From 0b6e68869f34da09e296889b0e1a70c5fbacee55 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Sat, 18 May 2024 16:25:04 +0200
Subject: [PATCH] T: fix deadlock when adding tracks

For livetrax, ::add_routes_inner calls ::reassign_track_numbers,
which in turn calls ::livetrax_queue_auto_connect.

This can result in a deadlock:

 * GUI thread, ::add_routes_inner holds the process-lock
   and ::livetrax_queue_auto_connect requests the `_auto_connect_queue_lock`

 * auto-connect thread first takes the `_auto_connect_queue_lock and then
   requests the process-lock
---
 libs/ardour/session.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 604e704cd1..6bfe155edc 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -3681,6 +3681,8 @@ Session::add_routes_inner (RouteList& new_routes, bool input_auto_connect, bool
 					r->enable_direct_outs ();
 				}
 			}
+			/* do not take `_auto_connect_queue_lock' while holding the process lock */
+			lm.release ();
 			reassign_track_numbers ();
 		}
 	}