RCU-ification of AudioEngine port list, and DiskStreams. not well tested, but basically functional. better to get this in now rather than later.

git-svn-id: svn://localhost/ardour2/trunk@828 d708f5d6-7413-0410-9779-e7cbd77b26cf

20 files changed, 308 insertions, 285 deletions

diff --git a/libs/ardour/ardour/audio_diskstream.h b/libs/ardour/ardour/audio_diskstream.h
index 0cc2079d8e..18f8328cfd 100644
--- a/libs/ardour/ardour/audio_diskstream.h
+++ b/libs/ardour/ardour/audio_diskstream.h
@@ -59,12 +59,10 @@ class AudioDiskstream : public Diskstream
   public:
 	AudioDiskstream (Session &, const string& name, Diskstream::Flag f = Recordable);
 	AudioDiskstream (Session &, const XMLNode&);
+	~AudioDiskstream();
 
 	const PBD::ID& id() const { return _id; }
 
-	// FIXME
-	AudioDiskstream& ref() { _refcnt++; return *this; }
-
 	float playback_buffer_load() const;
 	float capture_buffer_load() const;
 
@@ -176,9 +174,6 @@ class AudioDiskstream : public Diskstream
 
   private:
 
-	/* use unref() to destroy a diskstream */
-	~AudioDiskstream();
-
 	struct ChannelInfo {
 
 		Sample     *playback_wrap_buffer;
diff --git a/libs/ardour/ardour/audio_track.h b/libs/ardour/ardour/audio_track.h
index 9892179085..33010dc880 100644
--- a/libs/ardour/ardour/audio_track.h
+++ b/libs/ardour/ardour/audio_track.h
@@ -46,7 +46,7 @@ class AudioTrack : public Track
 	int silent_roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nframes_t end_frame, 
 		jack_nframes_t offset, bool can_record, bool rec_monitors_input);
 
-	AudioDiskstream& audio_diskstream() const;
+	boost::shared_ptr<AudioDiskstream> audio_diskstream() const;
 
 	int use_diskstream (string name);
 	int use_diskstream (const PBD::ID& id);
@@ -71,7 +71,7 @@ class AudioTrack : public Track
 	uint32_t n_process_buffers ();
 	
   private:
-	int  set_diskstream (AudioDiskstream&, void *);
+	int  set_diskstream (boost::shared_ptr<AudioDiskstream>, void *);
 	int  deprecated_use_diskstream_connections ();
 	void set_state_part_two ();
 	void set_state_part_three ();
diff --git a/libs/ardour/ardour/audioengine.h b/libs/ardour/ardour/audioengine.h
index e7500fc7a2..00a0ce6b19 100644
--- a/libs/ardour/ardour/audioengine.h
+++ b/libs/ardour/ardour/audioengine.h
@@ -31,6 +31,8 @@
 
 #include <glibmm/thread.h>
 
+#include <pbd/rcu.h>
+
 #include <ardour/ardour.h>
 #include <jack/jack.h>
 #include <jack/transport.h>
@@ -189,7 +191,6 @@ class AudioEngine : public sigc::trackable
 	ARDOUR::Session      *session;
 	jack_client_t       *_jack;
 	std::string           jack_client_name;
-	Glib::Mutex           port_lock;
 	Glib::Mutex           _process_lock;
 	Glib::Mutex           session_remove_lock;
     Glib::Cond            session_removed;
@@ -208,7 +209,7 @@ class AudioEngine : public sigc::trackable
 	int                  _usecs_per_cycle;
 
 	typedef std::set<Port*> Ports;
-	Ports ports;
+	SerializedRCUManager<Ports> ports;
 
 	int    process_callback (jack_nframes_t nframes);
 	void   remove_all_ports ();
diff --git a/libs/ardour/ardour/diskstream.h b/libs/ardour/ardour/diskstream.h
index e0202a4fae..bcd418b452 100644
--- a/libs/ardour/ardour/diskstream.h
+++ b/libs/ardour/ardour/diskstream.h
@@ -34,6 +34,7 @@
 #include <pbd/fastlog.h>
 #include <pbd/ringbufferNPT.h>
 #include <pbd/stateful.h>
+#include <pbd/destructible.h>
 
 #include <ardour/ardour.h>
 #include <ardour/configuration.h>
@@ -43,7 +44,6 @@
 #include <ardour/port.h>
 #include <ardour/utils.h>
 
-
 struct tm;
 
 namespace ARDOUR {
@@ -54,7 +54,7 @@ class Session;
 class Playlist;
 class IO;
 
-class Diskstream : public Stateful, public sigc::trackable
+ class Diskstream : public Stateful, public sigc::trackable, public PBD::Destructible
 {	
   public:
 	enum Flag {
@@ -63,16 +63,16 @@ class Diskstream : public Stateful, public sigc::trackable
 		Destructive = 0x4
 	};
 
+	Diskstream (Session &, const string& name, Flag f = Recordable);
+	Diskstream (Session &, const XMLNode&);
+	virtual ~Diskstream();
+
 	string      name () const { return _name; }
 	virtual int set_name (string str);
 
 	ARDOUR::IO* io() const { return _io; }
 	void set_io (ARDOUR::IO& io);
 
-	virtual Diskstream& ref() { _refcnt++; return *this; }
-	void     unref() { if (_refcnt) _refcnt--; if (_refcnt == 0) delete this; }
-	uint32_t refcnt() const { return _refcnt; }
-
 	virtual float playback_buffer_load() const = 0;
 	virtual float capture_buffer_load() const = 0;
 
@@ -148,15 +148,11 @@ class Diskstream : public Stateful, public sigc::trackable
 
 	static sigc::signal<void>                DiskOverrun;
 	static sigc::signal<void>                DiskUnderrun;
-	static sigc::signal<void,Diskstream*>    DiskstreamCreated; // XXX use a ref with sigc2
 	static sigc::signal<void,list<Source*>*> DeleteSources;
 
   protected:
 	friend class Session;
 
-	Diskstream (Session &, const string& name, Flag f = Recordable);
-	Diskstream (Session &, const XMLNode&);
-
 	/* the Session is the only point of access for these because they require
 	 * that the Session is "inactive" while they are called.
 	 */
@@ -187,9 +183,6 @@ class Diskstream : public Stateful, public sigc::trackable
 
 	//private:
 	
-	/** Use unref() to destroy a diskstream */
-	virtual ~Diskstream();
-
 	enum TransitionType {
 		CaptureStart = 0,
 		CaptureEnd
@@ -304,8 +297,6 @@ class Diskstream : public Stateful, public sigc::trackable
 	jack_nframes_t scrub_buffer_size;
 	jack_nframes_t scrub_offset;
 
-	uint32_t _refcnt;
-
 	sigc::connection ports_created_c;
 	sigc::connection plmod_connection;
 	sigc::connection plstate_connection;
diff --git a/libs/ardour/ardour/route.h b/libs/ardour/ardour/route.h
index d1db818e40..ff7aa6184c 100644
--- a/libs/ardour/ardour/route.h
+++ b/libs/ardour/ardour/route.h
@@ -35,6 +35,7 @@
 #include <pbd/undo.h>
 #include <pbd/stateful.h> 
 #include <pbd/controllable.h>
+#include <pbd/destructible.h>
 
 #include <ardour/ardour.h>
 #include <ardour/io.h>
@@ -55,7 +56,7 @@ enum mute_type {
     MAIN_OUTS =    0x8
 };
 
-class Route : public IO
+ class Route : public IO, public PBD::Destructible
 {
   protected:
 
