fix (?) tricky locking issues in the tempo map by adding a second lock and independently locking the metrics and the map itself

git-svn-id: svn://localhost/ardour2/branches/3.0@11157 d708f5d6-7413-0410-9779-e7cbd77b26cf

2 files changed, 156 insertions, 119 deletions

diff --git a/libs/ardour/ardour/tempo.h b/libs/ardour/ardour/tempo.h
index 3f4b783de7..f0a63be05f 100644
--- a/libs/ardour/ardour/tempo.h
+++ b/libs/ardour/ardour/tempo.h
@@ -223,16 +223,14 @@ class TempoMap : public PBD::StatefulDestructible
 	typedef std::vector<BBTPoint> BBTPointList;
 
 	template<class T> void apply_with_metrics (T& obj, void (T::*method)(const Metrics&)) {
-		Glib::RWLock::ReaderLock lm (lock);
+		Glib::RWLock::ReaderLock lm (metrics_lock);
 		(obj.*method)(*metrics);
 	}
 
-	const BBTPointList& map() const { return _map ; }
-
 	void map (BBTPointList::const_iterator&, BBTPointList::const_iterator&, 
 		  framepos_t start, framepos_t end);
 	
-	void      bbt_time (framepos_t when, Timecode::BBT_Time&);
+	void       bbt_time (framepos_t when, Timecode::BBT_Time&);
         framecnt_t frame_time (const Timecode::BBT_Time&);
 	framecnt_t bbt_duration_at (framepos_t, const Timecode::BBT_Time&, int dir);
 
@@ -299,31 +297,32 @@ class TempoMap : public PBD::StatefulDestructible
 	framepos_t           last_bbt_when;
 	bool                 last_bbt_valid;
 	Timecode::BBT_Time   last_bbt;
-	mutable Glib::RWLock lock;
-	BBTPointList          _map;
+	mutable Glib::RWLock metrics_lock;
+	mutable Glib::RWLock map_lock;
+	BBTPointList*       _map;
 
 	void recompute_map (bool reassign_tempo_bbt, framepos_t end = -1);
         void require_map_to (framepos_t pos);
         void require_map_to (const Timecode::BBT_Time&);
 
-    BBTPointList::const_iterator bbt_before_or_at (framepos_t);
-    BBTPointList::const_iterator bbt_after_or_at (framepos_t);
-    BBTPointList::const_iterator bbt_point_for (const Timecode::BBT_Time&);
-
+	BBTPointList::const_iterator bbt_before_or_at (framepos_t);
+	BBTPointList::const_iterator bbt_after_or_at (framepos_t);
+	BBTPointList::const_iterator bbt_point_for (const Timecode::BBT_Time&);
+	
 	void timestamp_metrics_from_audio_time ();
-
+	
 	framepos_t round_to_type (framepos_t fr, int dir, BBTPointType);
-
+	
         void bbt_time_unlocked (framepos_t, Timecode::BBT_Time&, const BBTPointList::const_iterator&);
-
-    framecnt_t bbt_duration_at_unlocked (const Timecode::BBT_Time& when, const Timecode::BBT_Time& bbt, int dir);
-
+	
+	framecnt_t bbt_duration_at_unlocked (const Timecode::BBT_Time& when, const Timecode::BBT_Time& bbt, int dir);
+	
 	const MeterSection& first_meter() const;
 	const TempoSection& first_tempo() const;
-
+	
 	int move_metric_section (MetricSection&, const Timecode::BBT_Time& to);
 	void do_insert (MetricSection* section);
-
+	
 	Timecode::BBT_Time bbt_add (const Timecode::BBT_Time&, const Timecode::BBT_Time&, const TempoMetric&) const;
 	Timecode::BBT_Time bbt_add (const Timecode::BBT_Time& a, const Timecode::BBT_Time& b) const;
 	Timecode::BBT_Time bbt_subtract (const Timecode::BBT_Time&, const Timecode::BBT_Time&) const;
diff --git a/libs/ardour/tempo.cc b/libs/ardour/tempo.cc
index 54bb23d517..e8f894c1b4 100644
--- a/libs/ardour/tempo.cc
+++ b/libs/ardour/tempo.cc
@@ -278,6 +278,7 @@ struct MetricSectionSorter {
 TempoMap::TempoMap (framecnt_t fr)
 {
 	metrics = new Metrics;
+	_map = new BBTPointList;
 	_frame_rate = fr;
 	last_bbt_valid = false;
 	BBT_Time start;
@@ -300,6 +301,8 @@ TempoMap::TempoMap (framecnt_t fr)
 
