From eb3045e769eb99754c6ea414590e4734df4f9683 Mon Sep 17 00:00:00 2001
From: Paul Hebble <pjhebble@gmail.com>
Date: Wed, 27 Sep 2023 22:52:34 -0500
Subject: [PATCH] Make tag index thread-safe

---
 Core/Registry/Registry.cs | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/Core/Registry/Registry.cs b/Core/Registry/Registry.cs
index 5f472cdc9d..3d3c03e580 100644
--- a/Core/Registry/Registry.cs
+++ b/Core/Registry/Registry.cs
@@ -712,9 +712,12 @@ public Dictionary<string, ModuleTag> Tags
         {
             get
             {
-                if (tags == null)
+                lock (tagMutex)
                 {
-                    BuildTagIndex();
+                    if (tags == null)
+                    {
+                        BuildTagIndex();
+                    }
                 }
                 return tags;
             }
@@ -725,14 +728,19 @@ public HashSet<string> Untagged
         {
             get
             {
-                if (untagged == null)
+                lock (tagMutex)
                 {
-                    BuildTagIndex();
+                    if (untagged == null)
+                    {
+                        BuildTagIndex();
+                    }
                 }
                 return untagged;
             }
         }
 
+        private object tagMutex = new object();
+
         /// <summary>
         /// Assemble a mapping from tags to modules
         /// </summary>