massive changes to clean up what happens during session destruction when an exception is thrown

git-svn-id: svn://localhost/ardour2/trunk@1261 d708f5d6-7413-0410-9779-e7cbd77b26cf

13 files changed, 227 insertions, 144 deletions

diff --git a/gtk2_ardour/ardour_ui.cc b/gtk2_ardour/ardour_ui.cc
index 4875b8db89..9692c89218 100644
--- a/gtk2_ardour/ardour_ui.cc
+++ b/gtk2_ardour/ardour_ui.cc
@@ -1262,14 +1262,6 @@ ARDOUR_UI::do_engine_start ()
 		engine->start();
 	}
 
-	catch (AudioEngine::PortRegistrationFailure& err) {
-		engine->stop ();
-		error << _("Unable to create all required ports")
-		      << endmsg;
-		unload_session ();
-		return -1;
-	}
-
 	catch (...) {
 		engine->stop ();
 		error << _("Unable to start the session running")
@@ -1588,7 +1580,7 @@ ARDOUR_UI::save_template ()
 }
 
 void
-ARDOUR_UI::new_session (bool startup, std::string predetermined_path)
+ARDOUR_UI::new_session (std::string predetermined_path)
 {
 	string session_name;
 	string session_path;
@@ -1818,6 +1810,14 @@ This prevents the session from being loaded."));
 		new_session = new Session (*engine, path, snap_name, mix_template);
 	}
 
+	/* handle this one in a different way than all others, so that its clear what happened */
+	
+	catch (AudioEngine::PortRegistrationFailure& err) {
+		error << _("Unable to create all required ports")
+		      << endmsg;
+		return -1;
+	}
+
 	catch (...) {
 
 		error << string_compose(_("Session \"%1 (snapshot %2)\" did not load successfully"), path, snap_name) << endmsg;
@@ -2330,7 +2330,7 @@ ARDOUR_UI::cmdline_new_session (string path)
 		path = str;
 	}
 
-	new_session (false, path);
+	new_session (path);
 
 	_will_create_new_session_automatically = false; /* done it */
 	return FALSE; /* don't call it again */
diff --git a/gtk2_ardour/ardour_ui.h b/gtk2_ardour/ardour_ui.h
index fb8d87f05d..77418f9ab6 100644
--- a/gtk2_ardour/ardour_ui.h
+++ b/gtk2_ardour/ardour_ui.h
@@ -128,7 +128,7 @@ class ARDOUR_UI : public Gtkmm2ext::UI
 		_will_create_new_session_automatically = yn;
 	}
 
-        void new_session(bool startup = false, std::string path = string());
+        void new_session(std::string path = string());
 	gint cmdline_new_session (string path);
 	int  unload_session ();
 	void close_session(); 
diff --git a/gtk2_ardour/ardour_ui_ed.cc b/gtk2_ardour/ardour_ui_ed.cc
index 47d035b54e..2ebcb765c3 100644
--- a/gtk2_ardour/ardour_ui_ed.cc
+++ b/gtk2_ardour/ardour_ui_ed.cc
@@ -92,7 +92,7 @@ ARDOUR_UI::install_actions ()
 
 	/* the real actions */
 
-	act = ActionManager::register_action (main_actions, X_("New"), _("New"),  bind (mem_fun(*this, &ARDOUR_UI::new_session), false, string ()));
+	act = ActionManager::register_action (main_actions, X_("New"), _("New"),  bind (mem_fun(*this, &ARDOUR_UI::new_session), string ()));
 
 	ActionManager::register_action (main_actions, X_("Open"), _("Open"),  mem_fun(*this, &ARDOUR_UI::open_session));
 	ActionManager::register_action (main_actions, X_("Recent"), _("Recent"),  mem_fun(*this, &ARDOUR_UI::open_recent_session));
diff --git a/gtk2_ardour/main.cc b/gtk2_ardour/main.cc
index 3e0d6d4e62..1004de19c2 100644
--- a/gtk2_ardour/main.cc
+++ b/gtk2_ardour/main.cc
@@ -79,8 +79,6 @@ shutdown (int status)
 	} else {
 
 		if (ui) {
-			msg = _("stopping user interface\n");
-			write (1, msg, strlen (msg));
 			ui->kill();
 		}
 		