 TempoMap::~TempoMap ()
 {
+	delete metrics;
+	delete _map;
 }
 
 void
@@ -308,7 +311,7 @@ TempoMap::remove_tempo (const TempoSection& tempo, bool complete_operation)
 	bool removed = false;
 
 	{
-		Glib::RWLock::WriterLock lm (lock);
+		Glib::RWLock::WriterLock lm (metrics_lock);
 		Metrics::iterator i;
 
 		for (i = metrics->begin(); i != metrics->end(); ++i) {
@@ -322,13 +325,10 @@ TempoMap::remove_tempo (const TempoSection& tempo, bool complete_operation)
 				}
 			}
 		}
-
-		if (removed && complete_operation) {
-			recompute_map (false);
-		}
 	}
 
 	if (removed && complete_operation) {
+		recompute_map (false);
 		PropertyChanged (PropertyChange ());
 	}
 }
@@ -339,7 +339,7 @@ TempoMap::remove_meter (const MeterSection& tempo, bool complete_operation)
 	bool removed = false;
 
 	{
-		Glib::RWLock::WriterLock lm (lock);
+		Glib::RWLock::WriterLock lm (metrics_lock);
 		Metrics::iterator i;
 
 		for (i = metrics->begin(); i != metrics->end(); ++i) {
@@ -353,15 +353,10 @@ TempoMap::remove_meter (const MeterSection& tempo, bool complete_operation)
 				}
 			}
 		}
-		
-		if (removed && complete_operation) {
-			recompute_map (true);
-		}
-
-
 	}
 
 	if (removed && complete_operation) {
+		recompute_map (true);
 		PropertyChanged (PropertyChange ());
 	}
 }
@@ -369,9 +364,6 @@ TempoMap::remove_meter (const MeterSection& tempo, bool complete_operation)
 void
 TempoMap::do_insert (MetricSection* section)
 {
-	/* CALLER MUST HOLD WRITE LOCK */
-
-	bool reassign_tempo_bbt = false;
 	bool need_add = true;
 
 	assert (section->start().ticks == 0);
@@ -386,8 +378,6 @@ TempoMap::do_insert (MetricSection* section)
 		   sections based on this new meter.
 		*/
 		
-		reassign_tempo_bbt = true;
-
 		if ((section->start().beats != 1) || (section->start().ticks != 0)) {
 			
 			BBT_Time corrected = section->start();
@@ -469,8 +459,6 @@ TempoMap::do_insert (MetricSection* section)
 			metrics->insert (metrics->end(), section);
 		}
 	}
-
-	recompute_map (reassign_tempo_bbt);
 }
 
 void
@@ -482,9 +470,12 @@ TempoMap::replace_tempo (const TempoSection& ts, const Tempo& tempo, const BBT_T
 		remove_tempo (ts, false);
 		add_tempo (tempo, where);
 	} else {
-		Glib::RWLock::WriterLock lm (lock);
-		/* cannot move the first tempo section */
-		*((Tempo*)&first) = tempo;
+		{
+			Glib::RWLock::WriterLock lm (metrics_lock);
+			/* cannot move the first tempo section */
+			*((Tempo*)&first) = tempo;
+		}
+
 		recompute_map (false);
 	}
 
@@ -495,7 +486,7 @@ void
 TempoMap::add_tempo (const Tempo& tempo, BBT_Time where)
 {
 	{
-		Glib::RWLock::WriterLock lm (lock);
+		Glib::RWLock::WriterLock lm (metrics_lock);
 
 		/* new tempos always start on a beat */
 		where.ticks = 0;
@@ -531,10 +522,12 @@ TempoMap::add_tempo (const Tempo& tempo, BBT_Time where)
 		ts->update_bar_offset_from_bbt (*meter);
 
