Improved bug-957 fix for 0.2.2.

Really, our idiocy was that we were calling event_set() on the same
event more than once, which sometimes led to us calling event_set() on
an event that was already inserted, thus making it look uninserted.
With this patch, we just initialize the timeout events when we create
the requests and nameservers, and we don't need to worry about
double-add and double-del cases at all.

src/or/eventdns.c

@@ -173,8 +173,6 @@ struct evdns_request {
 	/* these objects are kept in a circular list */
 	struct evdns_request *next, *prev;
 
-	u16 timeout_event_deleted; /**< Debugging: where was timeout_event
-								* deleted?  0 for "it's added." */
 	struct event timeout_event;
 
 	u16 trans_id;  /* the transaction id */
@@ -214,8 +212,6 @@ struct nameserver {
 	struct event event;
 	/* these objects are kept in a circular list */
 	struct nameserver *next, *prev;
-	u16 timeout_event_deleted; /**< Debugging: where was timeout_event
-								* deleted?  0 for "it's added." */
 	struct event timeout_event; /* used to keep the timeout for */
 								/* when we next probe this server. */
 								/* Valid if state == 0 */
@@ -474,51 +470,10 @@ sockaddr_eq(const struct sockaddr *sa1, const struct sockaddr *sa2,
 	return 1;
 }
 
-/* for debugging bug 929.  XXXX022 */
+#define add_timeout_event(s, to)				\
-static int
+	(event_add(&(s)->timeout_event, (to)))
-_add_timeout_event(u16 *lineno, struct event *ev, struct timeval *to)
+#define del_timeout_event(s)					\
-{
+	(event_del(&(s)->timeout_event))
-	*lineno = 0;
-	return evtimer_add(ev, to);
-}
-#define add_timeout_event(s, to) \
-	(_add_timeout_event(&(s)->timeout_event_deleted, &(s)->timeout_event, (to)))
-
-/* for debugging bug 929.  XXXX022 */
-static int
-_del_timeout_event(u16 *lineno, struct event *ev, int line)
-{
-	if (*lineno) {
-		log(EVDNS_LOG_DEBUG,
-			"Duplicate timeout event_del from line %d: first call "
-			"was at %d.", line, (int)*lineno);
-		return 0;
-	} else {
-		*lineno = (u16)line;
-		return event_del(ev);
-	}
-}
-#define del_timeout_event(s)											\
-	(_del_timeout_event(&(s)->timeout_event_deleted, &(s)->timeout_event, \
-						__LINE__))
-/* For debugging bug 929/957. XXXX022 */
-static int
-_del_timeout_event_if_set(u16 *lineno, struct event *ev, int line)
-{
-	if (*lineno == 0) {
-		log(EVDNS_LOG_DEBUG,
-			"Event that I thought was non-added as of line %d "
-			"was actually added on line %d",
-			line, (int)*lineno);
-		*lineno = line;
-		return event_del(ev);
-	}
-	return 0;
-}
-#define del_timeout_event_if_set(s)				\
-	_del_timeout_event_if_set(&(s)->timeout_event_deleted,	\
-							  &(s)->timeout_event,			\
-							  __LINE__)
 
 /* This walks the list of inflight requests to find the */
 /* one with a matching transaction id. Returns NULL on */
@@ -555,7 +510,7 @@ static void
 nameserver_probe_failed(struct nameserver *const ns) {
 	const struct timeval * timeout;
 	del_timeout_event(ns);
-	CLEAR(&ns->timeout_event);
+
 	if (ns->state == 1) {
 		/* This can happen if the nameserver acts in a way which makes us mark */
 		/* it as bad and then starts sending good replies. */
@@ -567,8 +522,6 @@ nameserver_probe_failed(struct nameserver *const ns) {
 										global_nameserver_timeouts_length - 1)];
 	ns->failed_times++;
 
-	del_timeout_event_if_set(ns);
-	evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns);
 	if (add_timeout_event(ns, (struct timeval *) timeout) < 0) {
 		log(EVDNS_LOG_WARN,
 			"Error from libevent when adding timer event for %s",
@@ -597,8 +550,6 @@ nameserver_failed(struct nameserver *const ns, const char *msg) {
 	ns->state = 0;
 	ns->failed_times = 1;
 