@@ -301,7 +299,7 @@ maybe_load_session ()
 	if (!session_name.length()) {
 		ui->hide_splash ();
 		if (!Config->get_no_new_session_dialog()) {
-		       ui->new_session (true);
+		       ui->new_session ();
 		}
 
 		return true;
@@ -326,7 +324,10 @@ To create it from the command line, start ardour as \"ardour --new %1"), path) <
 			return false;
 		}
 
-		ui->load_session (path, name);
+		if (ui->load_session (path, name)) {
+			/* it failed */
+			return false;
+		}
 
 	} else {
 
@@ -338,7 +339,7 @@ To create it from the command line, start ardour as \"ardour --new %1"), path) <
 		/* Show the NSD */
 		ui->hide_splash ();
 		if (!Config->get_no_new_session_dialog()) {
-		       ui->new_session (true);
+		       ui->new_session ();
 		}
 	}
 
diff --git a/libs/ardour/ardour/audio_diskstream.h b/libs/ardour/ardour/audio_diskstream.h
index 7c00885228..1da8903a41 100644
--- a/libs/ardour/ardour/audio_diskstream.h
+++ b/libs/ardour/ardour/audio_diskstream.h
@@ -173,33 +173,39 @@ class AudioDiskstream : public Diskstream
   private:
 
 	struct ChannelInfo {
-
-		Sample     *playback_wrap_buffer;
-		Sample     *capture_wrap_buffer;
-		Sample     *speed_buffer;
-
-		float       peak_power;
 	    
-  	        boost::shared_ptr<AudioFileSource> fades_source;
-	        boost::shared_ptr<AudioFileSource> write_source;
-
-		Port         *source;
-		Sample       *current_capture_buffer;
-		Sample       *current_playback_buffer;
+	    ChannelInfo ();
+	    ~ChannelInfo ();
 
-		RingBufferNPT<Sample> *playback_buf;
-		RingBufferNPT<Sample> *capture_buf;
+	    void init (nframes_t buffer_size, nframes_t speed_buffer_size, nframes_t wrap_buffer_size);
+	    void release ();
 
-		Sample* scrub_buffer;
-		Sample* scrub_forward_buffer;
-		Sample* scrub_reverse_buffer;
-
-		RingBufferNPT<Sample>::rw_vector playback_vector;
-		RingBufferNPT<Sample>::rw_vector capture_vector;
-
-		RingBufferNPT<CaptureTransition> * capture_transition_buf;
-		// the following are used in the butler thread only
-		nframes_t                     curr_capture_cnt;
+	    Sample     *playback_wrap_buffer;
+	    Sample     *capture_wrap_buffer;
+	    Sample     *speed_buffer;
+	    
+	    float       peak_power;
+	    
+	    boost::shared_ptr<AudioFileSource> fades_source;
+	    boost::shared_ptr<AudioFileSource> write_source;
+	    
+	    Port         *source;
+	    Sample       *current_capture_buffer;
+	    Sample       *current_playback_buffer;
+	    
+	    RingBufferNPT<Sample> *playback_buf;
+	    RingBufferNPT<Sample> *capture_buf;
+	    
+	    Sample* scrub_buffer;
+	    Sample* scrub_forward_buffer;
+	    Sample* scrub_reverse_buffer;
+	    
+	    RingBufferNPT<Sample>::rw_vector playback_vector;
+	    RingBufferNPT<Sample>::rw_vector capture_vector;
+	    
+	    RingBufferNPT<CaptureTransition> * capture_transition_buf;
+	    // the following are used in the butler thread only
+	    nframes_t                     curr_capture_cnt;
 	};
 
