From 3ced8cc6bcae213f8e063c6222ae9e9f3512f90a Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 27 Aug 2024 01:09:06 +0200
Subject: [PATCH] RegionFX: fix undo/redo of region state

Previously this caused deadlocks (read lock while holding
write lock), and also not dropped references of plugins.

Ideally undo/redo of FX unrelated region state
will not re-instantiate plugins; we can optimize this later.
---
 libs/ardour/region.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index 9c65b38c18..a90f0bc8cc 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -1579,6 +1579,10 @@ Region::_set_state (const XMLNode& node, int version, PropertyChange& what_chang
 		Glib::Threads::RWLock::WriterLock lm (_fx_lock);
 		bool changed = !_plugins.empty ();
 
+		for (auto const& rfx : _plugins) {
+			rfx->drop_references ();
+		}
+
 		_plugins.clear ();
 
 		for (auto const& child : node.children ()) {
@@ -1596,6 +1600,7 @@ Region::_set_state (const XMLNode& node, int version, PropertyChange& what_chang
 				changed = true;
 			}
 		}
+		lm.release ();
 		if (changed) {
 			fx_latency_changed (true);
 			fx_tail_changed (true);