_event and
			 * cleaner->resched_event will point to this
			 * event.  Set the state to done, and then
			 * when the acache_incremental_cleaning_action() event
			 * is posted, it will handle the end_cleaning.
			 */
			cleaner->state = cleaner_s_done;
	}

	cleaner->overmem_event = event;

	UNLOCK(&cleaner->lock);

	if (want_cleaning)
		begin_cleaning(cleaner);
}

static void
water(void *arg, int mark) {
	dns_acache_t *acache = arg;
	isc_boolean_t overmem = ISC_TF(mark == ISC_MEM_HIWATER);

	REQUIRE(DNS_ACACHE_VALID(acache));

	isc_log_write(dns_lctx, DNS_LOGCATEGORY_DATABASE,
		      DNS_LOGMODULE_ACACHE, ISC_LOG_DEBUG(1),
		      "acache memory reaches %s watermark, mem inuse %lu",
		      overmem ? "high" : "low",
		      (unsigned long)isc_mem_inuse(acache->mctx));

	LOCK(&acache->cleaner.lock);

	acache->cleaner.overmem = overmem;

	if (acache->cleaner.overmem_event != NULL)
		isc_task_send(acache->task, &acache->cleaner.overmem_event);

	UNLOCK(&acache->cleaner.lock);
}

/*
 * The cleaner task is shutting down; do the necessary cleanup.
 */
static void
acache_cleaner_shutdown_action(isc_task_t *task, isc_event_t *event) {
	dns_acache_t *acache = event->ev_arg;
	isc_boolean_t should_free = ISC_FALSE;

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

	ATRACE("acache cleaner shutdown");

	if (CLEANER_BUSY(&acache->cleaner))
		end_cleaning(&acache->cleaner, event);
	else
		isc_event_free(&event);

	LOCK(&acache->lock);

	acache->live_cleaners--;
	INSIST(acache->live_cleaners == 0);

	if (isc_refcount_current(&acache->refs) == 0) {
		INSIST(check_noentry(acache) == ISC_TRUE);
		should_free = ISC_TRUE;
	}

	/*
	 * By detaching the timer in the context of its task,
	 * we are guaranteed that there will be no further timer
	 * events.
	 */
	if (acache->cleaner.cleaning_timer != NULL)
		isc_timer_detach(&acache->cleaner.cleaning_timer);

	/* Make sure we don't reschedule anymore. */
	(void)isc_task_purge(task, NULL, DNS_EVENT_ACACHECLEAN, NULL);

	UNLOCK(&acache->lock);

	if (should_free)
		destroy(acache);
}

/*
 *	Public functions.
 */

isc_result_t
dns_acache_create(dns_acache_t **acachep, isc_mem_t *mctx,
		  isc_taskmgr_t *taskmgr, isc_timermgr_t *timermgr)
{
	int i;
	isc_result_t result;
	dns_acache_t *acache;

	REQUIRE(acachep != NULL && *acachep == NULL);
	REQUIRE(mctx != NULL);
	REQUIRE(taskmgr != NULL);

	acache = isc_mem_get(mctx, sizeof(*acache));
	if (acache == NULL)
		return (ISC_R_NOMEMORY);

	ATRACE("create");

	result = isc_refcount_init(&acache->refs, 1);
	if (result != ISC_R_SUCCESS) {
		isc_mem_put(mctx, acache, sizeof(*acache));
		return (result);
	}

	result = isc_mutex_init(&acache->lock);
	if (result != ISC_R_SUCCESS) {
		isc_refcount_decrement(&acache->refs, NULL);
		isc_refcount_destroy(&acache->refs);
		isc_mem_put(mctx, acache, sizeof(*acache));
		return (result);
	}

	acache->mctx = NULL;
	isc_mem_attach(mctx, &acache->mctx);
	ISC_LIST_INIT(acache->entries);

	acache->shutting_down = ISC_FALSE;

	acache->task = NULL;
	acache->entrylocks = NULL;