@@ -192,8 +193,6 @@ class Route : public IO
 	sigc::signal<void>       active_changed;
 	sigc::signal<void,void*> meter_change;
 
-	sigc::signal<void> GoingAway;
-
 	/* gui's call this for their own purposes. */
 
 	sigc::signal<void,std::string,void*> gui_changed;
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index d067de4e68..3763ebe91e 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -270,8 +270,9 @@ class Session : public sigc::trackable, public Stateful
 	vector<Sample*>& get_silent_buffers (uint32_t howmany);
 	vector<Sample*>& get_send_buffers () { return _send_buffers; }
 
-	Diskstream* diskstream_by_id (const PBD::ID& id);
-	Diskstream* diskstream_by_name (string name);
+	void add_diskstream (boost::shared_ptr<Diskstream>);
+	boost::shared_ptr<Diskstream> diskstream_by_id (const PBD::ID& id);
+	boost::shared_ptr<Diskstream> diskstream_by_name (string name);
 
 	bool have_captured() const { return _have_captured; }
 
@@ -281,9 +282,8 @@ class Session : public sigc::trackable, public Stateful
 	uint32_t get_next_diskstream_id() const { return n_diskstreams(); }
 	uint32_t n_diskstreams() const;
 	
-	typedef list<Diskstream *> DiskstreamList;
-
-	typedef std::list<boost::shared_ptr<Route> > RouteList; 
+	typedef std::list<boost::shared_ptr<Diskstream> > DiskstreamList;
+	typedef std::list<boost::shared_ptr<Route> >      RouteList; 
 
 	boost::shared_ptr<RouteList> get_routes() const {
 		return routes.reader ();
@@ -346,7 +346,6 @@ class Session : public sigc::trackable, public Stateful
 	sigc::signal<void> HaltOnXrun;
 
 	sigc::signal<void,boost::shared_ptr<Route> > RouteAdded;
-	sigc::signal<void,Diskstream*> DiskstreamAdded; // FIXME: make a shared_ptr
 
 	void request_roll ();
 	void request_bounded_roll (jack_nframes_t start, jack_nframes_t end);
@@ -1509,10 +1508,9 @@ class Session : public sigc::trackable, public Stateful
 
 	/* disk-streams */
 
-	DiskstreamList  diskstreams; 
-	mutable Glib::RWLock diskstream_lock;
+	SerializedRCUManager<DiskstreamList>  diskstreams; 
+
 	uint32_t dstream_buffer_size;
-	void add_diskstream (Diskstream*);
 	int  load_diskstreams (const XMLNode&);
 
 	/* routes stuff */
@@ -1580,7 +1578,7 @@ class Session : public sigc::trackable, public Stateful
 	Playlist *XMLPlaylistFactory (const XMLNode&);
 
 	void playlist_length_changed (Playlist *);
-	void diskstream_playlist_changed (Diskstream *);
+	void diskstream_playlist_changed (boost::shared_ptr<Diskstream>);
 
 	/* NAMED SELECTIONS */
 
diff --git a/libs/ardour/ardour/track.h b/libs/ardour/ardour/track.h
index 4e2af5c80e..ec444e78dc 100644
--- a/libs/ardour/ardour/track.h
+++ b/libs/ardour/ardour/track.h
@@ -19,6 +19,8 @@
 #ifndef __ardour_track_h__
 #define __ardour_track_h__
 
+#include <boost/shared_ptr.hpp>
+
 #include <ardour/route.h>
 
 namespace ARDOUR {
@@ -50,7 +52,7 @@ class Track : public Route
 
 	virtual bool can_record();
 
-	Diskstream& diskstream() const { return *_diskstream; }
+	boost::shared_ptr<Diskstream> diskstream() const { return _diskstream; }
 
 	virtual int use_diskstream (string name) = 0;
 	virtual int use_diskstream (const PBD::ID& id) = 0;
@@ -100,7 +102,7 @@ class Track : public Route
 
 	virtual uint32_t n_process_buffers () = 0;
 	
-	Diskstream *_diskstream;
+	boost::shared_ptr<Diskstream> _diskstream;
 	MeterPoint  _saved_meter_point;
 	TrackMode   _mode;
 
diff --git a/libs/ardour/audio_diskstream.cc b/libs/ardour/audio_diskstream.cc
index d3e64104a0..baefeff377 100644
--- a/libs/ardour/audio_diskstream.cc
+++ b/libs/ardour/audio_diskstream.cc
@@ -71,8 +71,6 @@ AudioDiskstream::AudioDiskstream (Session &sess, const string &name, Diskstream:
 	use_new_playlist ();
 
 	in_set_state = false;
-
-	DiskstreamCreated (this); /* EMIT SIGNAL */
 }
 	
 AudioDiskstream::AudioDiskstream (Session& sess, const XMLNode& node)
@@ -92,8 +90,6 @@ AudioDiskstream::AudioDiskstream (Session& sess, const XMLNode& node)
 	if (destructive()) {
 		use_destructive_playlist ();
 	}
-
-	DiskstreamCreated (this); /* EMIT SIGNAL */
 }
 
 void
diff --git a/libs/ardour/audio_track.cc b/libs/ardour/audio_track.cc
index 2f33012546..98a2262f86 100644
--- a/libs/ardour/audio_track.cc
+++ b/libs/ardour/audio_track.cc
@@ -55,9 +55,10 @@ AudioTrack::AudioTrack (Session& sess, string name, Route::Flag flag, TrackMode
 		dflags = AudioDiskstream::Flag (dflags | AudioDiskstream::Destructive);
 	}
 
-	AudioDiskstream* ds = new AudioDiskstream (_session, name, dflags);
-	
-	set_diskstream (*ds, this);
+	boost::shared_ptr<AudioDiskstream> ds (new AudioDiskstream (_session, name, dflags));
+	_session.add_diskstream (ds);
+
+	set_diskstream (boost::dynamic_pointer_cast<AudioDiskstream> (ds), this);
 }
 
 AudioTrack::AudioTrack (Session& sess, const XMLNode& node)
@@ -73,18 +74,18 @@ AudioTrack::~AudioTrack ()
 int
 AudioTrack::deprecated_use_diskstream_connections ()
 {
-	AudioDiskstream& diskstream = audio_diskstream();
+	boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 
-	if (diskstream.deprecated_io_node == 0) {
+	if (diskstream->deprecated_io_node == 0) {
 		return 0;
 	}
 
 	const XMLProperty* prop;
-	XMLNode& node (*diskstream.deprecated_io_node);
+	XMLNode& node (*diskstream->deprecated_io_node);
 
 	/* don't do this more than once. */
 
-	diskstream.deprecated_io_node = 0;
+	diskstream->deprecated_io_node = 0;
 
 	set_input_minimum (-1);
 	set_input_maximum (-1);
@@ -125,17 +126,13 @@ AudioTrack::deprecated_use_diskstream_connections ()
 }
 
 int
-AudioTrack::set_diskstream (AudioDiskstream& ds, void *src)
+AudioTrack::set_diskstream (boost::shared_ptr<AudioDiskstream> ds, void *src)
 {
-	if (_diskstream) {
-		_diskstream->unref();
-	}
-
-	_diskstream = &ds.ref();
+	_diskstream = ds;
 	_diskstream->set_io (*this);
 	_diskstream->set_destructive (_mode == Destructive);
 