 		/* and insert it */
-
+		
 		do_insert (ts);
 	}
 
+	recompute_map (false);
+
 	PropertyChanged (PropertyChange ());
 }
 
@@ -547,9 +540,11 @@ TempoMap::replace_meter (const MeterSection& ms, const Meter& meter, const BBT_T
 		remove_meter (ms, false);
 		add_meter (meter, where);
 	} else {
-		Glib::RWLock::WriterLock lm (lock);
-		/* cannot move the first meter section */
-		*((Meter*)&first) = meter;
+		{
+			Glib::RWLock::WriterLock lm (metrics_lock);
+			/* cannot move the first meter section */
+			*((Meter*)&first) = meter;
+		}
 		recompute_map (true);
 	}
 
@@ -560,7 +555,7 @@ void
 TempoMap::add_meter (const Meter& meter, BBT_Time where)
 {
 	{
-		Glib::RWLock::WriterLock lm (lock);
+		Glib::RWLock::WriterLock lm (metrics_lock);
 
 		/* a new meter always starts a new bar on the first beat. so
 		   round the start time appropriately. remember that
@@ -576,10 +571,12 @@ TempoMap::add_meter (const Meter& meter, BBT_Time where)
 
 		/* new meters *always* start on a beat. */
 		where.ticks = 0;
-
+		
 		do_insert (new MeterSection (where, meter.divisions_per_bar(), meter.note_divisor()));
 	}
 
+	recompute_map (true);
+	
 #ifndef NDEBUG
 	if (DEBUG_ENABLED(DEBUG::TempoMap)) {
 		dump (std::cerr);
@@ -598,10 +595,10 @@ TempoMap::change_initial_tempo (double beats_per_minute, double note_type)
 	for (Metrics::iterator i = metrics->begin(); i != metrics->end(); ++i) {
 		if ((t = dynamic_cast<TempoSection*> (*i)) != 0) {
 			{
-				Glib::RWLock::WriterLock lm (lock);
+				Glib::RWLock::WriterLock lm (metrics_lock);
 				*((Tempo*) t) = newtempo;
-				recompute_map (false);
 			}
+			recompute_map (false);
 			PropertyChanged (PropertyChange ());
 			break;
 		}
@@ -648,12 +645,12 @@ TempoMap::change_existing_tempo_at (framepos_t where, double beats_per_minute, d
 	/* reset */
 
 	{
-		Glib::RWLock::WriterLock lm (lock);
+		Glib::RWLock::WriterLock lm (metrics_lock);
 		/* cannot move the first tempo section */
 		*((Tempo*)prev) = newtempo;
-		recompute_map (false);
 	}
 
+	recompute_map (false);
 	PropertyChanged (PropertyChange ());
 }
 
@@ -774,7 +771,14 @@ TempoMap::timestamp_metrics_from_audio_time ()
 void
 TempoMap::require_map_to (framepos_t pos)
 {
-	if (_map.empty() || _map.back().frame < pos) {
+	bool revise_map;
+
+	{
+		Glib::RWLock::ReaderLock lm (map_lock);
+		revise_map = (_map->empty() || _map->back().frame < pos);
+	}
+
+	if (revise_map) {
 		recompute_map (false, pos);
 	}
 }
@@ -782,7 +786,14 @@ TempoMap::require_map_to (framepos_t pos)
 void
 TempoMap::require_map_to (const BBT_Time& bbt)
 {
-	if (_map.empty() || _map.back().bbt() < bbt) {
+	bool revise_map;
+
+	{
+		Glib::RWLock::ReaderLock lm (map_lock);
+		revise_map = (_map->empty() || _map->back().bbt() < bbt);
+	}
+
+	if (revise_map) {
 		recompute_map (false, 99);
 	}
 }
@@ -799,20 +810,24 @@ TempoMap::recompute_map (bool reassign_tempo_bbt, framepos_t end)
 	double current_frame;
 	BBT_Time current;
 	Metrics::iterator next_metric;
+	BBTPointList* new_map = new BBTPointList;
 
 	if (end < 0) {
-		if (_map.empty()) {
+
+		Glib::RWLock::ReaderLock lm (map_lock);
+
+		if (_map->empty()) {
 			/* compute 1 mins worth */
 			end = _frame_rate * 60;
 		} else {
-			end = _map.back().frame;
+			end = _map->back().frame;
 		}
 	}
 