 	/* The two central butler operations */
diff --git a/libs/ardour/ardour/audioengine.h b/libs/ardour/ardour/audioengine.h
index 7274f5646e..83d075a311 100644
--- a/libs/ardour/ardour/audioengine.h
+++ b/libs/ardour/ardour/audioengine.h
@@ -197,8 +197,7 @@ class AudioEngine : public sigc::trackable
 	jack_client_t       *_jack;
 	std::string           jack_client_name;
 	Glib::Mutex           _process_lock;
-	Glib::Mutex           session_remove_lock;
-    Glib::Cond            session_removed;
+	Glib::Cond            session_removed;
 	bool                  session_remove_pending;
 	bool                 _running;
 	bool                 _has_run;
diff --git a/libs/ardour/ardour/io.h b/libs/ardour/ardour/io.h
index eb332398da..7c198bb72a 100644
--- a/libs/ardour/ardour/io.h
+++ b/libs/ardour/ardour/io.h
@@ -199,13 +199,13 @@ class IO : public PBD::StatefulDestructible
 
     static void update_meters();
 
-private: 
+  private: 
 
     static sigc::signal<void>   Meter;
     static Glib::StaticMutex    m_meter_signal_lock;
     sigc::connection            m_meter_connection;
 
-public:
+  public:
 
 	/* automation */
 
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index c71403e125..5aa53e274f 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -933,6 +933,7 @@ class Session : public PBD::StatefulDestructible
 	
   private:
 	int  create (bool& new_session, string* mix_template, nframes_t initial_length);
+	void destroy ();
 
 	nframes_t compute_initial_length ();
 
diff --git a/libs/ardour/audio_diskstream.cc b/libs/ardour/audio_diskstream.cc
index 66b34956fe..ef3173e87b 100644
--- a/libs/ardour/audio_diskstream.cc
+++ b/libs/ardour/audio_diskstream.cc
@@ -97,34 +97,6 @@ AudioDiskstream::AudioDiskstream (Session& sess, const XMLNode& node)
 }
 
 void
-AudioDiskstream::init_channel (ChannelInfo &chan)
-{
-	chan.playback_wrap_buffer = 0;
-	chan.capture_wrap_buffer = 0;
-	chan.speed_buffer = 0;
-	chan.peak_power = 0.0f;
-	chan.source = 0;
-	chan.current_capture_buffer = 0;
-	chan.current_playback_buffer = 0;
-	chan.curr_capture_cnt = 0;
-	
-	chan.playback_buf = new RingBufferNPT<Sample> (_session.diskstream_buffer_size());
-	chan.capture_buf = new RingBufferNPT<Sample> (_session.diskstream_buffer_size());
-	chan.capture_transition_buf = new RingBufferNPT<CaptureTransition> (128);
-	
-	
-	/* touch the ringbuffer buffers, which will cause
-	   them to be mapped into locked physical RAM if
-	   we're running with mlockall(). this doesn't do
-	   much if we're not.  
-	*/
-	memset (chan.playback_buf->buffer(), 0, sizeof (Sample) * chan.playback_buf->bufsize());
-	memset (chan.capture_buf->buffer(), 0, sizeof (Sample) * chan.capture_buf->bufsize());
-	memset (chan.capture_transition_buf->buffer(), 0, sizeof (CaptureTransition) * chan.capture_transition_buf->bufsize());
-}
-
-
-void
 AudioDiskstream::init (Diskstream::Flag f)
 {
 	Diskstream::init(f);
@@ -141,44 +113,19 @@ AudioDiskstream::init (Diskstream::Flag f)
 	assert(_n_channels == 1);
 }
 
-void
-AudioDiskstream::destroy_channel (ChannelInfo &chan)
-{
-	if (chan.write_source) {
-		chan.write_source.reset ();
-	}
-		
-	if (chan.speed_buffer) {
-		delete [] chan.speed_buffer;
-	}
-
-	if (chan.playback_wrap_buffer) {
-		delete [] chan.playback_wrap_buffer;
-	}
-	if (chan.capture_wrap_buffer) {
-		delete [] chan.capture_wrap_buffer;
-	}
-	
-	delete chan.playback_buf;
-	delete chan.capture_buf;
-	delete chan.capture_transition_buf;
-	
-	chan.playback_buf = 0;
-	chan.capture_buf = 0;
-}
-
 AudioDiskstream::~AudioDiskstream ()
 {
+	notify_callbacks ();
+
 	{
 		/* don't be holding this lock as we exit the destructor, glib will wince
 		   visibly since the mutex gets destroyed before we release it.
 		*/
 