-	if (audio_diskstream().deprecated_io_node) {
+	if (audio_diskstream()->deprecated_io_node) {
 
 		if (!connecting_legal) {
 			ConnectingLegal.connect (mem_fun (*this, &AudioTrack::deprecated_use_diskstream_connections));
@@ -158,33 +155,33 @@ AudioTrack::set_diskstream (AudioDiskstream& ds, void *src)
 int 
 AudioTrack::use_diskstream (string name)
 {
-	AudioDiskstream *dstream;
+	boost::shared_ptr<AudioDiskstream> dstream;
 
-	if ((dstream = dynamic_cast<AudioDiskstream*>(_session.diskstream_by_name (name))) == 0) {
-	  error << string_compose(_("AudioTrack: audio diskstream \"%1\" not known by session"), name) << endmsg;
+	if ((dstream = boost::dynamic_pointer_cast<AudioDiskstream>(_session.diskstream_by_name (name))) == 0) {
+		error << string_compose(_("AudioTrack: audio diskstream \"%1\" not known by session"), name) << endmsg;
 		return -1;
 	}
 	
-	return set_diskstream (*dstream, this);
+	return set_diskstream (dstream, this);
 }
 
 int 
 AudioTrack::use_diskstream (const PBD::ID& id)
 {
-	AudioDiskstream *dstream;
+	boost::shared_ptr<AudioDiskstream> dstream;
 
-	if ((dstream = dynamic_cast<AudioDiskstream*>(_session.diskstream_by_id (id))) == 0) {
+	if ((dstream = boost::dynamic_pointer_cast<AudioDiskstream> (_session.diskstream_by_id (id))) == 0) {
 	  	error << string_compose(_("AudioTrack: audio diskstream \"%1\" not known by session"), id) << endmsg;
 		return -1;
 	}
 	
-	return set_diskstream (*dstream, this);
+	return set_diskstream (dstream, this);
 }
 
-AudioDiskstream&
+boost::shared_ptr<AudioDiskstream>
 AudioTrack::audio_diskstream() const
 {
-	return *dynamic_cast<AudioDiskstream*>(_diskstream);
+	return boost::dynamic_pointer_cast<AudioDiskstream>(_diskstream);
 }
 
 int
@@ -434,7 +431,7 @@ AudioTrack::no_roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nf
 		return 0;
 	}
 
-	audio_diskstream().check_record_status (start_frame, nframes, can_record);
+	audio_diskstream()->check_record_status (start_frame, nframes, can_record);
 
 	bool send_silence;
 	
@@ -501,7 +498,7 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 	Sample* b;
 	Sample* tmpb;
 	jack_nframes_t transport_frame;
-	AudioDiskstream& diskstream = audio_diskstream();
+	boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 	
 	{
 		Glib::RWLock::ReaderLock lm (redirect_lock, Glib::TRY_LOCK);
@@ -528,13 +525,13 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 		   playback distance to zero, thus causing diskstream::commit
 		   to do nothing.
 		*/
-		return diskstream.process (transport_frame, 0, 0, can_record, rec_monitors_input);
+		return diskstream->process (transport_frame, 0, 0, can_record, rec_monitors_input);
 	} 
 
 	_silent = false;
 	apply_gain_automation = false;
 
-	if ((dret = diskstream.process (transport_frame, nframes, offset, can_record, rec_monitors_input)) != 0) {
+	if ((dret = diskstream->process (transport_frame, nframes, offset, can_record, rec_monitors_input)) != 0) {
 		
 		silence (nframes, offset);
 
@@ -547,7 +544,7 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 		just_meter_input (start_frame, end_frame, nframes, offset);
 	}
 
-	if (diskstream.record_enabled() && !can_record && !_session.get_auto_input()) {
+	if (diskstream->record_enabled() && !can_record && !_session.get_auto_input()) {
 
 		/* not actually recording, but we want to hear the input material anyway,
 		   at least potentially (depending on monitoring options)
@@ -555,7 +552,7 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 
 		passthru (start_frame, end_frame, nframes, offset, 0, true);
 
-	} else if ((b = diskstream.playback_buffer(0)) != 0) {
+	} else if ((b = diskstream->playback_buffer(0)) != 0) {
 
 		/*
 		  XXX is it true that the earlier test on n_outputs()
@@ -577,8 +574,8 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 
 		for (i = 0, n = 1; i < limit; ++i, ++n) {
 			memcpy (bufs[i], b, sizeof (Sample) * nframes); 
-			if (n < diskstream.n_channels()) {
-				tmpb = diskstream.playback_buffer(n);
+			if (n < diskstream->n_channels()) {
+				tmpb = diskstream->playback_buffer(n);
 				if (tmpb!=0) {
 					b = tmpb;
 				}
@@ -587,7 +584,7 @@ AudioTrack::roll (jack_nframes_t nframes, jack_nframes_t start_frame, jack_nfram
 
 		/* don't waste time with automation if we're recording or we've just stopped (yes it can happen) */
 
-		if (!diskstream.record_enabled() && _session.transport_rolling()) {
+		if (!diskstream->record_enabled() && _session.transport_rolling()) {
 			Glib::Mutex::Lock am (automation_lock, Glib::TRY_LOCK);
 			
 			if (am.locked() && gain_automation_playback()) {
@@ -623,7 +620,7 @@ AudioTrack::silent_roll (jack_nframes_t nframes, jack_nframes_t start_frame, jac
 
 	silence (nframes, offset);
 
-	return audio_diskstream().process (_session.transport_frame() + offset, nframes, offset, can_record, rec_monitors_input);
+	return audio_diskstream()->process (_session.transport_frame() + offset, nframes, offset, can_record, rec_monitors_input);
 }
 
 int
@@ -637,12 +634,12 @@ AudioTrack::export_stuff (vector<Sample*>& buffers, uint32_t nbufs, jack_nframes
 	gain_t this_gain = _gain;
 	vector<Sample*>::iterator bi;
 	Sample * b;
-	AudioDiskstream& diskstream = audio_diskstream();
+	boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 	
 	Glib::RWLock::ReaderLock rlock (redirect_lock);
 
 	// FIXME
-	AudioPlaylist* const apl = dynamic_cast<AudioPlaylist*>(diskstream.playlist());
+	AudioPlaylist* const apl = dynamic_cast<AudioPlaylist*>(diskstream->playlist());
 	assert(apl);
 
 	if (apl->read (buffers[0], mix_buffer, gain_buffer, start, nframes) != nframes) {
@@ -654,7 +651,7 @@ AudioTrack::export_stuff (vector<Sample*>& buffers, uint32_t nbufs, jack_nframes
 	b = buffers[0];
 	++bi;
 	for (; bi != buffers.end(); ++bi, ++n) {
-		if (n < diskstream.n_channels()) {
+		if (n < diskstream->n_channels()) {
 			if (apl->read ((*bi), mix_buffer, gain_buffer, start, nframes, n) != nframes) {
 				return -1;
 			}
@@ -751,9 +748,9 @@ AudioTrack::freeze (InterThreadInfo& itt)
 	string dir;
 	AudioRegion* region;
 	string region_name;
-	AudioDiskstream& diskstream = audio_diskstream();
+	boost::shared_ptr<AudioDiskstream> diskstream = audio_diskstream();
 	
-	if ((_freeze_record.playlist = dynamic_cast<AudioPlaylist*>(diskstream.playlist())) == 0) {
+	if ((_freeze_record.playlist = dynamic_cast<AudioPlaylist*>(diskstream->playlist())) == 0) {
 		return;
 	}
 
@@ -821,13 +818,13 @@ AudioTrack::freeze (InterThreadInfo& itt)
 				  (AudioRegion::Flag) (AudioRegion::WholeFile|AudioRegion::DefaultFlags),
 				  false);
 
