0085-Remove-DataWatcher-Locking.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sat, 18 Feb 2023 11:59:04 -0300
Subject: [PATCH] Remove DataWatcher Locking

The lock in DataWatcher is used to prevent concurrent modifications,
however any modifications to this map only occur on initialization of
an Entity in its constructor.

Every other access is through a readlock, which allows the threads to
pass if there is no thread holding the writelock.

Since the writelock is only obtained in the constructor of the Entity,
the further readlocks are actually useless.

diff --git a/src/main/java/net/minecraft/server/DataWatcher.java b/src/main/java/net/minecraft/server/DataWatcher.java
index dec091e7311056650dd03a980b2c4aa8299fac4b..518e8f379d690b1f1b4d2374c875dd3dae22360e 100644
--- a/src/main/java/net/minecraft/server/DataWatcher.java
+++ b/src/main/java/net/minecraft/server/DataWatcher.java
@@ -23,13 +23,15 @@ public class DataWatcher {
     private final Map<Integer, DataWatcher.WatchableObject> d = gnu.trove.TDecorators.wrap( dataValues );
     // Spigot End
     private boolean e;
-    private ReadWriteLock f = new ReentrantReadWriteLock();
+    // private ReadWriteLock f = new ReentrantReadWriteLock(); // PandaSpigot - Remove DataWatcher Locking
 
     public DataWatcher(Entity entity) {
         this.a = entity;
     }
 
+    boolean registrationLocked; // PandaSpigot
     public <T> void a(int i, T t0) {
+        if (registrationLocked) throw new IllegalStateException("Registering datawatcher object after entity initialization"); // PandaSpigot
         int integer = classToId.get(t0.getClass()); // Spigot
 
         if (integer == -1) { // Spigot
@@ -41,9 +43,9 @@ public class DataWatcher {
         } else {
             DataWatcher.WatchableObject datawatcher_watchableobject = new DataWatcher.WatchableObject(integer, i, t0); // Spigot
 
-            this.f.writeLock().lock();
+            // this.f.writeLock().lock(); // PandaSpigot
             this.dataValues.put(i, datawatcher_watchableobject); // Spigot
-            this.f.writeLock().unlock();
+            // this.f.writeLock().unlock(); // PandaSpigot
             this.b = false;
         }
     }
@@ -51,9 +53,9 @@ public class DataWatcher {
     public void add(int i, int j) {
         DataWatcher.WatchableObject datawatcher_watchableobject = new DataWatcher.WatchableObject(j, i, (Object) null);
 
-        this.f.writeLock().lock();
+        // this.f.writeLock().lock(); // PandaSpigot
         this.dataValues.put(i, datawatcher_watchableobject); // Spigot
-        this.f.writeLock().unlock();
+        // this.f.writeLock().unlock(); // PandaSpigot
         this.b = false;
     }
 
@@ -82,6 +84,8 @@ public class DataWatcher {
     }
 
     private DataWatcher.WatchableObject j(int i) {
+        // PandaSpigot start - Remove DataWatcher Locking
+        /*
         this.f.readLock().lock();
 
         DataWatcher.WatchableObject datawatcher_watchableobject;
@@ -98,6 +102,9 @@ public class DataWatcher {
 
         this.f.readLock().unlock();
         return datawatcher_watchableobject;
+        */
+        return (WatchableObject) this.dataValues.get(i);
+        // PandaSpigot end
     }
 
     public Vector3f h(int i) {
@@ -143,7 +150,7 @@ public class DataWatcher {
         ArrayList arraylist = null;
 
         if (this.e) {
-            this.f.readLock().lock();
+            // this.f.readLock().lock(); // PandaSpigot
             Iterator iterator = this.dataValues.valueCollection().iterator(); // Spigot
 
             while (iterator.hasNext()) {
@@ -170,7 +177,7 @@ public class DataWatcher {
                 }
             }
 
-            this.f.readLock().unlock();
+            // this.f.readLock().unlock(); // PandaSpigot
         }
 
         this.e = false;
@@ -178,7 +185,7 @@ public class DataWatcher {
     }
 
     public void a(PacketDataSerializer packetdataserializer) throws IOException {
-        this.f.readLock().lock();
+        // this.f.readLock().lock(); // PandaSpigot
         Iterator iterator = this.dataValues.valueCollection().iterator(); // Spigot
 
         while (iterator.hasNext()) {
@@ -187,14 +194,14 @@ public class DataWatcher {
             a(packetdataserializer, datawatcher_watchableobject);
         }
 
-        this.f.readLock().unlock();
+        // this.f.readLock().unlock(); // PandaSpigot
         packetdataserializer.writeByte(127);
     }
 
     public List<DataWatcher.WatchableObject> c() {
         ArrayList arraylist = Lists.newArrayList(); // Spigot
 
-        this.f.readLock().lock();
+        // this.f.readLock().lock(); // PandaSpigot
 
         arraylist.addAll(this.dataValues.valueCollection()); // Spigot
         // Spigot start - copy ItemStacks to prevent ConcurrentModificationExceptions
@@ -213,7 +220,7 @@ public class DataWatcher {
         }
         // Spigot end
 
-        this.f.readLock().unlock();
+        // this.f.readLock().unlock(); // PandaSpigot
         return arraylist;
     }
 
diff --git a/src/main/java/net/minecraft/server/Entity.java b/src/main/java/net/minecraft/server/Entity.java
index c4be7d4e156d8d685ffb2b9fc5f0045ee471ef96..37aae0ccb40e1827f268a88b1a74d288e3f5760d 100644
--- a/src/main/java/net/minecraft/server/Entity.java
+++ b/src/main/java/net/minecraft/server/Entity.java
@@ -197,6 +197,7 @@ public abstract class Entity implements ICommandListener {
         this.datawatcher.a(2, "");
         this.datawatcher.a(4, Byte.valueOf((byte) 0));
         this.h();
+        this.datawatcher.registrationLocked = true; // PandaSpigot
     }
 
     protected abstract void h();