papermc/CraftBukkit-Patches/0015-Alternate-sync-free-but-safe-chunk-reference-cache.patch

From c5f8d8c747887ce77e775f45c3941d10d05c8147 Mon Sep 17 00:00:00 2001
From: Mike Primm <mike@primmhome.com>
Date: Wed, 16 Jan 2013 15:27:22 -0600
Subject: [PATCH] Alternate, sync-free-but-safe chunk reference cache


diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index a2d1447..3038f80 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -293,15 +293,13 @@ public abstract class World implements IBlockAccess {
 
     // CraftBukkit start
     public Chunk getChunkAt(int i, int j) {
-        Chunk result = null;
-        synchronized (this.chunkLock) {
-            if (this.lastChunkAccessed == null || this.lastXAccessed != i || this.lastZAccessed != j) {
-                this.lastChunkAccessed = this.chunkProvider.getOrCreateChunk(i, j);
-                this.lastXAccessed = i;
-                this.lastZAccessed = j;
-            }
-            result = this.lastChunkAccessed;
+        //synchronized (this.chunkLock) {
+        Chunk result = this.lastChunkAccessed; // Exploit fact that read is atomic 
+        if (result == null || result.x != i || result.z != j) {
+            result = this.chunkProvider.getOrCreateChunk(i, j);
+            this.lastChunkAccessed = result; // Exploit fact that write is atomic
         }
+        //}
         return result;
     }
     // CraftBukkit end
-- 
1.8.1.2