-	new_playlist->set_orig_diskstream_id (diskstream.id());
+	new_playlist->set_orig_diskstream_id (diskstream->id());
 	new_playlist->add_region (*region, 0);
 	new_playlist->set_frozen (true);
 	region->set_locked (true);
 
-	diskstream.use_playlist (dynamic_cast<AudioPlaylist*>(new_playlist));
-	diskstream.set_record_enabled (false);
+	diskstream->use_playlist (dynamic_cast<AudioPlaylist*>(new_playlist));
+	diskstream->set_record_enabled (false);
 
 	_freeze_record.state = Frozen;
 	FreezeChange(); /* EMIT SIGNAL */
@@ -837,7 +834,7 @@ void
 AudioTrack::unfreeze ()
 {
 	if (_freeze_record.playlist) {
-		audio_diskstream().use_playlist (_freeze_record.playlist);
+		audio_diskstream()->use_playlist (_freeze_record.playlist);
 
 		if (_freeze_record.have_mementos) {
 
diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index 982a7c5971..4a4659d1df 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -47,6 +47,7 @@ jack_nframes_t Port::_short_over_length = 2;
 jack_nframes_t Port::_long_over_length = 10;
 
 AudioEngine::AudioEngine (string client_name) 
+	: ports (new Ports)
 {
 	session = 0;
 	session_remove_pending = false;
@@ -270,7 +271,10 @@ AudioEngine::process_callback (jack_nframes_t nframes)
 	}
 
 	if (last_monitor_check + monitor_check_interval < next_processed_frames) {
-		for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+
+		boost::shared_ptr<Ports> p = ports.reader();
+
+		for (Ports::iterator i = p->begin(); i != p->end(); ++i) {
 			
 			Port *port = (*i);
 			bool x;
@@ -329,7 +333,9 @@ AudioEngine::jack_bufsize_callback (jack_nframes_t nframes)
 	_usecs_per_cycle = (int) floor ((((double) nframes / frame_rate())) * 1000000.0);
 	last_monitor_check = 0;
 
-	for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+	boost::shared_ptr<Ports> p = ports.reader();
+
+	for (Ports::iterator i = p->begin(); i != p->end(); ++i) {
 		(*i)->reset();
 	}
 
@@ -400,15 +406,19 @@ AudioEngine::register_input_port (DataType type, const string& portname)
 		}
 	}
 
-	jack_port_t *p = jack_port_register (_jack, portname.c_str(),
-		type.to_jack_type(), JackPortIsInput, 0);
+	jack_port_t *p = jack_port_register (_jack, portname.c_str(), type.to_jack_type(), JackPortIsInput, 0);
 
 	if (p) {
 
 		Port *newport;
+
 		if ((newport = new Port (p)) != 0) {
-			ports.insert (ports.begin(), newport);
+			RCUWriter<Ports> writer (ports);
+			boost::shared_ptr<Ports> ps = writer.get_copy ();
+			ps->insert (ps->begin(), newport);
+			/* writer goes out of scope, forces update */
 		}
+
 		return newport;
 
 	} else {
@@ -436,8 +446,19 @@ AudioEngine::register_output_port (DataType type, const string& portname)
 
 	if ((p = jack_port_register (_jack, portname.c_str(),
 		type.to_jack_type(), JackPortIsOutput, 0)) != 0) {
-		Port *newport = new Port (p);
-		ports.insert (ports.begin(), newport);
+
+		Port *newport = 0;
+
+		{
+			RCUWriter<Ports> writer (ports);
+			boost::shared_ptr<Ports> ps = writer.get_copy ();
+			
+			newport = new Port (p);
+			ps->insert (ps->begin(), newport);
+
+			/* writer goes out of scope, forces update */
+		}
+
 		return newport;
 
 	} else {
@@ -465,12 +486,20 @@ AudioEngine::unregister_port (Port *port)
 		int ret = jack_port_unregister (_jack, port->_port);
 		
 		if (ret == 0) {
-
-			for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
-				if ((*i) == port) {
-					ports.erase (i);
-					break;
+			
+			{
+
+				RCUWriter<Ports> writer (ports);
+				boost::shared_ptr<Ports> ps = writer.get_copy ();
+				
+				for (Ports::iterator i = ps->begin(); i != ps->end(); ++i) {
+					if ((*i) == port) {
+						ps->erase (i);
+						break;
+					}
 				}
+
+				/* writer goes out of scope, forces update */
 			}
 
 			remove_connections_for (port);
@@ -613,7 +642,9 @@ AudioEngine::get_port_by_name (const string& portname, bool keep)
 	
 	/* check to see if we have a Port for this name already */
 
-	for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+	boost::shared_ptr<Ports> pr = ports.reader();
+	
+	for (Ports::iterator i = pr->begin(); i != pr->end(); ++i) {
 		if (portname == (*i)->name()) {
 			return (*i);
 		}
@@ -623,11 +654,20 @@ AudioEngine::get_port_by_name (const string& portname, bool keep)
 
 	if ((p = jack_port_by_name (_jack, portname.c_str())) != 0) {
 		Port *newport = new Port (p);
-		if (keep && newport->is_mine (_jack)) {
-			ports.insert (newport);
+
+		{
+			if (keep && newport->is_mine (_jack)) {
+				RCUWriter<Ports> writer (ports);
+				boost::shared_ptr<Ports> ps = writer.get_copy ();
+				ps->insert (newport);
+				/* writer goes out of scope, forces update */
+			}
 		}
+
 		return newport;
+
 	} else {
+
 		return 0;
 	}
 }
@@ -827,12 +867,19 @@ AudioEngine::remove_all_ports ()
 	/* process lock MUST be held */
 
 	if (_jack) {
-		for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+		boost::shared_ptr<Ports> p = ports.reader();
+
+		for (Ports::iterator i = p->begin(); i != p->end(); ++i) {
 			jack_port_unregister (_jack, (*i)->_port);
 		}
 	}
 
-	ports.clear ();
+	{
+		RCUWriter<Ports> writer (ports);
+		boost::shared_ptr<Ports> ps = writer.get_copy ();
+		ps->clear ();
+	}
+
 	port_connections.clear ();
 }
 
@@ -932,7 +979,7 @@ AudioEngine::reconnect_to_jack ()
 	if (_jack) {
 		disconnect_from_jack ();
 		/* XXX give jackd a chance */
-        Glib::usleep (250000);
+		Glib::usleep (250000);
 	}
 
 	if (connect_to_jack (jack_client_name)) {
@@ -942,7 +989,9 @@ AudioEngine::reconnect_to_jack ()
 
 	Ports::iterator i;
 
-	for (i = ports.begin(); i != ports.end(); ++i) {
+	boost::shared_ptr<Ports> p = ports.reader ();
+
+	for (i = p->begin(); i != p->end(); ++i) {
 
 		/* XXX hack hack hack */
 
@@ -964,8 +1013,9 @@ AudioEngine::reconnect_to_jack ()
 		}
 	}
 
-	if (i != ports.end()) {
-		for (Ports::iterator i = ports.begin(); i != ports.end(); ++i) {
+	if (i != p->end()) {
+		/* failed */
+		for (Ports::iterator i = p->begin(); i != p->end(); ++i) {
 			jack_port_unregister (_jack, (*i)->_port);
 		}
 		return -1;
diff --git a/libs/ardour/auditioner.cc b/libs/ardour/auditioner.cc
index e48f103b9f..dc08979458 100644
--- a/libs/ardour/auditioner.cc
+++ b/libs/ardour/auditioner.cc
@@ -49,7 +49,7 @@ Auditioner::Auditioner (Session& s)
 	}
 
 	if (right.length()) {
-		audio_diskstream().add_channel();
+		audio_diskstream()->add_channel();
 		add_output_port (right, this, DataType::AUDIO);
 	}
 