 	DEBUG_TRACE (DEBUG::TempoMath, string_compose ("recomputing tempo map, zero to %1\n", end));
-	
-	_map.clear ();
 
+	Glib::RWLock::ReaderLock lm (metrics_lock);
+	
 	for (Metrics::iterator i = metrics->begin(); i != metrics->end(); ++i) {
 		if ((ms = dynamic_cast<MeterSection *> (*i)) != 0) {
 			meter = ms;
@@ -873,7 +888,7 @@ TempoMap::recompute_map (bool reassign_tempo_bbt, framepos_t end)
 	++next_metric; // skip tempo (or meter)
 
 	DEBUG_TRACE (DEBUG::TempoMath, string_compose ("Add first bar at 1|1 @ %2\n", current.bars, current_frame));
-	_map.push_back (BBTPoint (*meter, *tempo,(framepos_t) llrint(current_frame), 1, 1));
+	new_map->push_back (BBTPoint (*meter, *tempo,(framepos_t) llrint(current_frame), 1, 1));
 
 	while (current_frame < end) {
 		
@@ -973,18 +988,24 @@ TempoMap::recompute_map (bool reassign_tempo_bbt, framepos_t end)
 
 		if (current.beats == 1) {
 			DEBUG_TRACE (DEBUG::TempoMath, string_compose ("Add Bar at %1|1 @ %2\n", current.bars, current_frame));
-			_map.push_back (BBTPoint (*meter, *tempo,(framepos_t) llrint(current_frame), current.bars, 1));
+			new_map->push_back (BBTPoint (*meter, *tempo,(framepos_t) llrint(current_frame), current.bars, 1));
 		} else {
 			DEBUG_TRACE (DEBUG::TempoMath, string_compose ("Add Beat at %1|%2 @ %3\n", current.bars, current.beats, current_frame));
-			_map.push_back (BBTPoint (*meter, *tempo, (framepos_t) llrint(current_frame), current.bars, current.beats));
+			new_map->push_back (BBTPoint (*meter, *tempo, (framepos_t) llrint(current_frame), current.bars, current.beats));
 		}
 	}
+
+	{
+		Glib::RWLock::WriterLock lm (map_lock);
+		swap (_map, new_map);
+		delete new_map;
+	}
 }
 
 TempoMetric
 TempoMap::metric_at (framepos_t frame) const
 {
-	Glib::RWLock::ReaderLock lm (lock);
+	Glib::RWLock::ReaderLock lm (metrics_lock);
 	TempoMetric m (first_meter(), first_tempo());
 	const Meter* meter;
 	const Tempo* tempo;
@@ -1021,7 +1042,7 @@ TempoMap::metric_at (framepos_t frame) const
 TempoMetric
 TempoMap::metric_at (BBT_Time bbt) const
 {
-	Glib::RWLock::ReaderLock lm (lock);
+	Glib::RWLock::ReaderLock lm (metrics_lock);
 	TempoMetric m (first_meter(), first_tempo());
 	const Meter* meter;
 	const Tempo* tempo;
@@ -1058,7 +1079,7 @@ void
 TempoMap::bbt_time (framepos_t frame, BBT_Time& bbt)
 {
 	{
-		Glib::RWLock::ReaderLock lm (lock);
+		Glib::RWLock::ReaderLock lm (map_lock);
 		BBTPointList::const_iterator i = bbt_before_or_at (frame);
 		bbt_time_unlocked (frame, bbt, i);
 	}
@@ -1081,7 +1102,7 @@ TempoMap::bbt_time_unlocked (framepos_t frame, BBT_Time& bbt, const BBTPointList
 framepos_t
 TempoMap::frame_time (const BBT_Time& bbt)
 {
-	Glib::RWLock::ReaderLock lm (lock);
+	Glib::RWLock::ReaderLock lm (map_lock);
 
