Paper/patches/server/0671-Synchronize-PalettedContainer-instead-of-ReentrantLo.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Fri, 29 May 2020 20:29:02 -0400
Subject: [PATCH] Synchronize PalettedContainer instead of ReentrantLock

Mojang has flaws in their logic about chunks being concurrently
wrote to. So we constantly see crashes around multiple threads writing.

Additionally, java has optimized synchronization so well that its
in many times faster than trying to manage read wrote locks for low
contention situations.

And this is extremely a low contention situation.

diff --git a/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java b/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
index d030baca9dd3c34d14653094c139d853c67ac332..bd003e980ac0fe8c4e4b5df5b4002ae3ada39862 100644
--- a/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
+++ b/src/main/java/net/minecraft/world/level/chunk/PalettedContainer.java
@@ -35,15 +35,15 @@ public class PalettedContainer<T> implements PaletteResize<T> {
     private final ThreadingDetector threadingDetector = new ThreadingDetector("PalettedContainer");
 
     public void acquire() {
-        this.threadingDetector.checkAndLock();
+        // this.threadingDetector.checkAndLock(); // Paper - disable this - use proper synchronization
     }
 
     public void release() {
-        this.threadingDetector.checkAndUnlock();
+        // this.threadingDetector.checkAndUnlock(); // Paper - disable this
     }
 
     public static <T> Codec<PalettedContainer<T>> codec(IdMap<T> idList, Codec<T> entryCodec, PalettedContainer.Strategy provider, T object) {
-        return RecordCodecBuilder.create((instance) -> {
+        return RecordCodecBuilder.<DiscData<T>>create((instance) -> { // Paper - decompile fixes
             return instance.group(entryCodec.mapResult(ExtraCodecs.orElsePartial(object)).listOf().fieldOf("palette").forGetter(PalettedContainer.DiscData::paletteEntries), Codec.LONG_STREAM.optionalFieldOf("data").forGetter(PalettedContainer.DiscData::storage)).apply(instance, PalettedContainer.DiscData::new);
         }).comapFlatMap((serialized) -> {
             return read(idList, provider, serialized);
@@ -85,7 +85,7 @@ public class PalettedContainer<T> implements PaletteResize<T> {
         return data2.palette.idFor(object);
     }
 
-    public T getAndSet(int x, int y, int z, T value) {
+    public synchronized T getAndSet(int x, int y, int z, T value) { // Paper - synchronize
         this.acquire();
 
         Object var5;
@@ -108,7 +108,7 @@ public class PalettedContainer<T> implements PaletteResize<T> {
         return this.data.palette.valueFor(j);
     }
 
-    public void set(int x, int y, int z, T value) {
+    public synchronized void set(int x, int y, int z, T value) { // Paper - synchronize
         this.acquire();
 
         try {
@@ -142,7 +142,7 @@ public class PalettedContainer<T> implements PaletteResize<T> {
         });
     }
 
-    public void read(FriendlyByteBuf buf) {
+    public synchronized void read(FriendlyByteBuf buf) { // Paper - synchronize
         this.acquire();
 
         try {
@@ -157,7 +157,7 @@ public class PalettedContainer<T> implements PaletteResize<T> {
 
     }
 
-    public void write(FriendlyByteBuf buf) {
+    public synchronized void write(FriendlyByteBuf buf) { // Paper - synchronize
         this.acquire();
 
         try {
@@ -168,7 +168,7 @@ public class PalettedContainer<T> implements PaletteResize<T> {
 
     }
 
-    private static <T> DataResult<PalettedContainer<T>> read(IdMap<T> idList, PalettedContainer.Strategy provider, PalettedContainer.DiscData<T> serialized) {
+    private static synchronized <T> DataResult<PalettedContainer<T>> read(IdMap<T> idList, PalettedContainer.Strategy provider, PalettedContainer.DiscData<T> serialized) { // Paper - synchronize
         List<T> list = serialized.paletteEntries();
         int i = provider.size();
         int j = provider.calculateBitsForSerialization(idList, list.size());
@@ -207,7 +207,7 @@ public class PalettedContainer<T> implements PaletteResize<T> {
         return DataResult.success(new PalettedContainer<>(idList, provider, configuration, bitStorage, list));
     }
 
-    private PalettedContainer.DiscData<T> write(IdMap<T> idList, PalettedContainer.Strategy provider) {
+    private synchronized PalettedContainer.DiscData<T> write(IdMap<T> idList, PalettedContainer.Strategy provider) { // Paper - synchronize
         this.acquire();
 
         PalettedContainer.DiscData var12;