@@ -117,11 +117,11 @@ Auditioner::audition_region (AudioRegion& region)
 	_diskstream->playlist()->add_region (*the_region, 0, 1, false);
 
 	while (_diskstream->n_channels() < the_region->n_channels()) {
-		audio_diskstream().add_channel ();
+		audio_diskstream()->add_channel ();
 	}
 
 	while (_diskstream->n_channels() > the_region->n_channels()) {
-		audio_diskstream().remove_channel ();
+		audio_diskstream()->remove_channel ();
 	}
 
 	/* force a panner reset now that we have all channels */
diff --git a/libs/ardour/diskstream.cc b/libs/ardour/diskstream.cc
index b2d481077f..151ff5bd3e 100644
--- a/libs/ardour/diskstream.cc
+++ b/libs/ardour/diskstream.cc
@@ -63,7 +63,6 @@ using namespace PBD;
  */
 jack_nframes_t Diskstream::disk_io_chunk_frames = 1024 * 256;
 
-sigc::signal<void,Diskstream*>    Diskstream::DiskstreamCreated;
 sigc::signal<void,list<Source*>*> Diskstream::DeleteSources;
 sigc::signal<void>                Diskstream::DiskOverrun;
 sigc::signal<void>                Diskstream::DiskUnderrun;
@@ -86,7 +85,6 @@ Diskstream::Diskstream (Session& sess, const XMLNode& node)
 void
 Diskstream::init (Flag f)
 {
-	_refcnt = 0;
 	_flags = f;
 	_io = 0;
 	_alignment_style = ExistingMaterial;
diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index b47981a47e..02c62eefa1 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -111,7 +111,8 @@ Route::init ()
 
 Route::~Route ()
 {
-	GoingAway (); /* EMIT SIGNAL */
+	cerr << "deleting route " << _name << endl;
+
 	clear_redirects (this);
 
 	if (_control_outs) {
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 48f7fc30e9..378d4763bc 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -256,6 +256,7 @@ Session::Session (AudioEngine &eng,
 	  _midi_port (default_midi_port),
 	  pending_events (2048),
 	  midi_requests (128), // the size of this should match the midi request pool size
+	  diskstreams (new DiskstreamList),
 	  routes (new RouteList),
 	  auditioner ((Auditioner*) 0),
 	  _click_io ((IO*) 0),
@@ -306,6 +307,7 @@ Session::Session (AudioEngine &eng,
 	  _midi_port (default_midi_port),
 	  pending_events (2048),
 	  midi_requests (16),
+	  diskstreams (new DiskstreamList),
 	  routes (new RouteList),
 	  main_outs (0)
 
@@ -439,18 +441,45 @@ Session::~Session ()
 	}
 	
 #ifdef TRACK_DESTRUCTION
-	cerr << "delete diskstreams\n";
+	cerr << "delete routes\n";
 #endif /* TRACK_DESTRUCTION */
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ) {
-		DiskstreamList::iterator tmp;
-
-		tmp = i;
-		++tmp;
+        {
+		RCUWriter<RouteList> writer (routes);
+		boost::shared_ptr<RouteList> r = writer.get_copy ();
+		for (RouteList::iterator i = r->begin(); i != r->end(); ) {
+			RouteList::iterator tmp;
+			tmp = i;
+			++tmp;
+			cerr << "BEFORE: use count on route " << (*i)->name() << " = " << (*i).use_count() << endl;
+			(*i)->drop_references ();
+			cerr << "AFTER: use count on route " << (*i)->name() << " = " << (*i).use_count() << endl;
+			i = tmp;
+		}
+		r->clear ();
+		/* writer goes out of scope and updates master */
+	}
 
-		delete *i;
+	routes.flush ();
 
-		i = tmp;
-	}
+#ifdef TRACK_DESTRUCTION
+	cerr << "delete diskstreams\n";
+#endif /* TRACK_DESTRUCTION */
+       {
+	       RCUWriter<DiskstreamList> dwriter (diskstreams);
+	       boost::shared_ptr<DiskstreamList> dsl = dwriter.get_copy();
+	       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ) {
+		       DiskstreamList::iterator tmp;
+		       
+		       tmp = i;
+		       ++tmp;
+		       
+		       (*i)->drop_references ();
+		       
+		       i = tmp;
+	       }
+	       dsl->clear ();
+       }
+       diskstreams.flush ();
 
 #ifdef TRACK_DESTRUCTION
 	cerr << "delete audio sources\n";
@@ -859,7 +888,7 @@ Session::playlist_length_changed (Playlist* pl)
 }
 
 void
-Session::diskstream_playlist_changed (Diskstream* dstream)
+Session::diskstream_playlist_changed (boost::shared_ptr<Diskstream> dstream)
 {
 	Playlist *playlist;
 
@@ -933,13 +962,10 @@ Session::set_auto_input (bool yn)
 		
 		if (Config->get_use_hardware_monitoring() && transport_rolling()) {
 			/* auto-input only makes a difference if we're rolling */
+			
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-			/* Even though this can called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					//cerr << "switching to input = " << !auto_input << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (!auto_input);   
@@ -956,16 +982,19 @@ void
 Session::reset_input_monitor_state ()
 {
 	if (transport_rolling()) {
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if ((*i)->record_enabled ()) {
 				//cerr << "switching to input = " << !auto_input << __FILE__ << __LINE__ << endl << endl;
 				(*i)->monitor_input (Config->get_use_hardware_monitoring() && !auto_input);
 			}
 		}
 	} else {
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if ((*i)->record_enabled ()) {
 				//cerr << "switching to input = " << !auto_input << __FILE__ << __LINE__ << endl << endl;
 				(*i)->monitor_input (Config->get_use_hardware_monitoring());
@@ -1237,13 +1266,8 @@ Session::enable_record ()
 		send_mmc_in_another_thread (MIDI::MachineControl::cmdRecordStrobe);
 
 		if (Config->get_use_hardware_monitoring() && auto_input) {
-			/* Even though this can be called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					(*i)->monitor_input (true);   
 				}
@@ -1272,13 +1296,9 @@ Session::disable_record (bool rt_context, bool force)
 		send_mmc_in_another_thread (MIDI::MachineControl::cmdRecordExit);
 
 		if (Config->get_use_hardware_monitoring() && auto_input) {
-			/* Even though this can be called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 			
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					(*i)->monitor_input (false);   
 				}
@@ -1299,13 +1319,9 @@ Session::step_back_from_record ()
 	g_atomic_int_set (&_record_status, Enabled);
 
 	if (Config->get_use_hardware_monitoring()) {
-		/* Even though this can be called from RT context we are using
-		   a non-tentative rwlock here,  because the action must occur.
-		   The rarity and short potential lock duration makes this "OK"
-		*/
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 		
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		        if (auto_input && (*i)->record_enabled ()) {
 			        //cerr << "switching from input" << __FILE__ << __LINE__ << endl << endl;
 		                (*i)->monitor_input (false);   
@@ -1428,7 +1444,6 @@ Session::set_block_size (jack_nframes_t nframes)
 	*/
 
 	{ 
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
 		vector<Sample*>::iterator i;
 		uint32_t np;
 			
@@ -1475,7 +1490,8 @@ Session::set_block_size (jack_nframes_t nframes)
 			(*i)->set_block_size (nframes);
 		}
 		
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			(*i)->set_block_size (nframes);
 		}
 
