Towards fixing no_roll()

Currently ::roll() may actually be a ::no_roll() under some circumstances.

This can also happen during count-in:
  transport_stopped () == transport_rolling()

and during latency-preroll:
   Global session-transport speed != 0, some tracks already roll,
   read data from disk and feed latent plugins.
   but other non-latent tracks or busses don't roll and still have to
   behave like the switch from no_roll() to roll() has not yet happened.

This changes the game WRT to monitoring as well, previously, Route:roll()
called Route::no_roll_unlocked () for conditions outlined above.
Now Track::no_roll_unlocked is called and in some cases wrongly clears
the buffers before the signal hits the disk-writer. (more work is needed
related to 61f8e53b)

On the upside this also fixes an issue with MidiTrack::no_roll not keeping
a lock while pushing data into the step-edit-ringbuffer.

This is also a step towards consolidating all entry points:
::roll(), ::no_roll(), ::silent_roll() in the Route class.

6 files changed, 20 insertions, 30 deletions

diff --git a/libs/ardour/ardour/midi_track.h b/libs/ardour/ardour/midi_track.h
index 8ed4dfc7b1..dfd5a42d13 100644
--- a/libs/ardour/ardour/midi_track.h
+++ b/libs/ardour/ardour/midi_track.h
@@ -150,7 +150,7 @@ private:
 	void set_state_part_two ();
 	void set_state_part_three ();
 
-	int no_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool state_changing);
+	int no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool state_changing);
 	void push_midi_input_to_step_edit_ringbuffer (samplecnt_t nframes);
 
 	void track_input_active (IOChange, void*);
diff --git a/libs/ardour/ardour/route.h b/libs/ardour/ardour/route.h
index c0f2048a18..5376635076 100644
--- a/libs/ardour/ardour/route.h
+++ b/libs/ardour/ardour/route.h
@@ -138,14 +138,11 @@ public:
 
 	virtual void filter_input (BufferSet &) {}
 
-	virtual int roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample,
-	                  int declick, bool& need_butler);
+	int roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, int declick, bool& need_butler);
 
-	virtual int no_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample,
-	                     bool state_changing);
+	int no_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool state_changing);
 
-	virtual int silent_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample,
-	                         bool& need_butler);
+	int silent_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool& need_butler);
 
 	virtual bool can_record() { return false; }
 
@@ -589,8 +586,8 @@ public:
 
 	virtual void use_captured_sources (SourceList& srcs, CaptureInfos const &) {}
 
-  protected:
-        friend class Session;
+protected:
+	friend class Session;
 
 	void catch_up_on_solo_mute_override ();
 	void set_listen (bool);
@@ -598,6 +595,8 @@ public:
 	void curve_reallocate ();
 	virtual void set_block_size (pframes_t nframes);
 
+	virtual int no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool session_state_changing);
+
 	void fill_buffers_with_input (BufferSet& bufs, boost::shared_ptr<IO> io, pframes_t nframes);
 
 	void passthru (BufferSet&, samplepos_t start_sample, samplepos_t end_sample, pframes_t nframes, int declick, bool gain_automation_ok, bool run_disk_reader);
@@ -747,7 +746,6 @@ private:
 
 	void setup_invisible_processors ();
 
-	void no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample);
 	pframes_t latency_preroll (pframes_t nframes, samplepos_t& start_sample, samplepos_t& end_sample);
 
 	void reset_instrument_info ();
diff --git a/libs/ardour/ardour/track.h b/libs/ardour/ardour/track.h
index df40ac092f..c468f26035 100644
--- a/libs/ardour/ardour/track.h
+++ b/libs/ardour/ardour/track.h
@@ -65,8 +65,7 @@ class LIBARDOUR_API Track : public Route, public Recordable
 
 	bool set_processor_state (XMLNode const & node, XMLProperty const* prop, ProcessorList& new_order, bool& must_configure);
 
-	virtual int no_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample,
-	                     bool state_changing);
+	virtual int no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool state_changing);
 
 	bool needs_butler() const { return _needs_butler; }
 
diff --git a/libs/ardour/midi_track.cc b/libs/ardour/midi_track.cc
index dc5f3f0a80..2e5fd2a0b4 100644
--- a/libs/ardour/midi_track.cc
+++ b/libs/ardour/midi_track.cc
@@ -318,9 +318,9 @@ MidiTrack::update_controls(const BufferSet& bufs)
 }
 
 int
-MidiTrack::no_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool state_changing)
+MidiTrack::no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool state_changing)
 {
-	int ret = Track::no_roll (nframes, start_sample, end_sample, state_changing);
+	int ret = Track::no_roll_unlocked (nframes, start_sample, end_sample, state_changing);
 
 	if (ret == 0 && _step_editing) {
 		push_midi_input_to_step_edit_ringbuffer (nframes);
diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index f411631e9e..389809190a 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -3656,6 +3656,12 @@ Route::no_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sam
 		return 0;
 	}
 
+	return no_roll_unlocked (nframes, start_sample, end_sample, session_state_changing);
+}
+
+int
+Route::no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool session_state_changing)
+{
 	if (!_active) {
 		silence_unlocked (nframes);
 		return 0;
@@ -3676,14 +3682,6 @@ Route::no_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sam
 		*/
 	}
 
-	no_roll_unlocked (nframes, start_sample, end_sample);
-
-	return 0;
-}
-
-void
-Route::no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample)
-{
 	BufferSet& bufs = _session.get_route_buffers (n_process_buffers());
 
 	fill_buffers_with_input (bufs, _input, nframes);
@@ -3698,6 +3696,7 @@ Route::no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_
 	passthru (bufs, start_sample, end_sample, nframes, 0, true, false);
 
 	flush_processor_buffers_locked (nframes);
+	return 0;
 }
 
 samplecnt_t
@@ -3731,7 +3730,7 @@ Route::latency_preroll (pframes_t nframes, samplepos_t& start_sample, samplepos_
 	}
 
 	if (latency_preroll > playback_latency ()) {
-		no_roll_unlocked (nframes, start_sample - latency_preroll, end_sample - latency_preroll);
+		no_roll_unlocked (nframes, start_sample - latency_preroll, end_sample - latency_preroll, false);
 		return 0;
 	}
 
diff --git a/libs/ardour/track.cc b/libs/ardour/track.cc
index f201abcb12..5aad8b9bcf 100644
--- a/libs/ardour/track.cc
+++ b/libs/ardour/track.cc
@@ -430,14 +430,8 @@ Track::set_name (const string& str)
 }
 
 int
-Track::no_roll (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool session_state_changing)
+Track::no_roll_unlocked (pframes_t nframes, samplepos_t start_sample, samplepos_t end_sample, bool session_state_changing)
 {
-	Glib::Threads::RWLock::ReaderLock lm (_processor_lock, Glib::Threads::TRY_LOCK);
-
-	if (!lm.locked()) {
-		return 0;
-	}
-
 	/* no outputs? nothing to do ... what happens if we have sends etc. ? */
 
 	if (n_outputs().n_total() == 0 && !ARDOUR::Profile->get_mixbus()) {