From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Mon, 1 Feb 2021 15:35:14 -0800
Subject: [PATCH] Fix chunks refusing to unload at low TPS

The full chunk future is appended to the chunk save future, but
when moving to unloaded ticket level it is not being completed with
the empty chunk access, so the chunk save must wait for the full
chunk future to complete. We can simply schedule to the immediate
executor to get this effect, rather than the main mailbox.

diff --git a/src/main/java/net/minecraft/server/level/ChunkMap.java b/src/main/java/net/minecraft/server/level/ChunkMap.java
index d53ff732a503eab3aea0384475f8a56d3076828d..971a31641ec33a80f45e507944fa4cd90bfc466a 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -1300,9 +1300,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
 
                 return chunk;
             });
-        }, (runnable) -> {
-            this.mainThreadMailbox.tell(ChunkTaskPriorityQueueSorter.message(holder, runnable));
-        });
+        }, this.mainThreadExecutor); // Paper - queue to execute immediately so this doesn't delay chunk unloading
     }
 
     public int getTickingGenerated() {