@@ -1863,7 +1879,7 @@ Session::new_audio_route (int input_channels, int output_channels)
 }
 
 void
-Session::add_route (shared_ptr<Route> route)
+Session::add_route (boost::shared_ptr<Route> route)
 {
 	{ 
 		RCUWriter<RouteList> writer (routes);
@@ -1892,22 +1908,17 @@ Session::add_route (shared_ptr<Route> route)
 }
 
 void
-Session::add_diskstream (Diskstream* dstream)
+Session::add_diskstream (boost::shared_ptr<Diskstream> dstream)
 {
 	/* need to do this in case we're rolling at the time, to prevent false underruns */
 	dstream->do_refill_with_alloc();
 	
 	{ 
-		Glib::RWLock::WriterLock lm (diskstream_lock);
-		diskstreams.push_back (dstream);
+		RCUWriter<DiskstreamList> writer (diskstreams);
+		boost::shared_ptr<DiskstreamList> ds = writer.get_copy();
+		ds->push_back (dstream);
 	}
 
-	/* take a reference to the diskstream, preventing it from
-	   ever being deleted until the session itself goes away,
-	   or chooses to remove it for its own purposes.
-	*/
-
-	dstream->ref();
 	dstream->set_block_size (current_block_size);
 
 	dstream->PlaylistChanged.connect (sigc::bind (mem_fun (*this, &Session::diskstream_playlist_changed), dstream));
@@ -1918,8 +1929,6 @@ Session::add_diskstream (Diskstream* dstream)
 
 	set_dirty();
 	save_state (_current_snapshot_name);
-
-	DiskstreamAdded (dstream); /* EMIT SIGNAL */
 }
 
 void
@@ -1958,20 +1967,19 @@ Session::remove_route (shared_ptr<Route> route)
 
 	// FIXME: audio specific
 	AudioTrack* at;
-	AudioDiskstream* ds = 0;
+	boost::shared_ptr<AudioDiskstream> ds;
 	
 	if ((at = dynamic_cast<AudioTrack*>(route.get())) != 0) {
-		ds = &at->audio_diskstream();
+		ds = at->audio_diskstream();
 	}
 	
 	if (ds) {
 
 		{
-			Glib::RWLock::WriterLock lm (diskstream_lock);
-			diskstreams.remove (ds);
+			RCUWriter<DiskstreamList> dsl (diskstreams);
+			boost::shared_ptr<DiskstreamList> d = dsl.get_copy();
+			d->remove (ds);
 		}
-
-		ds->unref ();
 	}
 
 	find_current_end ();
@@ -1983,7 +1991,9 @@ Session::remove_route (shared_ptr<Route> route)
 
 	save_state (_current_snapshot_name);
 
-	/* all shared ptrs to route should go out of scope here */
+	/* try to cause everyone to drop their references */
+
+	route->drop_references ();
 }	
 
 void
@@ -2271,11 +2281,9 @@ Session::get_maximum_extent () const
 	jack_nframes_t max = 0;
 	jack_nframes_t me; 
 
-	/* Don't take the diskstream lock. Caller must have other ways to
-	   ensure atomicity.
-	*/
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::const_iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::const_iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		Playlist* pl = (*i)->playlist();
 		if ((me = pl->get_maximum_extent()) > max) {
 			max = me;
@@ -2285,32 +2293,32 @@ Session::get_maximum_extent () const
 	return max;
 }
 
-Diskstream *
+boost::shared_ptr<Diskstream>
 Session::diskstream_by_name (string name)
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if ((*i)->name() == name) {
-			return* i;
+			return *i;
 		}
 	}
 
-	return 0;
+	return boost::shared_ptr<Diskstream>((Diskstream*) 0);
 }
 
-Diskstream *
+boost::shared_ptr<Diskstream>
 Session::diskstream_by_id (const PBD::ID& id)
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if ((*i)->id() == id) {
 			return *i;
 		}
 	}
 
-	return 0;
+	return boost::shared_ptr<Diskstream>((Diskstream*) 0);
 }
 
 /* AudioRegion management */
@@ -2621,10 +2629,10 @@ int
 Session::remove_last_capture ()
 {
 	list<Region*> r;
-
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		list<Region*>& l = (*i)->last_capture_regions();
 		
 		if (!l.empty()) {
@@ -3185,10 +3193,11 @@ Session::set_all_mute (bool yn)
 uint32_t
 Session::n_diskstreams () const
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
 	uint32_t n = 0;
 
-	for (DiskstreamList::const_iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+	for (DiskstreamList::const_iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if (!(*i)->hidden()) {
 			n++;
 		}
@@ -3207,15 +3216,15 @@ Session::graph_reordered ()
 		return;
 	}
 
-	Glib::RWLock::ReaderLock lm2 (diskstream_lock);
-
 	resort_routes ();
 
 	/* force all diskstreams to update their capture offset values to 
 	   reflect any changes in latencies within the graph.
 	*/
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->set_capture_offset ();
 	}
 }
@@ -3494,11 +3503,9 @@ Session::remove_named_selection (NamedSelection* named_selection)
 void
 Session::reset_native_file_format ()
 {
-	// jlc - WHY take routelock?
-	//RWLockMonitor lm1 (route_lock, true, __LINE__, __FILE__);
-	Glib::RWLock::ReaderLock lm2 (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->reset_write_sources (false);
 	}
 }
@@ -3608,7 +3615,7 @@ Session::write_one_audio_track (AudioTrack& track, jack_nframes_t start, jack_nf
 	
 	/* call tree *MUST* hold route_lock */
 	
-	if ((playlist = track.diskstream().playlist()) == 0) {
+	if ((playlist = track.diskstream()->playlist()) == 0) {
 		goto out;
 	}
 
@@ -3618,7 +3625,7 @@ Session::write_one_audio_track (AudioTrack& track, jack_nframes_t start, jack_nf
 		goto out;
 	}
 
-	nchans = track.audio_diskstream().n_channels();
+	nchans = track.audio_diskstream()->n_channels();
 	
 	dir = discover_best_sound_dir ();
 
diff --git a/libs/ardour/session_butler.cc b/libs/ardour/session_butler.cc
index 6509a783bb..5d691a7425 100644
--- a/libs/ardour/session_butler.cc
+++ b/libs/ardour/session_butler.cc
@@ -248,11 +248,11 @@ Session::butler_thread_work ()
 
 		gettimeofday (&begin, 0);
 
-		Glib::RWLock::ReaderLock dsm (diskstream_lock);
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader ();
 		
-		for (i = diskstreams.begin(); !transport_work_requested() && butler_should_run && i != diskstreams.end(); ++i) {
+		for (i = dsl->begin(); !transport_work_requested() && butler_should_run && i != dsl->end(); ++i) {
 
-			Diskstream* const ds = *i;
+			boost::shared_ptr<Diskstream> ds = *i;
 
 			switch (ds->do_refill ()) {
 			case 0:
@@ -271,7 +271,7 @@ Session::butler_thread_work ()
 
 		}
 
-		if (i != diskstreams.end()) {
+		if (i != dsl->end()) {
 			/* we didn't get to all the streams */
 			disk_work_outstanding = true;
 		}
@@ -293,7 +293,7 @@ Session::butler_thread_work ()
 		compute_io = true;
 		gettimeofday (&begin, 0);
 
-		for (i = diskstreams.begin(); !transport_work_requested() && butler_should_run && i != diskstreams.end(); ++i) {
+		for (i = dsl->begin(); !transport_work_requested() && butler_should_run && i != dsl->end(); ++i) {
 			// cerr << "write behind for " << (*i)->name () << endl;
 			
 			switch ((*i)->do_flush (Session::ButlerContext)) {
@@ -322,7 +322,7 @@ Session::butler_thread_work ()
 			request_stop ();
 		}
 
