From dcc0f1cb17724b41b45f9dee5c1a29ceb6af5872 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Wed, 12 May 2021 19:22:35 +0200
Subject: [PATCH] Fix playlist edit after edit race

After an edit option the playlist is thawed and triggers
the butler thread (SessionEvent::Overwrite) to re-read the
playlist.

If another edit operation is started the butler may reads a
region using the region's new position, but the playlist's
old range.

See also 4db1c02bd1a0e4da9efd725cd8fb098ba7c4abe5
---
 libs/ardour/playlist.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libs/ardour/playlist.cc b/libs/ardour/playlist.cc
index 98a70d0518..8b536a30d5 100644
--- a/libs/ardour/playlist.cc
+++ b/libs/ardour/playlist.cc
@@ -449,6 +449,10 @@ Playlist::end_undo ()
 void
 Playlist::freeze ()
 {
+	/* flush any ongoing reads, paricularly AudioPlaylist::read(),
+	 * before beginning to modify the playlist.
+	 */
+	RegionWriteLock rlock (this);
 	delay_notifications ();
 	g_atomic_int_inc (&ignore_state_changes);
 }