 		Glib::Mutex::Lock lm (state_lock);
-		
-		for (ChannelList::iterator chan = channels.begin(); chan != channels.end(); ++chan)
-			destroy_channel((*chan));
-		
+		for (ChannelList::iterator chan = channels.begin(); chan != channels.end(); ++chan) {
+			(*chan).release ();
+		}
 		channels.clear();
 	}
 }
@@ -2107,15 +2054,19 @@ AudioDiskstream::add_channel ()
 {
 	/* XXX need to take lock??? */
 
-	ChannelInfo chan;
+	/* this copies the ChannelInfo, which currently has no buffers. kind
+	   of pointless really, but we want the channels list to contain
+	   actual objects, not pointers to objects. mostly for convenience,
+	   which isn't much in evidence.
+	*/
 
-	init_channel (chan);
+	channels.push_back (ChannelInfo());
 
-	chan.speed_buffer = new Sample[speed_buffer_size];
-	chan.playback_wrap_buffer = new Sample[wrap_buffer_size];
-	chan.capture_wrap_buffer = new Sample[wrap_buffer_size];
+	/* now allocate the buffers */
 
-	channels.push_back (chan);
+	channels.back().init (_session.diskstream_buffer_size(), 
+			      speed_buffer_size,
+			      wrap_buffer_size);
 
 	_n_channels = channels.size();
 
@@ -2127,10 +2078,8 @@ AudioDiskstream::remove_channel ()
 {
 	if (channels.size() > 1) {
 		/* XXX need to take lock??? */
-		ChannelInfo & chan = channels.back();
-		destroy_channel (chan);
+		channels.back().release ();
 		channels.pop_back();
-
 		_n_channels = channels.size();
 		return 0;
 	}
@@ -2310,3 +2259,82 @@ AudioDiskstream::can_become_destructive (bool& requires_bounce) const
 	requires_bounce = false;
 	return true;
 }
+
+AudioDiskstream::ChannelInfo::ChannelInfo ()
+{
+	playback_wrap_buffer = 0;
+	capture_wrap_buffer = 0;
+	speed_buffer = 0;
+	peak_power = 0.0f;
+	source = 0;
+	current_capture_buffer = 0;
+	current_playback_buffer = 0;
+	curr_capture_cnt = 0;
+	playback_buf = 0;
+	capture_buf = 0;
+	capture_transition_buf = 0;
+}
+
+void
+AudioDiskstream::ChannelInfo::init (nframes_t bufsize, nframes_t speed_size, nframes_t wrap_size)
+{
+	speed_buffer = new Sample[speed_size];
+	playback_wrap_buffer = new Sample[wrap_size];
+	capture_wrap_buffer = new Sample[wrap_size];
+
+	playback_buf = new RingBufferNPT<Sample> (bufsize);
+	capture_buf = new RingBufferNPT<Sample> (bufsize);
+	capture_transition_buf = new RingBufferNPT<CaptureTransition> (128);
+	
+	/* touch the ringbuffer buffers, which will cause
+	   them to be mapped into locked physical RAM if
+	   we're running with mlockall(). this doesn't do
+	   much if we're not.  
+	*/
+
+	memset (playback_buf->buffer(), 0, sizeof (Sample) * playback_buf->bufsize());
+	memset (capture_buf->buffer(), 0, sizeof (Sample) * capture_buf->bufsize());
+	memset (capture_transition_buf->buffer(), 0, sizeof (CaptureTransition) * capture_transition_buf->bufsize());
+}
+
+AudioDiskstream::ChannelInfo::~ChannelInfo ()
+{
+}
+
+void
+AudioDiskstream::ChannelInfo::release ()
+{
+	if (write_source) {
+		write_source.reset ();
+	}
+		
+	if (speed_buffer) {
+		delete [] speed_buffer;
+		speed_buffer = 0;
+	}
+
+	if (playback_wrap_buffer) {
+		delete [] playback_wrap_buffer;
+		playback_wrap_buffer = 0;
+	}
+
+	if (capture_wrap_buffer) {
+		delete [] capture_wrap_buffer;
+		capture_wrap_buffer = 0;
+	}
+	
+	if (playback_buf) {
+		delete playback_buf;
+		playback_buf = 0;
+	}
+
+	if (capture_buf) {
+		delete capture_buf;
+		capture_buf = 0;
+	}
+
+	if (capture_transition_buf) {
+		delete capture_transition_buf;
+		capture_transition_buf = 0;
+	}
+}
diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index 39c5ddcdab..128fc37eb1 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -45,6 +45,12 @@ using namespace PBD;
 