 	BBTPointList::const_iterator s = bbt_point_for (BBT_Time (1, 1, 0));
 	BBTPointList::const_iterator e = bbt_point_for (BBT_Time (bbt.bars, bbt.beats, 0));
@@ -1097,7 +1118,7 @@ TempoMap::frame_time (const BBT_Time& bbt)
 framecnt_t
 TempoMap::bbt_duration_at (framepos_t pos, const BBT_Time& bbt, int dir)
 {
-	Glib::RWLock::ReaderLock lm (lock);
+	Glib::RWLock::ReaderLock lm (map_lock);
 	framecnt_t frames = 0;
 	BBT_Time when;
 
@@ -1119,7 +1140,7 @@ TempoMap::bbt_duration_at_unlocked (const BBT_Time& when, const BBT_Time& bbt, i
 	BBTPointList::const_iterator start (wi);
 	double tick_frames = 0;
 
-	assert (wi != _map.end());
+	assert (wi != _map->end());
 
 	/* compute how much rounding we did because of non-zero ticks */
 
@@ -1130,19 +1151,19 @@ TempoMap::bbt_duration_at_unlocked (const BBT_Time& when, const BBT_Time& bbt, i
 	uint32_t bars = 0;
 	uint32_t beats = 0;
 
-	while (wi != _map.end() && bars < bbt.bars) {
+	while (wi != _map->end() && bars < bbt.bars) {
 		++wi;
 		if ((*wi).is_bar()) {
 			++bars;
 		}
 	}
-	assert (wi != _map.end());
+	assert (wi != _map->end());
 
-	while (wi != _map.end() && beats < bbt.beats) {
+	while (wi != _map->end() && beats < bbt.beats) {
 		++wi;
 		++beats;
 	}
-	assert (wi != _map.end());
+	assert (wi != _map->end());
 
 	/* add any additional frames related to ticks in the added value */
 
@@ -1156,25 +1177,19 @@ TempoMap::bbt_duration_at_unlocked (const BBT_Time& when, const BBT_Time& bbt, i
 framepos_t
 TempoMap::round_to_bar (framepos_t fr, int dir)
 {
-	{
-		Glib::RWLock::ReaderLock lm (lock);
-		return round_to_type (fr, dir, Bar);
-	}
+	return round_to_type (fr, dir, Bar);
 }
 
 framepos_t
 TempoMap::round_to_beat (framepos_t fr, int dir)
 {
-	{
-		Glib::RWLock::ReaderLock lm (lock);
-		return round_to_type (fr, dir, Beat);
-	}
+	return round_to_type (fr, dir, Beat);
 }
 
 framepos_t
 TempoMap::round_to_beat_subdivision (framepos_t fr, int sub_num, int dir)
 {
-	Glib::RWLock::ReaderLock lm (lock);
+	Glib::RWLock::ReaderLock lm (map_lock);
 	BBTPointList::const_iterator i = bbt_before_or_at (fr);
 	BBT_Time the_beat;
 	uint32_t ticks_one_subdivisions_worth;
@@ -1204,9 +1219,9 @@ TempoMap::round_to_beat_subdivision (framepos_t fr, int sub_num, int dir)
 		}
 
 		if (the_beat.ticks > BBT_Time::ticks_per_bar_division) {
-			assert (i != _map.end());
+			assert (i != _map->end());
 			++i;
-			assert (i != _map.end());
+			assert (i != _map->end());
 			the_beat.ticks -= BBT_Time::ticks_per_bar_division;
 		} 
 
