From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Shane Freeder <theboyetronic@gmail.com>
Date: Fri, 3 Sep 2021 15:50:25 +0100
Subject: [PATCH] Do not process entity loads in CraftChunk#getEntities

This re-introduces the issue behind #5872 but fixes #6543
The logic here is generally flawed however somewhat of a nuance,
upstream uses managedBlock which is basically needed to process
the posted entity adds, but, has the side-effect of processing any
chunk loads which has the naunce of stacking up and either causing a
massive performance hit, or can potentially lead the server to crash.

This issue is particularly noticable on paper due to the cumulative efforts
to drastically improve chunk loading speeds which means that there is much more
of a chance that we're about to eat a dirtload of chunk load callbacks, thus
making this issue much more of an issue

diff --git a/src/main/java/org/bukkit/craftbukkit/CraftChunk.java b/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
index 0085a4dd0f0def1ba71342e20aecdd46a3761b02..0cf67d55ab30ab145ffb2ff562c26c47c2e2879e 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
@@ -129,46 +129,6 @@ public class CraftChunk implements Chunk {
             this.getWorld().getChunkAt(x, z); // Transient load for this tick
         }
 
-        PersistentEntitySectionManager<net.minecraft.world.entity.Entity> entityManager = this.getCraftWorld().getHandle().entityManager;
-        long pair = ChunkPos.asLong(x, z);
-
-        if (entityManager.areEntitiesLoaded(pair)) {
-            return getCraftWorld().getHandle().getChunkEntities(this.x, this.z); // Paper - optimise this
-        }
-
-        entityManager.ensureChunkQueuedForLoad(pair); // Start entity loading
-
-        // SPIGOT-6772: Use entity mailbox and re-schedule entities if they get unloaded
-        ProcessorMailbox<Runnable> mailbox = ((EntityStorage) entityManager.permanentStorage).entityDeserializerQueue;
-        BooleanSupplier supplier = () -> {
-            // only execute inbox if our entities are not present
-            if (entityManager.areEntitiesLoaded(pair)) {
-                return true;
-            }
-
-            if (!entityManager.isPending(pair)) {
-                // Our entities got unloaded, this should normally not happen.
-                entityManager.ensureChunkQueuedForLoad(pair); // Re-start entity loading
-            }
-
-            // tick loading inbox, which loads the created entities to the world
-            // (if present)
-            entityManager.tick();
-            // check if our entities are loaded
-            return entityManager.areEntitiesLoaded(pair);
-        };
-
-        // now we wait until the entities are loaded,
-        // the converting from NBT to entity object is done on the main Thread which is why we wait
-        while (!supplier.getAsBoolean()) {
-            if (mailbox.size() != 0) {
-                mailbox.run();
-            } else {
-                Thread.yield();
-                LockSupport.parkNanos("waiting for entity loading", 100000L);
-            }
-        }
-
         return getCraftWorld().getHandle().getChunkEntities(this.x, this.z); // Paper - optimise this
     }