-	del_timeout_event_if_set(ns);
-	evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns);
 	if (add_timeout_event(ns, (struct timeval *) &global_nameserver_timeouts[0]) < 0) {
 		log(EVDNS_LOG_WARN,
 			"Error from libevent when adding timer event for %s",
@@ -634,7 +585,6 @@ nameserver_up(struct nameserver *const ns) {
 	log(EVDNS_LOG_WARN, "Nameserver %s is back up",
 		debug_ntop((struct sockaddr *)&ns->address));
 	del_timeout_event(ns);
-	CLEAR(&ns->timeout_event);
 	ns->state = 1;
 	ns->failed_times = 0;
 	ns->timedout = 0;
@@ -666,7 +616,6 @@ request_finished(struct evdns_request *const req, struct evdns_request **head) {
 	log(EVDNS_LOG_DEBUG, "Removing timeout for request %lx",
 		(unsigned long) req);
 	del_timeout_event(req);
-	CLEAR(&req->timeout_event);
 
 	search_request_finished(req);
 	global_requests_inflight--;
@@ -2046,7 +1995,6 @@ evdns_request_timeout_callback(int fd, short events, void *arg) {
 		 * request_finished; that one already deletes the timeout event.
 		 * XXXX021 port this change to libevent. */
 		del_timeout_event(req);
-		CLEAR(&req->timeout_event);
 		evdns_request_transmit(req);
 	}
 }
@@ -2109,8 +2057,7 @@ evdns_request_transmit(struct evdns_request *req) {
 		/* transmitted; we need to check for timeout. */
 		log(EVDNS_LOG_DEBUG,
 			"Setting timeout for request %lx", (unsigned long) req);
-		del_timeout_event_if_set(req);
+
-		evtimer_set(&req->timeout_event, evdns_request_timeout_callback, req);
 		if (add_timeout_event(req, &global_timeout) < 0) {
 			log(EVDNS_LOG_WARN,
 				"Error from libevent when adding timer for request %lx",
@@ -2225,7 +2172,6 @@ evdns_clear_nameservers_and_suspend(void)
 		(void) event_del(&server->event);
 		CLEAR(&server->event);
 		del_timeout_event(server);
-		CLEAR(&server->timeout_event);
 		if (server->socket >= 0)
 			CLOSE_SOCKET(server->socket);
 		CLEAR(server);
@@ -2243,7 +2189,6 @@ evdns_clear_nameservers_and_suspend(void)
 		req->ns = NULL;
 		/* ???? What to do about searches? */
 		del_timeout_event(req);
-		CLEAR(&req->timeout_event);
 		req->trans_id = 0;
 		req->transmit_me = 0;
 
@@ -2318,7 +2263,8 @@ _evdns_nameserver_add_impl(const struct sockaddr *address,
 	if (!ns) return -1;
 
 	memset(ns, 0, sizeof(struct nameserver));
-	ns->timeout_event_deleted = __LINE__;
+
+	evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns);
 
 	ns->socket = socket(PF_INET, SOCK_DGRAM, 0);
 	if (ns->socket < 0) { err = 1; goto out1; }
@@ -2553,7 +2499,8 @@ request_new(int type, const char *name, int flags,
 	}
 
 	memset(req, 0, sizeof(struct evdns_request));
-	req->timeout_event_deleted = __LINE__;
+
+	evtimer_set(&req->timeout_event, evdns_request_timeout_callback, req);
 
 	if (global_randomize_case) {
 		unsigned i;
@@ -3384,8 +3331,7 @@ evdns_shutdown(int fail_requests)
 		if (server->socket >= 0)
 			CLOSE_SOCKET(server->socket);
 		(void) event_del(&server->event);
-		if (server->state == 0)
+		del_timeout_event(server);
-			del_timeout_event(server);
 		CLEAR(server);
 		mm_free(server);
 		if (server_next == server_head)