	result = isc_task_create(taskmgr, 1, &acache->task);
	if (result != ISC_R_SUCCESS) {
		UNEXPECTED_ERROR(__FILE__, __LINE__,
				 "isc_task_create() failed(): %s",
				 dns_result_totext(result));
		result = ISC_R_UNEXPECTED;
		goto cleanup;
	}
	isc_task_setname(acache->task, "acachetask", acache);
	ISC_EVENT_INIT(&acache->cevent, sizeof(acache->cevent), 0, NULL,
		       DNS_EVENT_ACACHECONTROL, shutdown_task, NULL,
		       NULL, NULL, NULL);
	acache->cevent_sent = ISC_FALSE;

	acache->dbentries = 0;
	for (i = 0; i < DBBUCKETS; i++)
		ISC_LIST_INIT(acache->dbbucket[i]);

	acache->entrylocks = isc_mem_get(mctx, sizeof(*acache->entrylocks) *
					 DEFAULT_ACACHE_ENTRY_LOCK_COUNT);
	if (acache->entrylocks == NULL) {
		result = ISC_R_NOMEMORY;
		goto cleanup;
	}
	for (i = 0; i < DEFAULT_ACACHE_ENTRY_LOCK_COUNT; i++) {
		result = ACACHE_INITLOCK(&acache->entrylocks[i]);
		if (result != ISC_R_SUCCESS) {
			while (i-- > 0)
				ACACHE_DESTROYLOCK(&acache->entrylocks[i]);
			isc_mem_put(mctx, acache->entrylocks,
				    sizeof(*acache->entrylocks) *
				    DEFAULT_ACACHE_ENTRY_LOCK_COUNT);
			acache->entrylocks = NULL;
			goto cleanup;
		}
	}

	acache->live_cleaners = 0;
	result = acache_cleaner_init(acache, timermgr, &acache->cleaner); 
	if (result != ISC_R_SUCCESS)
		goto cleanup;

	acache->stats.cleaner_runs = 0;
	reset_stats(acache);

	acache->magic = ACACHE_MAGIC;

	*acachep = acache;
	return (ISC_R_SUCCESS);

 cleanup:
	if (acache->task != NULL)
		isc_task_detach(&acache->task);
	DESTROYLOCK(&acache->lock);
	isc_refcount_decrement(&acache->refs, NULL);
	isc_refcount_destroy(&acache->refs);
	if (acache->entrylocks != NULL) {
		for (i = 0; i < DEFAULT_ACACHE_ENTRY_LOCK_COUNT; i++)
			ACACHE_DESTROYLOCK(&acache->entrylocks[i]);
		isc_mem_put(mctx, acache->entrylocks,
			    sizeof(*acache->entrylocks) *
			    DEFAULT_ACACHE_ENTRY_LOCK_COUNT);
	}
	isc_mem_put(mctx, acache, sizeof(*acache));
	isc_mem_detach(&mctx);

	return (result);
}

void
dns_acache_attach(dns_acache_t *source, dns_acache_t **targetp) {
	REQUIRE(DNS_ACACHE_VALID(source));
	REQUIRE(targetp != NULL && *targetp == NULL);

	AATRACE(source, "attach");

	isc_refcount_increment(&source->refs, NULL);

	*targetp = source;
}

void
dns_acache_countquerymiss(dns_acache_t *acache) {
	acache->stats.misses++; 	/* XXXSK danger: unlocked! */
	acache->stats.queries++;	/* XXXSK danger: unlocked! */
}

void
dns_acache_detach(dns_acache_t **acachep) {
	dns_acache_t *acache;
	unsigned int refs;
	isc_boolean_t should_free = ISC_FALSE;

	REQUIRE(acachep != NULL && DNS_ACACHE_VALID(*acachep));
	acache = *acachep;

	ATRACE("detach");

	isc_refcount_decrement(&acache->refs, &refs);
	if (refs == 0) {
		INSIST(check_noentry(acache) == ISC_TRUE);
		should_free = ISC_TRUE;
	}

	*acachep = NULL;

	/*
	 * If we're exiting and the cleaner task exists, let it free the cache.
	 */
	if (should_free && acache->live_cleaners > 0) {
		isc_task_shutdown(acache->task);
		should_free = ISC_FALSE;
	}
	
	if (should_free)
		destroy(acache);
}

void
dns_acache_shutdown(dns_acache_t *acache) {
	REQUIRE(DNS_ACACHE_VALID(acache));

	LOCK(&acache->lock);

