From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: wangxyper <wangxyper@163.com>
Date: Sat, 14 Jan 2023 14:23:39 +0800
Subject: [PATCH] Hearse: Remove a lock in ServerChunkCache

Original license: MIT
Original project: https://github.com/NaturalCodeClub/HearseRewrite

diff --git a/src/main/java/net/minecraft/server/level/ServerChunkCache.java b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
index 85c03dc7c1e714fab281374a177cd4c54e97d939..e311724d2e723115bc9549a61e6206a8aed835d8 100644
--- a/src/main/java/net/minecraft/server/level/ServerChunkCache.java
+++ b/src/main/java/net/minecraft/server/level/ServerChunkCache.java
@@ -4,6 +4,9 @@ import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.Lists;
 import com.mojang.datafixers.DataFixer;
 import com.mojang.datafixers.util.Either;
+import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
+import it.unimi.dsi.fastutil.longs.Long2ObjectMaps;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
 import it.unimi.dsi.fastutil.objects.ObjectArraySet;
 import it.unimi.dsi.fastutil.objects.ObjectSet;
 import net.minecraft.Util;
@@ -57,8 +60,7 @@ public class ServerChunkCache extends ChunkSource {
     @VisibleForDebug
     private NaturalSpawner.SpawnState lastSpawnState;
     // Paper start
-    final com.destroystokyo.paper.util.concurrent.WeakSeqLock loadedChunkMapSeqLock = new com.destroystokyo.paper.util.concurrent.WeakSeqLock();
-    final it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap<LevelChunk> loadedChunkMap = new it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap<>(8192, 0.5f);
+    private final Long2ObjectMap<LevelChunk> loadedChunkMap = Long2ObjectMaps.synchronize(new Long2ObjectOpenHashMap<>(8192, 0.5f));
 
     private final LevelChunk[] lastLoadedChunks = new LevelChunk[4 * 4];
     
@@ -70,12 +72,7 @@ public class ServerChunkCache extends ChunkSource {
     }
 
     public void addLoadedChunk(LevelChunk chunk) {
-        this.loadedChunkMapSeqLock.acquireWrite();
-        try {
-            this.loadedChunkMap.put(chunk.coordinateKey, chunk);
-        } finally {
-            this.loadedChunkMapSeqLock.releaseWrite();
-        }
+        this.loadedChunkMap.put(chunk.coordinateKey, chunk);
 
         // rewrite cache if we have to
         // we do this since we also cache null chunks
@@ -85,13 +82,7 @@ public class ServerChunkCache extends ChunkSource {
     }
 
     public void removeLoadedChunk(LevelChunk chunk) {
-        this.loadedChunkMapSeqLock.acquireWrite();
-        try {
-            this.loadedChunkMap.remove(chunk.coordinateKey);
-        } finally {
-            this.loadedChunkMapSeqLock.releaseWrite();
-        }
-
+        this.loadedChunkMap.remove(chunk.coordinateKey);
         // rewrite cache if we have to
         // we do this since we also cache null chunks
         int cacheKey = getChunkCacheKey(chunk.locX, chunk.locZ);
@@ -360,22 +351,7 @@ public class ServerChunkCache extends ChunkSource {
             return this.getChunkAtIfLoadedMainThread(x, z);
         }
 
-        LevelChunk ret = null;
-        long readlock;
-        do {
-            readlock = this.loadedChunkMapSeqLock.acquireRead();
-            try {
-                ret = this.loadedChunkMap.get(k);
-            } catch (Throwable thr) {
-                if (thr instanceof ThreadDeath) {
-                    throw (ThreadDeath)thr;
-                }
-                // re-try, this means a CME occurred...
-                continue;
-            }
-        } while (!this.loadedChunkMapSeqLock.tryReleaseRead(readlock));
-
-        return ret;
+        return this.loadedChunkMap.get(k);
     }
     // Paper end
     // Paper start - async chunk io
@@ -436,7 +412,7 @@ public class ServerChunkCache extends ChunkSource {
                 // 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);
+                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
@@ -495,6 +471,7 @@ public class ServerChunkCache extends ChunkSource {
         // Paper start - add isUrgent - old sig left in place for dirty nms plugins
         return getChunkFutureMainThread(chunkX, chunkZ, leastStatus, create, false);
     }
+
     private CompletableFuture<Either<ChunkAccess, ChunkHolder.ChunkLoadingFailure>> getChunkFutureMainThread(int chunkX, int chunkZ, ChunkStatus leastStatus, boolean create, boolean isUrgent) {
         // Paper start - rewrite chunk system
         io.papermc.paper.util.TickThread.ensureTickThread(this.level, chunkX, chunkZ, "Scheduling chunk load off-main");