-		if (i != diskstreams.end()) {
+		if (i != dsl->end()) {
 			/* we didn't get to all the streams */
 			disk_work_outstanding = true;
 		}
@@ -349,7 +349,7 @@ Session::butler_thread_work ()
 			Glib::Mutex::Lock lm (butler_request_lock);
 
 			if (butler_should_run && (disk_work_outstanding || transport_work_requested())) {
-//				for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+//				for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 //					cerr << "AFTER " << (*i)->name() << ": pb = " << (*i)->playback_buffer_load() << " cp = " << (*i)->capture_buffer_load() << endl;
 //				}
 
@@ -388,8 +388,8 @@ Session::overwrite_some_buffers (Diskstream* ds)
 
 	} else {
 
-		Glib::RWLock::ReaderLock dm (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			(*i)->set_pending_overwrite (true);
 		}
 	}
diff --git a/libs/ardour/session_export.cc b/libs/ardour/session_export.cc
index b39c4f2218..98653314b0 100644
--- a/libs/ardour/session_export.cc
+++ b/libs/ardour/session_export.cc
@@ -495,8 +495,9 @@ Session::prepare_to_export (AudioExportSpecification& spec)
 	/* get everyone to the right position */
 
 	{
-		Glib::RWLock::ReaderLock lm (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if ((*i)-> seek (spec.start_frame, true)) {
 				error << string_compose (_("%1: cannot seek to %2 for export"),
 						  (*i)->name(), spec.start_frame)
diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index 88b111a1fb..68ad11cf42 100644
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -66,7 +66,8 @@ Session::process (jack_nframes_t nframes)
 void
 Session::prepare_diskstreams ()
 {
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->prepare ();
 	}
 }
@@ -141,7 +142,8 @@ Session::process_routes (jack_nframes_t nframes, jack_nframes_t offset)
 			   call path, so make sure we release any outstanding locks here before we return failure.
 			*/
 
-			for (DiskstreamList::iterator ids = diskstreams.begin(); ids != diskstreams.end(); ++ids) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+			for (DiskstreamList::iterator ids = dsl->begin(); ids != dsl->end(); ++ids) {
 				(*ids)->recover ();
 			}
 
@@ -181,7 +183,8 @@ Session::silent_process_routes (jack_nframes_t nframes, jack_nframes_t offset)
 			   call path, so make sure we release any outstanding locks here before we return failure.
 			*/
 
-			for (DiskstreamList::iterator ids = diskstreams.begin(); ids != diskstreams.end(); ++ids) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+			for (DiskstreamList::iterator ids = dsl->begin(); ids != dsl->end(); ++ids) {
 				(*ids)->recover ();
 			}
 
@@ -200,7 +203,8 @@ Session::commit_diskstreams (jack_nframes_t nframes, bool &needs_butler)
 	float pworst = 1.0f;
 	float cworst = 1.0f;
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 
 		if ((*i)->hidden()) {
 			continue;
@@ -284,12 +288,10 @@ Session::process_with_events (jack_nframes_t nframes)
 	end_frame = _transport_frame + nframes;
 
 	{
-		Glib::RWLock::ReaderLock dsm (diskstream_lock, Glib::TRY_LOCK);
-	
 		Event* this_event;
 		Events::iterator the_next_one;
 		
-		if (!dsm.locked() || (post_transport_work & (PostTransportLocate|PostTransportStop))) {
+		if (post_transport_work & (PostTransportLocate|PostTransportStop)) {
 			no_roll (nframes, 0);
 			return;
 		}
@@ -560,17 +562,18 @@ Session::follow_slave (jack_nframes_t nframes, jack_nframes_t offset)
 		if (slave_state == Waiting) {
 
 			// cerr << "waiting at " << slave_transport_frame << endl;
-			Glib::RWLock::ReaderLock dsm (diskstream_lock, Glib::TRY_LOCK);
-				
-			if (dsm.locked() && slave_transport_frame >= slave_wait_end) {
+			
+			if (slave_transport_frame >= slave_wait_end) {
 				// cerr << "\tstart at " << _transport_frame << endl;
 
 				slave_state = Running;
 
 				bool ok = true;
 				jack_nframes_t frame_delta = slave_transport_frame - _transport_frame;
+
+				boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 				
-				for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+				for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 					if (!(*i)->can_internal_playback_seek (frame_delta)) {
 						ok = false;
 						break;
@@ -578,7 +581,7 @@ Session::follow_slave (jack_nframes_t nframes, jack_nframes_t offset)
 				}
 
 				if (ok) {
-					for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+					for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 						(*i)->internal_playback_seek (frame_delta);
 					}
 					_transport_frame += frame_delta;
@@ -682,12 +685,6 @@ Session::follow_slave (jack_nframes_t nframes, jack_nframes_t offset)
 
 		bool need_butler;
 		
-		Glib::RWLock::ReaderLock dsm (diskstream_lock, Glib::TRY_LOCK);
-		if (!dsm.locked()) {
-			goto noroll;
-		}
-
-		
 		prepare_diskstreams ();
 		silent_process_routes (nframes, offset);
 		commit_diskstreams (nframes, need_butler);
@@ -733,9 +730,7 @@ Session::process_without_events (jack_nframes_t nframes)
 	long frames_moved;
 	
 	{
-		Glib::RWLock::ReaderLock dsm (diskstream_lock, Glib::TRY_LOCK);
-
-		if (!dsm.locked() || (post_transport_work & (PostTransportLocate|PostTransportStop))) {
+		if (post_transport_work & (PostTransportLocate|PostTransportStop)) {
 			no_roll (nframes, 0);
 			return;
 		}
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index 5a75c04b3f..6770428c65 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -264,7 +264,6 @@ Session::first_stage_init (string fullpath, string snapshot_name)
 	AudioSource::AudioSourceCreated.connect (mem_fun (*this, &Session::add_audio_source));
 	Playlist::PlaylistCreated.connect (mem_fun (*this, &Session::add_playlist));
 	Redirect::RedirectCreated.connect (mem_fun (*this, &Session::add_redirect));
-	AudioDiskstream::DiskstreamCreated.connect (mem_fun (*this, &Session::add_diskstream));
 	NamedSelection::NamedSelectionCreated.connect (mem_fun (*this, &Session::add_named_selection));
         Curve::CurveCreated.connect (mem_fun (*this, &Session::add_curve));
         AutomationList::AutomationListCreated.connect (mem_fun (*this, &Session::add_automation_list));
@@ -626,11 +625,10 @@ Session::load_diskstreams (const XMLNode& node)
 
 	for (citer = clist.begin(); citer != clist.end(); ++citer) {
 		
-		AudioDiskstream* dstream;
 
 		try {
-			dstream = new AudioDiskstream (*this, **citer);
-			/* added automatically by AudioDiskstreamCreated handler */
+			boost::shared_ptr<AudioDiskstream> dstream (new AudioDiskstream (*this, **citer));
+			add_diskstream (dstream);
 		} 
 		
 		catch (failed_constructor& err) {
@@ -1388,8 +1386,8 @@ Session::state(bool full_state)
 	child = node->add_child ("DiskStreams");
 