	ATRACE("shutdown");

	if (!acache->shutting_down) {
		isc_event_t *event;
		dns_acache_t *acache_evarg = NULL;

		INSIST(!acache->cevent_sent);

		acache->shutting_down = ISC_TRUE;

		isc_mem_setwater(acache->mctx, NULL, NULL, 0, 0);

		/*
		 * Self attach the object in order to prevent it from being
		 * destroyed while waiting for the event.
		 */
		dns_acache_attach(acache, &acache_evarg);
		event = &acache->cevent;
		event->ev_arg = acache_evarg;
		isc_task_send(acache->task, &event);
		acache->cevent_sent = ISC_TRUE;
	}

	UNLOCK(&acache->lock);
}

isc_result_t
dns_acache_setdb(dns_acache_t *acache, dns_db_t *db) {
	int bucket;
	dbentry_t *dbentry;
	isc_result_t result = ISC_R_SUCCESS;

	REQUIRE(DNS_ACACHE_VALID(acache));
	REQUIRE(db != NULL);

	ATRACE("setdb");

	LOCK(&acache->lock);

	dbentry = NULL;
	result = finddbent(acache, db, &dbentry);
	if (result == ISC_R_SUCCESS) {
		result = ISC_R_EXISTS;
		goto end;
	}
	result = ISC_R_SUCCESS;

	dbentry = isc_mem_get(acache->mctx, sizeof(*dbentry));
	if (dbentry == NULL) {
		result = ISC_R_NOMEMORY;
		goto end;
	}

	ISC_LINK_INIT(dbentry, link);
	ISC_LIST_INIT(dbentry->originlist);
	ISC_LIST_INIT(dbentry->referlist);

	dbentry->db = NULL;
	dns_db_attach(db, &dbentry->db);

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

	ISC_LIST_APPEND(acache->dbbucket[bucket], dbentry, link);

	acache->dbentries++;

 end:
	UNLOCK(&acache->lock);

	return (result);
}

isc_result_t
dns_acache_putdb(dns_acache_t *acache, dns_db_t *db) {
	int bucket;
	isc_result_t result;
	dbentry_t *dbentry;
	dns_acacheentry_t *entry;

	REQUIRE(DNS_ACACHE_VALID(acache));
	REQUIRE(db != NULL);

	ATRACE("putdb");

	LOCK(&acache->lock);

	dbentry = NULL;
	result = finddbent(acache, db, &dbentry);
	if (result != ISC_R_SUCCESS) {
		/*
		 * The entry may have not been created due to memory shortage.
		 */
		UNLOCK(&acache->lock);
		return (ISC_R_NOTFOUND);
	}

	/*
	 * Release corresponding cache entries: for each entry, release all
	 * links the entry has, and then callback to the entry holder (if any).
	 * If no other external references exist (this can happen if the
	 * original holder has canceled callback,) destroy it here.
	 */
	while ((entry = ISC_LIST_HEAD(dbentry->originlist)) != NULL) {
		ACACHE_LOCK(&acache->entrylocks[entry->locknum],
			    isc_rwlocktype_write);

		/*
		 * Releasing olink first would avoid finddbent() in
		 * unlink_dbentries().
		 */
		ISC_LIST_UNLINK(dbentry->originlist, entry, olink);
		if (acache->cleaner.current_entry != entry)
			ISC_LIST_UNLINK(acache->entries, entry, link);
		unlink_dbentries(acache, entry);

		if (entry->callback != NULL)
			(entry->callback)(entry, &entry->cbarg);
		entry->callback = NULL;

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

		if (acache->cleaner.current_entry != entry)
			dns_acache_detachentry(&entry);
	}
	while ((entry = ISC_LIST_HEAD(dbentry->referlist)) != NULL) {
		ACACHE_LOCK(&acache->entrylocks[entry->locknum],
			    isc_rwlocktype_write);

		ISC_LIST_UNLINK(dbentry->referlist, entry, rlink);
		if (acache->cleaner.current_entry != entry)
			ISC_LIST_UNLINK(acache->entries, entry, link);
		unlink_dbentries(acache, entry);

		if (entry->callback != NULL)
			(entry->callback)(entry, &entry->cbarg);
		entry->callback = NULL;

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

		if (acache->cleaner.current_entry != entry)
			dns_acache_detachentry(&entry);
	}