mark some expensive parts of invariant checks as expensive and disabled by default. introduce undead_peers to destruct all peer_connections in the network thread. they hang around while waiting for all outstanding disk jobs to complete. make the asio-debugging output a bit prettier

include/libtorrent/aux_/session_impl.hpp

@@ -748,6 +748,14 @@ namespace libtorrent
 			// they would linger and stall or hang session shutdown
 			std::set<boost::shared_ptr<socket_type> > m_incoming_sockets;
 			
+			// peer connections are put here when disconnected to avoid
+			// race conditions with the disk thread. It's important that
+			// peer connections are destructed from the network thread,
+			// once a peer is disconnected, it's put in this list and
+			// every second their refcount is checked, and if it's 1,
+			// they are deleted (from the network thread)
+			std::vector<boost::intrusive_ptr<peer_connection> > m_undead_peers;
+
 			// filters incoming connections
 			ip_filter m_ip_filter;
 

src/peer_connection.cpp

@@ -5883,6 +5883,7 @@ namespace libtorrent
 				TORRENT_ASSERT(m_upload_only);
 		}
 
+#ifdef TORRENT_EXPENSIVE_INVARIANT_CHECKS
 		if (t->has_picker())
 		{
 			std::map<piece_block, peer_count_t> num_requests;
@@ -5926,7 +5927,7 @@ namespace libtorrent
 					TORRENT_ASSERT(picker_count == count);
 			}
 		}
-#ifdef TORRENT_EXPENSIVE_INVARIANT_CHECKS
+
 		if (m_peer_info && type() == bittorrent_connection)
 		{
 			policy::const_iterator i = t->get_policy().begin_peer();

src/session_impl.cpp

@@ -1746,6 +1746,8 @@ namespace aux {
 		m_udp_socket.close();
 		m_external_udp_port = 0;
 
+		m_undead_peers.clear();
+
 #ifndef TORRENT_DISABLE_GEO_IP
 		if (m_asnum_db) GeoIP_delete(m_asnum_db);
 		if (m_country_db) GeoIP_delete(m_country_db);
@@ -2898,6 +2900,12 @@ retry:
 	{
 		TORRENT_ASSERT(is_network_thread());
 
+		// someone else is holding a reference, it's important that
+		// it's destructed from the network thread. Make sure the
+		// last reference is held by the network thread.
+		if (!p->refcount() == 1)
+			m_undead_peers.push_back((peer_connection*)p);
+
 // too expensive
 //		INVARIANT_CHECK;
 
@@ -3082,6 +3090,12 @@ retry:
 			update_dht_announce_interval();
 #endif
 
+		// remove undead peers that only have this list as their reference keeping them alive
+		std::vector<boost::intrusive_ptr<peer_connection> >::iterator i = std::remove_if(
+			m_undead_peers.begin(), m_undead_peers.end()
+			, boost::bind(&peer_connection::refcount, _1) == 1);
+		m_undead_peers.erase(i, m_undead_peers.end());
+
 		int tick_interval_ms = total_milliseconds(now - m_last_second_tick);
 		m_last_second_tick = now;
 		m_tick_residual += tick_interval_ms - 1000;
@@ -5828,7 +5842,7 @@ retry:
 		{
 			sleep(1000);
 			++counter;
-			printf("\n==== Waiting to shut down: %d ==== conn-queue: %d connecting: %d timeout (next: %f max: %f)\n\n"
+			printf("\x1b[2J\x1b[0;0H\x1b[33m==== Waiting to shut down: %d ==== conn-queue: %d connecting: %d timeout (next: %f max: %f)\x1b[0m\n\n"
 				, counter, m_half_open.size(), m_half_open.num_connecting(), m_half_open.next_timeout()
 				, m_half_open.max_timeout());
 		}

src/torrent.cpp

@@ -6579,6 +6579,7 @@ namespace libtorrent
 		else
 			TORRENT_ASSERT(m_queued_for_checking);
 
+#ifdef TORRENT_EXPENSIVE_INVARIANT_CHECKS
 		if (!m_ses.m_queued_for_checking.empty())
 		{
 			// if there are torrents waiting to be checked
@@ -6609,6 +6610,7 @@ namespace libtorrent
 				TORRENT_ASSERT(found >= 1);
 			}
 		}
+#endif
 
 		TORRENT_ASSERT(m_resume_entry.type() == lazy_entry::dict_t
 			|| m_resume_entry.type() == lazy_entry::none_t);