From c368c26519d05815e9bfadbd02f9de5f5d84321c Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Tue, 29 Oct 2019 16:15:38 -0600
Subject: fix handling of deferred events in transportFSM

tfsm events live on intrusive lists, with only 1 hook, which means they
can only be on one list at a time, and cannot be deleted while part of
the list. This wasn't being addressed properly when deferring (and
undeferring) events.
---
 libs/ardour/ardour/transport_fsm.h |  2 +-
 libs/ardour/transport_fsm.cc       | 48 +++++++++++++++++++++++++++++++-------
 2 files changed, 40 insertions(+), 10 deletions(-)

(limited to 'libs/ardour')

diff --git a/libs/ardour/ardour/transport_fsm.h b/libs/ardour/ardour/transport_fsm.h
index 922f910a12..869611a8ab 100644
--- a/libs/ardour/ardour/transport_fsm.h
+++ b/libs/ardour/ardour/transport_fsm.h
@@ -159,7 +159,7 @@ struct TransportFSM
 	void transition (ButlerState bs);
 
 	void process_events ();
-	bool process_event (Event&);
+	bool process_event (Event&, bool was_deferred, bool& deferred);
 
 	Event _last_locate;
 	Event _last_stop;
diff --git a/libs/ardour/transport_fsm.cc b/libs/ardour/transport_fsm.cc
index 2fd61a3d00..c8b5c65035 100644
--- a/libs/ardour/transport_fsm.cc
+++ b/libs/ardour/transport_fsm.cc
@@ -80,7 +80,19 @@ TransportFSM::process_events ()
 		MotionState oms = _motion_state;
 		ButlerState obs = _butler_state;
 
-		if (process_event (queued_events.front())) { /* event processed successfully */
+		Event* ev = &queued_events.front();
+		bool deferred;
+
+		/* must remove from the queued_events list now, because
+		 * process_event() may defer the event. This will lead to
+		 * insertion into the deferred_events list, and its not possible
+		 * with intrusive lists to be present in two lists at once
+		 * (without additional hooks).
+		 */
+
+		queued_events.pop_front ();
+
+		if (process_event (*ev, false, deferred)) { /* event processed successfully */
 
 			if (oms != _motion_state || obs != _butler_state) {
 
@@ -93,7 +105,8 @@ TransportFSM::process_events ()
 
 					for (EventList::iterator e = deferred_events.begin(); e != deferred_events.end(); ) {
 						Event* deferred_ev = &(*e);
-						if (process_event (*e)) { /* event processed, remove from deferred */
+						bool deferred2;
+						if (process_event (*e, true, deferred2)) { /* event processed, remove from deferred */
 							e = deferred_events.erase (e);
 							delete deferred_ev;
 						} else {
@@ -104,9 +117,9 @@ TransportFSM::process_events ()
 			}
 		}
 
-		Event* ev = &queued_events.front();
-		queued_events.pop_front ();
-		delete ev;
+		if (!deferred) {
+			delete ev;
+		}
 	}
 
 	processing--;
@@ -178,10 +191,12 @@ TransportFSM::bad_transition (Event const & ev)
 }
 
 bool
-TransportFSM::process_event (Event& ev)
+TransportFSM::process_event (Event& ev, bool already_deferred, bool& deferred)
 {
 	DEBUG_TRACE (DEBUG::TFSMEvents, string_compose ("process %1\n", enum_2_string (ev.type)));
 
+	deferred = false;
+
 	switch (ev.type) {
 
 	case StartTransport:
@@ -194,10 +209,16 @@ TransportFSM::process_event (Event& ev)
 			break;
 		case DeclickToLocate:
 		case WaitingForLocate:
-			defer (ev);
+			if (!already_deferred) {
+				defer (ev);
+				deferred = true;
+			}
 			break;
 		case DeclickToStop:
-			defer (ev);
+			if (!already_deferred) {
+				defer (ev);
+				deferred = true;
+			}
 			break;
 		default:
 			bad_transition (ev); return false;
@@ -215,7 +236,10 @@ TransportFSM::process_event (Event& ev)
 			break;
 		case DeclickToLocate:
 		case WaitingForLocate:
-			defer (ev);
+			if (!already_deferred) {
+				defer (ev);
+				deferred = true;
+			}
 			break;
 		default:
 			bad_transition (ev); return false;
@@ -224,6 +248,12 @@ TransportFSM::process_event (Event& ev)
 		break;
 
 	case Locate:
+		DEBUG_TRACE (DEBUG::TFSMEvents, string_compose ("locate, with roll = %1 flush = %2 target = %3 loop %4 force %5\n",
+		                                                ev.with_roll,
+		                                                ev.with_flush,
+		                                                ev.target,
+		                                                ev.with_loop,
+		                                                ev.force));
 		switch (_motion_state) {
 		case Stopped:
 			transition (WaitingForLocate);
-- 
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