@@ -1229,7 +1244,7 @@ TempoMap::round_to_beat_subdivision (framepos_t fr, int sub_num, int dir)
 		}
 
 		if (the_beat.ticks < difference) {
-			if (i == _map.begin()) {
+			if (i == _map->begin()) {
 				/* can't go backwards from wherever pos is, so just return it */
 				return fr;
 			}
@@ -1255,9 +1270,9 @@ TempoMap::round_to_beat_subdivision (framepos_t fr, int sub_num, int dir)
 			DEBUG_TRACE (DEBUG::SnapBBT, string_compose ("moved forward to %1\n", the_beat.ticks));
 
 			if (the_beat.ticks > BBT_Time::ticks_per_bar_division) {
-				assert (i != _map.end());
+				assert (i != _map->end());
 				++i;
-				assert (i != _map.end());
+				assert (i != _map->end());
 				the_beat.ticks -= BBT_Time::ticks_per_bar_division;
 				DEBUG_TRACE (DEBUG::SnapBBT, string_compose ("fold beat to %1\n", the_beat));
 			} 
@@ -1267,7 +1282,7 @@ TempoMap::round_to_beat_subdivision (framepos_t fr, int sub_num, int dir)
 			/* closer to previous subdivision, so shift backward */
 
 			if (rem > the_beat.ticks) {
-				if (i == _map.begin()) {
+				if (i == _map->begin()) {
 					/* can't go backwards past zero, so ... */
 					return 0;
 				}
@@ -1291,6 +1306,7 @@ TempoMap::round_to_beat_subdivision (framepos_t fr, int sub_num, int dir)
 framepos_t
 TempoMap::round_to_type (framepos_t frame, int dir, BBTPointType type)
 {
+	Glib::RWLock::ReaderLock lm (map_lock);
 	BBTPointList::const_iterator fi;
 
 	if (dir > 0) {
@@ -1299,7 +1315,7 @@ TempoMap::round_to_type (framepos_t frame, int dir, BBTPointType type)
 		fi = bbt_before_or_at (frame);
 	}
 
-	assert (fi != _map.end());
+	assert (fi != _map->end());
 
 	DEBUG_TRACE(DEBUG::SnapBBT, string_compose ("round from %1 (%3|%4 @ %5) to bars in direction %2\n", frame, dir, (*fi).bar, (*fi).beat, (*fi).frame));
 		
@@ -1313,7 +1329,7 @@ TempoMap::round_to_type (framepos_t frame, int dir, BBTPointType type)
 			}
 
 			while (!(*fi).is_bar()) {
-				if (fi == _map.begin()) {
+				if (fi == _map->begin()) {
 					break;
 				}
 				fi--;
@@ -1332,7 +1348,7 @@ TempoMap::round_to_type (framepos_t frame, int dir, BBTPointType type)
 
 			while (!(*fi).is_bar()) {
 				fi++;
-				if (fi == _map.end()) {
+				if (fi == _map->end()) {
 					--fi;
 					break;
 				}
@@ -1354,7 +1370,7 @@ TempoMap::round_to_type (framepos_t frame, int dir, BBTPointType type)
 			}
 
 			while ((*prev).beat != 1) {
-				if (prev == _map.begin()) {
+				if (prev == _map->begin()) {
 					break;
 				}
 				prev--;
@@ -1362,7 +1378,7 @@ TempoMap::round_to_type (framepos_t frame, int dir, BBTPointType type)
 
 			while ((*next).beat != 1) {
 				next++;
-				if (next == _map.end()) {
+				if (next == _map->end()) {
 					--next;
 					break;
 				}
@@ -1425,18 +1441,15 @@ TempoMap::map (TempoMap::BBTPointList::const_iterator& begin,
 	       TempoMap::BBTPointList::const_iterator& end, 
 	       framepos_t lower, framepos_t upper) 
 {
-	if (_map.empty() || upper >= _map.back().frame) {
-		recompute_map (false, upper);
-	}
-
-	begin = lower_bound (_map.begin(), _map.end(), lower);
-	end = upper_bound (_map.begin(), _map.end(), upper);
+	require_map_to (upper);
+	begin = lower_bound (_map->begin(), _map->end(), lower);
+	end = upper_bound (_map->begin(), _map->end(), upper);
 }
 
 const TempoSection&
 TempoMap::tempo_section_at (framepos_t frame) const
 {
-	Glib::RWLock::ReaderLock lm (lock);
+	Glib::RWLock::ReaderLock lm (metrics_lock);
 	Metrics::const_iterator i;
 	TempoSection* prev = 0;
 
@@ -1482,7 +1495,7 @@ TempoMap::get_state ()
 	XMLNode *root = new XMLNode ("TempoMap");
 
