diff --git a/include/libtorrent/debug.hpp b/include/libtorrent/debug.hpp
index 87d65b4d8..19d196e90 100755
--- a/include/libtorrent/debug.hpp
+++ b/include/libtorrent/debug.hpp
@@ -48,9 +48,20 @@ POSSIBILITY OF SUCH DAMAGE.
 #pragma warning(pop)
 #endif
 
+
 namespace libtorrent
 {
 
+	// PROFILING CODE
+#ifdef TORRENT_PROFILE
+
+	void add_checkpoint(std::string const& str);
+	void print_checkpoints();
+#define TORRENT_CHECKPOINT(str) libtorrent::add_checkpoint(str)
+#else
+#define TORRENT_CHECKPOINT(str) void(0)
+#endif
+
 	// DEBUG API
 
 	struct logger
diff --git a/include/libtorrent/torrent.hpp b/include/libtorrent/torrent.hpp
index 2e7c5a37c..ac061242b 100755
--- a/include/libtorrent/torrent.hpp
+++ b/include/libtorrent/torrent.hpp
@@ -98,6 +98,7 @@ namespace libtorrent
 			detail::session_impl& ses
 			, detail::checker_impl& checker
 			, entry const& metadata
+			, torrent_info const& tf
 			, boost::filesystem::path const& save_path
 			, address const& net_interface
 			, bool compact_mode
diff --git a/src/session.cpp b/src/session.cpp
index 5a4cc320c..cd2ab26fc 100755
--- a/src/session.cpp
+++ b/src/session.cpp
@@ -1133,6 +1133,7 @@ namespace libtorrent
 		, bool compact_mode
 		, int block_size)
 	{
+		TORRENT_CHECKPOINT("++ session::add_torrent()");
 		// make sure the block_size is an even power of 2
 #ifndef NDEBUG
 		for (int i = 0; i < 32; ++i)
@@ -1152,17 +1153,13 @@ namespace libtorrent
 		if (ti.begin_files() == ti.end_files())
 			throw std::runtime_error("no files in torrent");
 
-		{
-			// lock the session
-			boost::mutex::scoped_lock l(m_impl.m_mutex);
+		// lock the session and the checker thread (the order is important!)
+		boost::mutex::scoped_lock l(m_impl.m_mutex);
+		boost::mutex::scoped_lock l2(m_checker_impl.m_mutex);
 
-			// is the torrent already active?
-			if (m_impl.find_torrent(ti.info_hash()))
-				throw duplicate_torrent();
-		}
-
-		// lock the checker_thread
-		boost::mutex::scoped_lock l(m_checker_impl.m_mutex);
+		// is the torrent already active?
+		if (m_impl.find_torrent(ti.info_hash()))
+			throw duplicate_torrent();
 
 		// is the torrent currently being checked?
 		if (m_checker_impl.find_torrent(ti.info_hash()))
@@ -1172,7 +1169,7 @@ namespace libtorrent
 		// the checker thread and store it before starting
 		// the thread
 		boost::shared_ptr<torrent> torrent_ptr(
-			new torrent(m_impl, m_checker_impl, metadata, save_path
+			new torrent(m_impl, m_checker_impl, metadata, ti, save_path
 				, m_impl.m_listen_interface, compact_mode, block_size));
 
 		boost::shared_ptr<detail::piece_checker_data> d(
@@ -1188,6 +1185,7 @@ namespace libtorrent
 		// job in its queue
 		m_checker_impl.m_cond.notify_one();
 
+		TORRENT_CHECKPOINT("-- session::add_torrent()");
 		return torrent_handle(&m_impl, &m_checker_impl, ti.info_hash());
 	}