 gint AudioEngine::m_meter_exit;
 
+static void 
+ardour_jack_error (const char* msg) 
+{
+	error << "JACK: " << msg << endmsg;
+}
+
 AudioEngine::AudioEngine (string client_name) 
 	: ports (new Ports)
 {
@@ -76,11 +82,16 @@ AudioEngine::AudioEngine (string client_name)
 
 AudioEngine::~AudioEngine ()
 {
-	if (_running) {
-		jack_client_close (_jack);
+	{
+		Glib::Mutex::Lock tm (_process_lock);
+		session_removed.signal ();
+		
+		if (_running) {
+			jack_client_close (_jack);
+		}
+		
+		stop_metering_thread ();
 	}
-
-	stop_metering_thread ();
 }
 
 void
@@ -407,8 +418,26 @@ AudioEngine::meter_thread ()
 void 
 AudioEngine::set_session (Session *s)
 {
+	Glib::Mutex::Lock pl (_process_lock);
+
 	if (!session) {
+
 		session = s;
+
+		nframes_t blocksize = jack_get_buffer_size (_jack);
+		
+		/* page in as much of the session process code as we
+		   can before we really start running.
+		*/
+		
+		session->process (blocksize);
+		session->process (blocksize);
+		session->process (blocksize);
+		session->process (blocksize);
+		session->process (blocksize);
+		session->process (blocksize);
+		session->process (blocksize);
+		session->process (blocksize);
 	}
 }
 
@@ -422,12 +451,10 @@ AudioEngine::remove_session ()
 		if (session) {
 			session_remove_pending = true;
 			session_removed.wait(_process_lock);
-		} 
+		}
 
 	} else {
-
 		session = 0;
-
 	}
 	
 	remove_all_ports ();
@@ -461,8 +488,6 @@ AudioEngine::register_input_port (DataType type, const string& portname)
 		return newport;
 
 	} else {
-
-		_process_lock.unlock();
 		throw PortRegistrationFailure();
 	}
 
@@ -501,8 +526,6 @@ AudioEngine::register_output_port (DataType type, const string& portname)
 		return newport;
 
 	} else {
-
-		_process_lock.unlock();
 		throw PortRegistrationFailure ();
 	}
 
@@ -1015,6 +1038,8 @@ AudioEngine::connect_to_jack (string client_name)
 	if (status & JackNameNotUnique) {
 		jack_client_name = jack_get_client_name (_jack);
 	}
+
+	jack_set_error_function (ardour_jack_error);
 	
 	return 0;
 }
diff --git a/libs/ardour/io.cc b/libs/ardour/io.cc
index 77f3a33ff2..1c72697347 100644
--- a/libs/ardour/io.cc
+++ b/libs/ardour/io.cc
@@ -53,6 +53,7 @@ extern "C" int isnan (double);
 extern "C" int isinf (double);
 #endif
 
+#define BLOCK_PROCESS_CALLBACK() Glib::Mutex::Lock em (_session.engine().process_lock())
 
 using namespace std;
 using namespace ARDOUR;
@@ -624,7 +625,7 @@ IO::disconnect_input (Port* our_port, string other_port, void* src)
 	}
 
 	{ 
-		Glib::Mutex::Lock em (_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		
 		{
 			Glib::Mutex::Lock lm (io_lock);
@@ -660,7 +661,7 @@ IO::connect_input (Port* our_port, string other_port, void* src)
 	}
 