 	{
-		Glib::RWLock::ReaderLock lm (lock);
+		Glib::RWLock::ReaderLock lm (metrics_lock);
 		for (i = metrics->begin(); i != metrics->end(); ++i) {
 			root->add_child_nocopy ((*i)->get_state());
 		}
@@ -1495,7 +1508,7 @@ int
 TempoMap::set_state (const XMLNode& node, int /*version*/)
 {
 	{
-		Glib::RWLock::WriterLock lm (lock);
+		Glib::RWLock::WriterLock lm (metrics_lock);
 
 		XMLNodeList nlist;
 		XMLNodeConstIterator niter;
@@ -1545,13 +1558,12 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
 		}
 
 		if (niter == nlist.end()) {
-
 			MetricSectionSorter cmp;
 			metrics->sort (cmp);
-			recompute_map (true);
 		}
 	}
 
+	recompute_map (true);
 	PropertyChanged (PropertyChange ());
 
 	return 0;
@@ -1560,6 +1572,7 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
 void
 TempoMap::dump (std::ostream& o) const
 {
+	Glib::RWLock::ReaderLock lm (metrics_lock);
 	const MeterSection* m;
 	const TempoSection* t;
 
@@ -1578,7 +1591,7 @@ TempoMap::dump (std::ostream& o) const
 int
 TempoMap::n_tempos() const
 {
-	Glib::RWLock::ReaderLock lm (lock);
+	Glib::RWLock::ReaderLock lm (metrics_lock);
 	int cnt = 0;
 
 	for (Metrics::const_iterator i = metrics->begin(); i != metrics->end(); ++i) {
@@ -1593,7 +1606,7 @@ TempoMap::n_tempos() const
 int
 TempoMap::n_meters() const
 {
-	Glib::RWLock::ReaderLock lm (lock);
+	Glib::RWLock::ReaderLock lm (metrics_lock);
 	int cnt = 0;
 
 	for (Metrics::const_iterator i = metrics->begin(); i != metrics->end(); ++i) {
@@ -1608,6 +1621,7 @@ TempoMap::n_meters() const
 void
 TempoMap::insert_time (framepos_t where, framecnt_t amount)
 {
+	Glib::RWLock::WriterLock lm (metrics_lock);
 	for (Metrics::iterator i = metrics->begin(); i != metrics->end(); ++i) {
 		if ((*i)->frame() >= where && (*i)->movable ()) {
 			(*i)->set_frame ((*i)->frame() + amount);
@@ -1638,6 +1652,7 @@ TempoMap::framepos_minus_beats (framepos_t pos, Evoral::MusicalTime beats)
 framepos_t
 TempoMap::framepos_minus_bbt (framepos_t pos, BBT_Time op)
 {
+	Glib::RWLock::ReaderLock lm (map_lock);
 	BBTPointList::const_iterator i;
 	framecnt_t extra_frames = 0;
 
@@ -1650,7 +1665,7 @@ TempoMap::framepos_minus_bbt (framepos_t pos, BBT_Time op)
 	
 	/* walk backwards */
 
-	while (i != _map.begin() && (op.bars || op.beats)) {
+	while (i != _map->begin() && (op.bars || op.beats)) {
 		--i;
 		if ((*i).is_bar()) {
 			if (op.bars) {
@@ -1683,6 +1698,7 @@ TempoMap::framepos_minus_bbt (framepos_t pos, BBT_Time op)
 framepos_t
 TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op)
 {
+	Glib::RWLock::ReaderLock lm (map_lock);
 	BBT_Time op_copy (op);
 	int additional_minutes = 1;
 	BBTPointList::const_iterator i;
@@ -1697,7 +1713,7 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op)
 		/* we know that (*i).frame is before or equal to pos */
 		backup_frames = pos - (*i).frame;
 
-		while (i != _map.end() && (op.bars || op.beats)) {
+		while (i != _map->end() && (op.bars || op.beats)) {
 			++i;
 			if ((*i).is_bar()) {
 				if (op.bars) {
@@ -1710,7 +1726,7 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op)
 			}
 		}
 		
