Reduce the chance of concurrent Long2ObjectLinkedOpenHashMap issues

common/src/main/java/com/seibel/distanthorizons/common/wrappers/worldGeneration/mimicObject/DhLitWorldGenRegion.java

@@ -21,6 +21,7 @@ package com.seibel.distanthorizons.common.wrappers.worldGeneration.mimicObject;
 
 import java.lang.invoke.MethodHandles;
 import java.util.List;
+import java.util.concurrent.locks.ReentrantLock;
 
 import com.seibel.distanthorizons.common.wrappers.worldGeneration.BatchGenerationEnvironment;
 import com.seibel.distanthorizons.core.logging.DhLoggerBuilder;
@@ -66,6 +67,12 @@ public class DhLitWorldGenRegion extends WorldGenRegion
 	private final List<ChunkAccess> cache;
 	Long2ObjectOpenHashMap<ChunkAccess> chunkMap = new Long2ObjectOpenHashMap<ChunkAccess>();
 	
+	/** 
+	 * Present to reduce the chance that we accidentally break underlying MC code that isn't thread safe, 
+	 * specifically: "it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap.getAndMoveToFirst()"
+	 */
+	ReentrantLock getChunkLock = new ReentrantLock();
+	
 	#if PRE_MC_1_18_2
 	private ChunkPos overrideCenterPos = null;
 	
@@ -90,6 +97,8 @@ public class DhLitWorldGenRegion extends WorldGenRegion
 	#endif
 	#endif
 	
+	
+	
 	public DhLitWorldGenRegion(
 			ServerLevel serverLevel, DummyLightEngine lightEngine,
 			List<ChunkAccess> chunkList, ChunkStatus chunkStatus, int writeRadius,
@@ -104,6 +113,8 @@ public class DhLitWorldGenRegion extends WorldGenRegion
 		this.size = Mth.floor(Math.sqrt(chunkList.size()));
 	}
 	
+	
+	
 	#if POST_MC_1_17_1
 	// Bypass BCLib mixin overrides.
 	@Override
@@ -205,7 +216,16 @@ public class DhLitWorldGenRegion extends WorldGenRegion
 	@Override
 	public ChunkAccess getChunk(int i, int j)
 	{
-		return this.getChunk(i, j, ChunkStatus.EMPTY);
+		try
+		{
+			// lock is to prevent issues with underlying MC code that doesn't support multithreading
+			this.getChunkLock.lock();
+			return this.getChunk(i, j, ChunkStatus.EMPTY);
+		}
+		finally
+		{
+			this.getChunkLock.unlock();
+		}
 	}
 	
 	// Override to ensure no other mod mixins cause skipping the overrided
@@ -213,7 +233,16 @@ public class DhLitWorldGenRegion extends WorldGenRegion
 	@Override
 	public ChunkAccess getChunk(int i, int j, ChunkStatus chunkStatus)
 	{
-		return this.getChunk(i, j, chunkStatus, true);
+		try
+		{
+			// lock is to prevent issues with underlying MC code that doesn't support multithreading
+			this.getChunkLock.lock();
+			return this.getChunk(i, j, chunkStatus, true);
+		}
+		finally
+		{
+			this.getChunkLock.unlock();
+		}
 	}
 	
 	// Use this instead of super.getChunk() to bypass C2ME concurrency checks

common/src/main/java/com/seibel/distanthorizons/common/wrappers/worldGeneration/mimicObject/RegionFileStorageExternalCache.java

@@ -13,21 +13,20 @@ import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.locks.ReentrantLock;
 
 public class RegionFileStorageExternalCache implements AutoCloseable
 {
 	public final RegionFileStorage storage;
 	public static final int MAX_CACHE_SIZE = 16;
 	
