Paper/patches/server/0737-Fix-chunks-refusing-to-unload-at-low-TPS.patch

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 5261c7a44200e2cc191b67900c7771ca31fb33df..16350310a235c321e48c29fbace2969b43778bf5 100644
--- a/src/main/java/net/minecraft/server/level/ChunkMap.java
+++ b/src/main/java/net/minecraft/server/level/ChunkMap.java
@@ -1302,9 +1302,7 @@ public class ChunkMap extends ChunkStorage implements ChunkHolder.PlayerProvider
                     this.playerLoadedChunk(entityplayer, mutableobject, chunk);
                 });
             });
-        }, (runnable) -> {
-            this.mainThreadMailbox.tell(ChunkTaskPriorityQueueSorter.message(holder, () -> ChunkMap.this.chunkLoadConversionCallbackExecutor.execute(runnable))); // Paper - delay running Chunk post processing until outside of the sorter to prevent a deadlock scenario when post processing causes another chunk request.
-        });
+        }, this.mainThreadExecutor); // Paper - queue to execute immediately so this doesn't delay chunk unloading
         return completablefuture1;
     }