From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: wangxyper <wangxyper@163.com>
Date: Thu, 19 Jan 2023 10:03:10 +0800
Subject: [PATCH] Hearse: Add locks when calling getChunk in worker thread

Original license: MIT
Original project: https://github.com/Era4FunMC/Hearse

diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index e311724d2e723115bc9549a61e6206a8aed835d8..b151339cc56418f82f9b75b39b8fc6ab6686993e 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -1,5 +1,6 @@
 package net.minecraft.server.level;
 
+import co.earthme.hearse.concurrent.thread.Worker;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Lists;
 import com.mojang.datafixers.DataFixer;
@@ -377,57 +378,68 @@ public class ServerChunkCache extends ChunkSource {
     }
     // Paper end - async chunk io
 
+    private final Object workerGetChunkLock = new Object();
+
     @Nullable
     @Override
     public ChunkAccess getChunk(int x, int z, ChunkStatus leastStatus, boolean create) {
-        final int x1 = x; final int z1 = z; // Paper - conflict on variable change
         if (!io.papermc.paper.util.TickThread.isTickThread()) { // Paper - rewrite chunk system
             return (ChunkAccess) CompletableFuture.supplyAsync(() -> {
                 return this.getChunk(x, z, leastStatus, create);
             }, this.mainThreadProcessor).join();
         } else {
-            // Paper start - optimise for loaded chunks
-            LevelChunk ifLoaded = this.getChunkAtIfLoadedMainThread(x, z);
-            if (ifLoaded != null) {
-                return ifLoaded;
+            if (Thread.currentThread() instanceof Worker){
+                synchronized (this.workerGetChunkLock){
+                    return this.getChunkUnsafe(x,z,leastStatus,create);
+                }
             }
-            // Paper end
-            //ProfilerFiller gameprofilerfiller = this.level.getProfiler(); // Purpur
+            return this.getChunkUnsafe(x,z,leastStatus,create);
+        }
+    }
 
-            //gameprofilerfiller.incrementCounter("getChunk"); // Purpur
-            long k = ChunkPos.asLong(x, z);
+    private ChunkAccess getChunkUnsafe(int x,int z,ChunkStatus leastStatus,boolean create){
+        final int x1 = x; final int z1 = z; // Paper - conflict on variable change
+        // Paper start - optimise for loaded chunks
+        LevelChunk ifLoaded = this.getChunkAtIfLoadedMainThread(x, z);
+        if (ifLoaded != null) {
+            return ifLoaded;
+        }
+        // Paper end
+        //ProfilerFiller gameprofilerfiller = this.level.getProfiler(); // Purpur
 
-            ChunkAccess ichunkaccess;
+        //gameprofilerfiller.incrementCounter("getChunk"); // Purpur
+        long k = ChunkPos.asLong(x, z);
 
-            // Paper - rewrite chunk system - there are no correct callbacks to remove items from cache in the new chunk system
+        ChunkAccess ichunkaccess;
 
-            //gameprofilerfiller.incrementCounter("getChunkCacheMiss"); // Purpur
-            CompletableFuture<Either<ChunkAccess, ChunkHolder.ChunkLoadingFailure>> completablefuture = this.getChunkFutureMainThread(x, z, leastStatus, create, true); // Paper
-            ServerChunkCache.MainThreadExecutor chunkproviderserver_b = this.mainThreadProcessor;
+        // Paper - rewrite chunk system - there are no correct callbacks to remove items from cache in the new chunk system
 
-            Objects.requireNonNull(completablefuture);
-            if (!completablefuture.isDone()) { // Paper
-                // Paper start - async chunk io/loading
-                io.papermc.paper.chunk.system.scheduling.ChunkTaskScheduler.pushChunkWait(this.level, x1, z1); // Paper - rewrite chunk system
-                // Paper end
-                com.destroystokyo.paper.io.SyncLoadFinder.logSyncLoad(this.level, x1, z1); // Paper - sync load info
-                //this.level.timings.syncChunkLoad.startTiming(); // Paper // Purpur
-                chunkproviderserver_b.managedBlock(completablefuture::isDone);
-                io.papermc.paper.chunk.system.scheduling.ChunkTaskScheduler.popChunkWait(); // Paper - async chunk debug  // Paper - rewrite chunk system
-                //this.level.timings.syncChunkLoad.stopTiming(); // Paper // Purpur
-            } // Paper
-            ichunkaccess = (ChunkAccess) ((Either) completablefuture.join()).map((ichunkaccess1) -> {
-                return ichunkaccess1;
-            }, (playerchunk_failure) -> {
-                if (create) {
-                    throw (IllegalStateException) Util.pauseInIde(new IllegalStateException("Chunk not there when requested: " + playerchunk_failure));
-                } else {
-                    return null;
-                }
-            });
-            this.storeInCache(k, ichunkaccess, leastStatus);
-            return ichunkaccess;
-        }
+        //gameprofilerfiller.incrementCounter("getChunkCacheMiss"); // Purpur
+        CompletableFuture<Either<ChunkAccess, ChunkHolder.ChunkLoadingFailure>> completablefuture = this.getChunkFutureMainThread(x, z, leastStatus, create, true); // Paper
+        ServerChunkCache.MainThreadExecutor chunkproviderserver_b = this.mainThreadProcessor;
+
+        Objects.requireNonNull(completablefuture);
+        if (!completablefuture.isDone()) { // Paper
+            // Paper start - async chunk io/loading
+            io.papermc.paper.chunk.system.scheduling.ChunkTaskScheduler.pushChunkWait(this.level, x1, z1); // Paper - rewrite chunk system
+            // Paper end
+            com.destroystokyo.paper.io.SyncLoadFinder.logSyncLoad(this.level, x1, z1); // Paper - sync load info
+            //this.level.timings.syncChunkLoad.startTiming(); // Paper // Purpur
+            chunkproviderserver_b.managedBlock(completablefuture::isDone);
+            io.papermc.paper.chunk.system.scheduling.ChunkTaskScheduler.popChunkWait(); // Paper - async chunk debug  // Paper - rewrite chunk system
+            //this.level.timings.syncChunkLoad.stopTiming(); // Paper // Purpur
+        } // Paper
+        ichunkaccess = (ChunkAccess) ((Either) completablefuture.join()).map((ichunkaccess1) -> {
+            return ichunkaccess1;
+        }, (playerchunk_failure) -> {
+            if (create) {
+                throw (IllegalStateException) Util.pauseInIde(new IllegalStateException("Chunk not there when requested: " + playerchunk_failure));
+            } else {
+                return null;
+            }
+        });
+        this.storeInCache(k, ichunkaccess, leastStatus);
+        return ichunkaccess;
     }
 
     @Nullable
@@ -440,6 +452,7 @@ public class ServerChunkCache extends ChunkSource {
         }
     }
 
+
     private void clearCache() {
         Arrays.fill(this.lastChunkPos, ChunkPos.INVALID_CHUNK_POS);
         Arrays.fill(this.lastChunkStatus, (Object) null);