 	{
-		Glib::Mutex::Lock em(_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		
 		{
 			Glib::Mutex::Lock lm (io_lock);
@@ -694,7 +695,7 @@ IO::disconnect_output (Port* our_port, string other_port, void* src)
 	}
 
 	{
-		Glib::Mutex::Lock em(_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		
 		{
 			Glib::Mutex::Lock lm (io_lock);
@@ -727,7 +728,8 @@ IO::connect_output (Port* our_port, string other_port, void* src)
 	}
 
 	{
-		Glib::Mutex::Lock em(_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
+
 		
 		{
 			Glib::Mutex::Lock lm (io_lock);
@@ -786,7 +788,8 @@ IO::remove_output_port (Port* port, void* src)
 	IOChange change (NoChange);
 
 	{
-		Glib::Mutex::Lock em(_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
+
 		
 		{
 			Glib::Mutex::Lock lm (io_lock);
@@ -844,7 +847,8 @@ IO::add_output_port (string destination, void* src, DataType type)
 		type = _default_type;
 
 	{
-		Glib::Mutex::Lock em(_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
+
 		
 		{ 
 			Glib::Mutex::Lock lm (io_lock);
@@ -896,7 +900,8 @@ IO::remove_input_port (Port* port, void* src)
 	IOChange change (NoChange);
 
 	{
-		Glib::Mutex::Lock em(_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
+
 		
 		{
 			Glib::Mutex::Lock lm (io_lock);
@@ -956,7 +961,7 @@ IO::add_input_port (string source, void* src, DataType type)
 		type = _default_type;
 
 	{
-		Glib::Mutex::Lock em (_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		
 		{ 
 			Glib::Mutex::Lock lm (io_lock);
@@ -1008,7 +1013,7 @@ int
 IO::disconnect_inputs (void* src)
 {
 	{ 
-		Glib::Mutex::Lock em (_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		
 		{
 			Glib::Mutex::Lock lm (io_lock);
@@ -1028,7 +1033,7 @@ int
 IO::disconnect_outputs (void* src)
 {
 	{
-		Glib::Mutex::Lock em (_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		
 		{
 			Glib::Mutex::Lock lm (io_lock);
@@ -1090,7 +1095,7 @@ IO::ensure_inputs_locked (uint32_t n, bool clear, void* src)
 			setup_peak_meters ();
 			reset_panner ();
 			/* pass it on */
-			throw err;
+			throw AudioEngine::PortRegistrationFailure();
 		}
 		
 		_inputs.push_back (input_port);
@@ -1140,7 +1145,7 @@ IO::ensure_io (uint32_t nin, uint32_t nout, bool clear, void* src)
 	}
 
 	{
-		Glib::Mutex::Lock em (_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		Glib::Mutex::Lock lm (io_lock);
 
 		Port* port;
@@ -1195,7 +1200,7 @@ IO::ensure_io (uint32_t nin, uint32_t nout, bool clear, void* src)
 				setup_peak_meters ();
 				reset_panner ();
 				/* pass it on */
-				throw err;
+				throw AudioEngine::PortRegistrationFailure();
 			}
 		
 			_inputs.push_back (port);
@@ -1228,7 +1233,7 @@ IO::ensure_io (uint32_t nin, uint32_t nout, bool clear, void* src)
 				setup_peak_meters ();
 				reset_panner ();
 				/* pass it on */
-				throw err;
+				throw AudioEngine::PortRegistrationFailure ();
 			}
 		
 			_outputs.push_back (port);
@@ -1289,7 +1294,7 @@ IO::ensure_inputs (uint32_t n, bool clear, bool lockit, void* src)
 	}
 	
 	if (lockit) {
-		Glib::Mutex::Lock em (_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		Glib::Mutex::Lock im (io_lock);
 		changed = ensure_inputs_locked (n, clear, src);
 	} else {
@@ -1391,7 +1396,7 @@ IO::ensure_outputs (uint32_t n, bool clear, bool lockit, void* src)
 	/* XXX caller should hold io_lock, but generally doesn't */
 
 	if (lockit) {
-		Glib::Mutex::Lock em (_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		Glib::Mutex::Lock im (io_lock);
 		changed = ensure_outputs_locked (n, clear, src);
 	} else {
@@ -2191,7 +2196,7 @@ IO::use_input_connection (Connection& c, void* src)
 	uint32_t limit;
 