 	{ 
-		Glib::RWLock::ReaderLock dl (diskstream_lock);
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if (!(*i)->hidden()) {
 				child->add_child_nocopy ((*i)->get_state());
 			}
diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index 7c2b4f1c6f..8e0522c19d 100644
--- a/libs/ardour/session_transport.cc
+++ b/libs/ardour/session_transport.cc
@@ -192,8 +192,8 @@ Session::realtime_stop (bool abort)
 void
 Session::butler_transport_work ()
 {
-	Glib::RWLock::ReaderLock dsm (diskstream_lock);
 	boost::shared_ptr<RouteList> r = routes.reader ();
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
 	if (post_transport_work & PostTransportCurveRealloc) {
 		for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
@@ -202,7 +202,7 @@ Session::butler_transport_work ()
 	}
 
 	if (post_transport_work & PostTransportInputChange) {
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			(*i)->non_realtime_input_change ();
 		}
 	}
@@ -218,7 +218,7 @@ Session::butler_transport_work ()
 		cumulative_rf_motion = 0;
 		reset_rf_scale (0);
 
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if (!(*i)->hidden()) {
 				if ((*i)->speed() != 1.0f || (*i)->speed() != -1.0f) {
 					(*i)->seek ((jack_nframes_t) (_transport_frame * (double) (*i)->speed()));
@@ -248,9 +248,9 @@ Session::butler_transport_work ()
 void
 Session::non_realtime_set_speed ()
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->non_realtime_set_speed ();
 	}
 }
@@ -258,9 +258,9 @@ Session::non_realtime_set_speed ()
 void
 Session::non_realtime_overwrite ()
 {
-	Glib::RWLock::ReaderLock lm (diskstream_lock);
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if ((*i)->pending_overwrite) {
 			(*i)->overwrite_existing_buffers ();
 		}
@@ -276,7 +276,9 @@ Session::non_realtime_stop (bool abort)
 	
 	did_record = false;
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if ((*i)->get_captured_frames () != 0) {
 			did_record = true;
 			break;
@@ -331,7 +333,7 @@ Session::non_realtime_stop (bool abort)
 		_have_captured = true;
 	}
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->transport_stopped (*now, xnow, abort);
 	}
 	
@@ -370,7 +372,7 @@ Session::non_realtime_stop (bool abort)
 	}
 #endif
 
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if (!(*i)->hidden()) {
 				if ((*i)->speed() != 1.0f || (*i)->speed() != -1.0f) {
 					(*i)->seek ((jack_nframes_t) (_transport_frame * (double) (*i)->speed()));
@@ -497,7 +499,8 @@ Session::set_auto_loop (bool yn)
 
 			if (seamless_loop) {
 				// set all diskstreams to use internal looping
-				for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+				boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+				for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 					if (!(*i)->hidden()) {
 						(*i)->set_loop (loc);
 					}
@@ -505,7 +508,8 @@ Session::set_auto_loop (bool yn)
 			}
 			else {
 				// set all diskstreams to NOT use internal looping
-				for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+				boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+				for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 					if (!(*i)->hidden()) {
 						(*i)->set_loop (0);
 					}
@@ -535,7 +539,8 @@ Session::set_auto_loop (bool yn)
 		clear_events (Event::AutoLoop);
 
 		// set all diskstreams to NOT use internal looping
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if (!(*i)->hidden()) {
 				(*i)->set_loop (0);
 			}
@@ -648,12 +653,10 @@ Session::locate (jack_nframes_t target_frame, bool with_roll, bool with_flush, b
 	if (with_roll) {
 		/* switch from input if we're going to roll */
 		if (Config->get_use_hardware_monitoring()) {
-			/* Even though this is called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					//cerr << "switching from input" << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (!auto_input);
@@ -663,12 +666,9 @@ Session::locate (jack_nframes_t target_frame, bool with_roll, bool with_flush, b
 	} else {
 		/* otherwise we're going to stop, so do the opposite */
 		if (Config->get_use_hardware_monitoring()) {
-			/* Even though this is called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					//cerr << "switching to input" << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (true);
@@ -707,12 +707,9 @@ Session::set_transport_speed (float speed, bool abort)
 
 		if (Config->get_use_hardware_monitoring())
 		{
-			/* Even though this is called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if ((*i)->record_enabled ()) {
 					//cerr << "switching to input" << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (true);	
@@ -733,12 +730,10 @@ Session::set_transport_speed (float speed, bool abort)
 		}
 
 		if (Config->get_use_hardware_monitoring()) {
-			/* Even though this is called from RT context we are using
-			   a non-tentative rwlock here,  because the action must occur.
-			   The rarity and short potential lock duration makes this "OK"
-			*/
-			Glib::RWLock::ReaderLock dsm (diskstream_lock);
-			for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+
+			boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+			for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 				if (auto_input && (*i)->record_enabled ()) {
 					//cerr << "switching from input" << __FILE__ << __LINE__ << endl << endl;
 					(*i)->monitor_input (false);	
@@ -789,7 +784,8 @@ Session::set_transport_speed (float speed, bool abort)
 		_last_transport_speed = _transport_speed;
 		_transport_speed = speed;
 		
-		for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+		boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+		for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 			if ((*i)->realtime_set_speed ((*i)->speed(), true)) {
 				post_transport_work = PostTransportWork (post_transport_work | PostTransportSpeed);
 			}
@@ -879,7 +875,8 @@ Session::actually_start_transport ()
 	transport_sub_state |= PendingDeclickIn;
 	_transport_speed = 1.0;
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->realtime_set_speed ((*i)->speed(), true);
 	}
 
@@ -1009,7 +1006,8 @@ Session::set_slave_source (SlaveSource src, jack_nframes_t frame)
 	
 	_slave_type = src;
 
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		if (!(*i)->hidden()) {
 			if ((*i)->realtime_set_speed ((*i)->speed(), true)) {
 				non_rt_required = true;
@@ -1200,7 +1198,6 @@ Session::update_latency_compensation (bool with_stop, bool abort)
 		return;
 	}
 
-	Glib::RWLock::ReaderLock lm2 (diskstream_lock);
 	_worst_track_latency = 0;
 
 	boost::shared_ptr<RouteList> r = routes.reader ();
@@ -1238,7 +1235,9 @@ Session::update_latency_compensation (bool with_stop, bool abort)
 	/* reflect any changes in latencies into capture offsets
 	*/
 	
-	for (DiskstreamList::iterator i = diskstreams.begin(); i != diskstreams.end(); ++i) {
+	boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+
+	for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
 		(*i)->set_capture_offset ();
 	}
 }
diff --git a/libs/ardour/track.cc b/libs/ardour/track.cc
index 58d8c1b306..c8633d9e52 100644
--- a/libs/ardour/track.cc
+++ b/libs/ardour/track.cc
@@ -41,7 +41,6 @@ using namespace PBD;
 
 Track::Track (Session& sess, string name, Route::Flag flag, TrackMode mode, DataType default_type)
 	: Route (sess, name, 1, -1, -1, -1, flag, default_type)
-	, _diskstream (0)
 	,  _rec_enable_control (*this)
 {
 	_declickable = true;
@@ -52,7 +51,6 @@ Track::Track (Session& sess, string name, Route::Flag flag, TrackMode mode, Data
 
 Track::Track (Session& sess, const XMLNode& node, DataType default_type)
 	: Route (sess, "to be renamed", 0, 0, -1, -1, Route::Flag(0), default_type)
-	, _diskstream (0)
 	, _rec_enable_control (*this)
 {
 	_freeze_record.state = NoFreeze;
@@ -62,9 +60,6 @@ Track::Track (Session& sess, const XMLNode& node, DataType default_type)
 
 Track::~Track ()
 {
-	if (_diskstream) {
-		_diskstream->unref();
-	}
 }
 
 void