-		if (i != _map.end()) {
+		if (i != _map->end()) {
 			break;
 		}
 
@@ -1722,7 +1738,7 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op)
 
 		/* go back and try again */
 		warning << "reached end of map with op now at " << op << " end = " 
-			<< _map.back().frame << ' ' << _map.back().bar << '|' << _map.back().beat << ", trying to walk " 
+			<< _map->back().frame << ' ' << _map->back().bar << '|' << _map->back().beat << ", trying to walk " 
 			<< op_copy << " ... retry" 
 			<< endmsg;
 	}
@@ -1741,6 +1757,7 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op)
 Evoral::MusicalTime
 TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance)
 {
+	Glib::RWLock::ReaderLock lm (map_lock);
 	BBTPointList::const_iterator i = bbt_after_or_at (pos);
 	Evoral::MusicalTime beats = 0;
 	framepos_t end = pos + distance;
@@ -1755,11 +1772,11 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance)
 		beats += ((*i).frame - pos) / (*i).meter->frames_per_division (*(*i).tempo, _frame_rate);
 	}
 
-	while (i != _map.end() && (*i).frame < end) {
+	while (i != _map->end() && (*i).frame < end) {
 		++i;
 		beats++;
 	}
-	assert (i != _map.end());
+	assert (i != _map->end());
 	
 	/* if our ending BBTPoint is after the end, subtract a fractional beat
 	   to represent that distance.
@@ -1775,12 +1792,17 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance)
 TempoMap::BBTPointList::const_iterator
 TempoMap::bbt_before_or_at (framepos_t pos)
 {
+	BBTPointList::const_iterator i;
+
 	require_map_to (pos);
-	BBTPointList::const_iterator i = lower_bound (_map.begin(), _map.end(), pos);
-	assert (i != _map.end());
-	if ((*i).frame > pos) {
-		assert (i != _map.begin());
-		--i;
+	{
+		Glib::RWLock::ReaderLock lm (map_lock);
+		i = lower_bound (_map->begin(), _map->end(), pos);
+		assert (i != _map->end());
+		if ((*i).frame > pos) {
+			assert (i != _map->begin());
+			--i;
+		}
 	}
 	return i;
 }
@@ -1788,9 +1810,14 @@ TempoMap::bbt_before_or_at (framepos_t pos)
 TempoMap::BBTPointList::const_iterator
 TempoMap::bbt_after_or_at (framepos_t pos)
 {
+	BBTPointList::const_iterator i;
+
 	require_map_to (pos);
-	BBTPointList::const_iterator i = upper_bound (_map.begin(), _map.end(), pos);
-	assert (i != _map.end());
+	{
+		Glib::RWLock::ReaderLock lm (map_lock);
+		i = upper_bound (_map->begin(), _map->end(), pos);
+		assert (i != _map->end());
+	}
 	return i;
 }
 
@@ -1803,17 +1830,28 @@ struct bbtcmp {
 TempoMap::BBTPointList::const_iterator
 TempoMap::bbt_point_for (const BBT_Time& bbt)
 {
+	BBTPointList::const_iterator i;
 	bbtcmp cmp;
 	int additional_minutes = 1;
 
-	while (_map.empty() || _map.back().bar < (bbt.bars + 1)) {
+	while (1) {
+		{
+			Glib::RWLock::ReaderLock lm (map_lock);
+			if (!_map->empty() && _map->back().bar >= (bbt.bars + 1)) {
+				break;
+			}
+		}
 		/* add some more distance, using bigger steps each time */
-		require_map_to (_map.back().frame + (_frame_rate * 60 * additional_minutes));
+		require_map_to (_map->back().frame + (_frame_rate * 60 * additional_minutes));
 		additional_minutes *= 2;
 	}
 
-	BBTPointList::const_iterator i = lower_bound (_map.begin(), _map.end(), bbt, cmp);
-	assert (i != _map.end());
+	{
+		Glib::RWLock::ReaderLock lm (map_lock);
+		i = lower_bound (_map->begin(), _map->end(), bbt, cmp);
+		assert (i != _map->end());
+	}
+
 	return i;
 }