 	{
-		Glib::Mutex::Lock lm (_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		Glib::Mutex::Lock lm2 (io_lock);
 		
 		limit = c.nports();
@@ -2269,7 +2274,7 @@ IO::use_output_connection (Connection& c, void* src)
 	uint32_t limit;	
 
 	{
-		Glib::Mutex::Lock lm (_session.engine().process_lock());
+		BLOCK_PROCESS_CALLBACK ();
 		Glib::Mutex::Lock lm2 (io_lock);
 
 		limit = c.nports();
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 45be26c598..c6cd6528d3 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -281,12 +281,13 @@ Session::Session (AudioEngine &eng,
 	if (new_session) {
 		if (create (new_session, mix_template, compute_initial_length())) {
 			cerr << "create failed\n";
+			destroy ();
 			throw failed_constructor ();
 		}
 	}
 	
 	if (second_stage_init (new_session)) {
-		cerr << "2nd state failed\n";
+		destroy ();
 		throw failed_constructor ();
 	}
 	
@@ -346,6 +347,7 @@ Session::Session (AudioEngine &eng,
 
 	if (new_session) {
 		if (create (new_session, 0, initial_length)) {
+			destroy ();
 			throw failed_constructor ();
 		}
 	}
@@ -373,6 +375,7 @@ Session::Session (AudioEngine &eng,
 	Config->set_output_auto_connect (output_ac);
 
 	if (second_stage_init (new_session)) {
+		destroy ();
 		throw failed_constructor ();
 	}
 	
@@ -389,6 +392,12 @@ Session::Session (AudioEngine &eng,
 
 Session::~Session ()
 {
+	destroy ();
+}
+
+void
+Session::destroy ()
+{
 	/* if we got to here, leaving pending capture state around
 	   is a mistake.
 	*/
@@ -2930,6 +2939,7 @@ Session::audio_path_from_name (string name, uint32_t nchan, uint32_t chan, bool
 
 		if (cnt > limit) {
 			error << string_compose(_("There are already %1 recordings for %2, which I consider too many."), limit, name) << endmsg;
+			destroy ();
 			throw failed_constructor();
 		}
 	}
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index 0afa682d58..0c2961c82a 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -99,12 +99,14 @@ void
 Session::first_stage_init (string fullpath, string snapshot_name)
 {
 	if (fullpath.length() == 0) {
+		destroy ();
 		throw failed_constructor();
 	}
 
 	char buf[PATH_MAX+1];
 	if (!realpath (fullpath.c_str(), buf) && (errno != ENOENT)) {
 		error << string_compose(_("Could not use path %1 (%s)"), buf, strerror(errno)) << endmsg;
+		destroy ();
 		throw failed_constructor();
 	}
 
@@ -155,7 +157,7 @@ Session::first_stage_init (string fullpath, string snapshot_name)
 	_worst_output_latency = 0;
 	_worst_input_latency = 0;
 	_worst_track_latency = 0;
-	_state_of_the_state = StateOfTheState(CannotSave|InitialConnecting|Loading);
+	_state_of_the_state = StateOfTheState(CannotSave|InitialConnecting|Loading|Deletion);
 	_slave = 0;
 	butler_mixdown_buffer = 0;
 	butler_gain_buffer = 0;
@@ -307,7 +309,13 @@ Session::second_stage_init (bool new_session)
 	_engine.Halted.connect (mem_fun (*this, &Session::engine_halted));
 	_engine.Xrun.connect (mem_fun (*this, &Session::xrun_recovery));
 
-	when_engine_running();
+	try {
+		when_engine_running();
+	}
+
+	catch (...) {
+		return -1;
+	}
 
 	send_full_time_code ();
 	_engine.transport_locate (0);