From 9875a958295353aabba73fb05f862c4f92ebb219 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Sat, 18 Apr 2020 23:54:24 +0200
Subject: RAII collect processor-change signals

---
 libs/ardour/ardour/session.h     | 29 +++++++++++++++++------------
 libs/ardour/session.cc           |  1 +
 libs/ardour/session_process.cc   | 18 +++++++++++-------
 libs/ardour/session_transport.cc |  1 +
 4 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 4c93ecb95f..4c259232f5 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -646,23 +646,27 @@ public:
 	};
 
 	class ProcessorChangeBlocker {
-		public:
-			ProcessorChangeBlocker (Session* s, bool rc = true)
-				: _session (s)
-				, _reconfigure_on_delete (rc)
-			{
-				g_atomic_int_inc (&s->_ignore_route_processor_changes);
-			}
-			~ProcessorChangeBlocker () {
-				if (g_atomic_int_dec_and_test (&_session->_ignore_route_processor_changes)) {
+	public:
+		ProcessorChangeBlocker (Session* s, bool rc = true)
+			: _session (s)
+			, _reconfigure_on_delete (rc)
+		{
+			g_atomic_int_inc (&s->_ignore_route_processor_changes);
+		}
+
+		~ProcessorChangeBlocker ()
+		{
+			if (g_atomic_int_dec_and_test (&_session->_ignore_route_processor_changes)) {
+				if (g_atomic_int_compare_and_exchange (&_session->_ignored_a_processor_change, 1, 0)) {
 					if (_reconfigure_on_delete) {
 						_session->route_processors_changed (RouteProcessorChange ());
 					}
 				}
 			}
-		private:
-			Session* _session;
-			bool _reconfigure_on_delete;
+		}
+	private:
+		Session* _session;
+		bool _reconfigure_on_delete;
 	};
 
 	RouteGroup* new_route_group (const std::string&);
@@ -2128,6 +2132,7 @@ private:
 
 	friend class    ProcessorChangeBlocker;
 	gint            _ignore_route_processor_changes; /* atomic */
+	gint            _ignored_a_processor_change;
 
 	MidiClockTicker* midi_clock;
 
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 0c73acdaa5..253a80a4b3 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -314,6 +314,7 @@ Session::Session (AudioEngine &eng,
 	, _suspend_timecode_transmission (0)
 	,  _speakers (new Speakers)
 	, _ignore_route_processor_changes (0)
+	, _ignored_a_processor_change (0)
 	, midi_clock (0)
 	, _scene_changer (0)
 	, _midi_ports (0)
diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index f5613d3af4..828299d8e0 100644
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -102,14 +102,17 @@ Session::process (pframes_t nframes)
 	 * Route::process_output_buffers() but various functions
 	 * callig it hold a _processor_lock reader-lock
 	 */
-	boost::shared_ptr<RouteList> r = routes.reader ();
 	bool one_or_more_routes_declicking = false;
-	for (RouteList::const_iterator i = r->begin(); i != r->end(); ++i) {
-		if ((*i)->apply_processor_changes_rt()) {
-			_rt_emit_pending = true;
-		}
-		if ((*i)->declick_in_progress()) {
-			one_or_more_routes_declicking = true;
+	{
+		ProcessorChangeBlocker pcb (this);
+		boost::shared_ptr<RouteList> r = routes.reader ();
+		for (RouteList::const_iterator i = r->begin(); i != r->end(); ++i) {
+			if ((*i)->apply_processor_changes_rt()) {
+				_rt_emit_pending = true;
+			}
+			if ((*i)->declick_in_progress()) {
+				one_or_more_routes_declicking = true;
+			}
 		}
 	}
 
@@ -1051,6 +1054,7 @@ Session::emit_route_signals ()
 {
 	// TODO use RAII to allow using these signals in other places
 	BatchUpdateStart(); /* EMIT SIGNAL */
+	ProcessorChangeBlocker pcb (this);
 	boost::shared_ptr<RouteList> r = routes.reader ();
 	for (RouteList::const_iterator ci = r->begin(); ci != r->end(); ++ci) {
 		(*ci)->emit_pending_signals ();
diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index f136eebc5d..2924629d88 100644
--- a/libs/ardour/session_transport.cc
+++ b/libs/ardour/session_transport.cc
@@ -1851,6 +1851,7 @@ void
 Session::route_processors_changed (RouteProcessorChange c)
 {
 	if (g_atomic_int_get (&_ignore_route_processor_changes) > 0) {
+		g_atomic_int_set (&_ignored_a_processor_change, 1);
 		return;
 	}
 
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