-	@Override
-	public void close() throws IOException
-	{
-		RegionFileCache cache;
-		while ((cache = this.regionFileCache.poll()) != null)
-		{
-			cache.file.close();
-		}
-	}
+	/**
+	 * Present to reduce the chance that we accidentally break underlying MC code that isn't thread safe, 
+	 * specifically: "it.unimi.dsi.fastutil.longs.Long2ObjectLinkedOpenHashMap.getAndMoveToFirst()"
+	 */
+	ReentrantLock getRegionFileLock = new ReentrantLock();
+	
+	
 	
 	static class RegionFileCache
 	{
@@ -42,6 +41,8 @@ public class RegionFileStorageExternalCache implements AutoCloseable
 		
 	}
 	
+	
+	
 	public ConcurrentLinkedQueue<RegionFileCache> regionFileCache = new ConcurrentLinkedQueue<>();
 	
 	public RegionFileStorageExternalCache(RegionFileStorage storage) { this.storage = storage; }
@@ -61,6 +62,8 @@ public class RegionFileStorageExternalCache implements AutoCloseable
 			
 			try
 			{
+				this.getRegionFileLock.lock();
+				
 				#if MC_1_16_5 || MC_1_17_1
 				rFile = this.storage.getRegionFile(pos);
 				#else
@@ -85,6 +88,10 @@ public class RegionFileStorageExternalCache implements AutoCloseable
 				}
 				#endif
 			}
+			finally
+			{
+				this.getRegionFileLock.unlock();
+			}
 		}
 		
 		if (retryCount >= maxRetryCount)
@@ -140,7 +147,7 @@ public class RegionFileStorageExternalCache implements AutoCloseable
 	@Nullable
 	public CompoundTag read(ChunkPos pos) throws IOException
 	{
-		RegionFile file = getRegionFile(pos);
+		RegionFile file = this.getRegionFile(pos);
 		if (file == null)
 		{
 			return null;
@@ -162,4 +169,16 @@ public class RegionFileStorageExternalCache implements AutoCloseable
 		}
 	}
 	
+	
+	@Override
+	public void close() throws IOException
+	{
+		RegionFileCache cache;
+		while ((cache = this.regionFileCache.poll()) != null)
+		{
+			cache.file.close();
+		}
+	}
+	
+	
 }

common/src/main/java/com/seibel/distanthorizons/common/wrappers/worldGeneration/step/StepStructureReference.java

@@ -63,7 +63,7 @@ public final class StepStructureReference
 		for (ChunkAccess chunk : chunksToDo)
 		{
 			// System.out.println("StepStructureReference: "+chunk.getPos());
-			environment.params.generator.createReferences(worldGenRegion, tParams.structFeat.forWorldGenRegion(worldGenRegion), chunk);
+			this.environment.params.generator.createReferences(worldGenRegion, tParams.structFeat.forWorldGenRegion(worldGenRegion), chunk);
 		}
 	}
 	

common/src/main/java/com/seibel/distanthorizons/common/wrappers/worldGeneration/step/StepStructureStart.java

@@ -38,7 +38,7 @@ public final class StepStructureStart
 {
 	private static final Logger LOGGER = DhLoggerBuilder.getLogger();
 	private static final ChunkStatus STATUS = ChunkStatus.STRUCTURE_STARTS;
-	private static final ReentrantLock structurePlacementLock = new ReentrantLock();
+	private static final ReentrantLock STRUCTURE_PLACEMENT_LOCK = new ReentrantLock();
 	
 	private final BatchGenerationEnvironment environment;
 	
@@ -96,7 +96,7 @@ public final class StepStructureStart
 				
 				// hopefully this shouldn't cause any performance issues (this step is generally quite quick so hopefully it should be fine)
 				// and should prevent some concurrency issues
-				structurePlacementLock.lock();
+				STRUCTURE_PLACEMENT_LOCK.lock();
 				
 				#if PRE_MC_1_19_2
 				environment.params.generator.createStructures(environment.params.registry, tParams.structFeat, chunk, environment.params.structures,
@@ -140,7 +140,7 @@ public final class StepStructureStart
 				
 				#endif
 				
-				structurePlacementLock.unlock();
+				STRUCTURE_PLACEMENT_LOCK.unlock();
 			}
 		}
 	}