Ensure chunks never load async

Force operation to main thread if it occurs async

Spigot-Server-Patches/0004-MC-Utils.patch

@@ -1,4 +1,4 @@
-From e4c4535575c0397de1e8a388e09428dd60947d13 Mon Sep 17 00:00:00 2001
+From 9e9204318a93e93baf42cab944f182a7d8c38d78 Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Mon, 28 Mar 2016 20:55:47 -0400
 Subject: [PATCH] MC Utils
@@ -7,18 +7,22 @@ Collection of utils to help reduce NMS diff
 
 diff --git a/src/main/java/net/minecraft/server/MCUtil.java b/src/main/java/net/minecraft/server/MCUtil.java
 new file mode 100644
-index 0000000..bcc8ee7
+index 0000000..f059bc2
 --- /dev/null
 +++ b/src/main/java/net/minecraft/server/MCUtil.java
-@@ -0,0 +1,154 @@
+@@ -0,0 +1,185 @@
 +package net.minecraft.server;
 +
 +import com.google.common.util.concurrent.ThreadFactoryBuilder;
 +import org.bukkit.Location;
++import org.bukkit.craftbukkit.util.Waitable;
++import org.spigotmc.AsyncCatcher;
 +
 +import javax.annotation.Nullable;
++import java.util.concurrent.ExecutionException;
 +import java.util.concurrent.Executor;
 +import java.util.concurrent.Executors;
++import java.util.function.Supplier;
 +import java.util.regex.Pattern;
 +
 +public final class MCUtil {
@@ -38,6 +42,33 @@ index 0000000..bcc8ee7
 +    }
 +
 +    /**
++     * Ensures the target code is running on the main thread
++     * @param reason
++     * @param run
++     * @param <T>
++     * @return
++     */
++    public static <T> T ensureMain(String reason, Supplier<T> run) {
++        if (AsyncCatcher.enabled && Thread.currentThread() != MinecraftServer.getServer().primaryThread) {
++            new IllegalStateException( "Asynchronous " + reason + "! Blocking thread until it returns ").printStackTrace();
++            Waitable<T> wait = new Waitable<T>() {
++                @Override
++                protected T evaluate() {
++                    return run.get();
++                }
++            };
++            MinecraftServer.getServer().processQueue.add(wait);
++            try {
++                return wait.get();
++            } catch (InterruptedException | ExecutionException e) {
++                e.printStackTrace();
++            }
++            return null;
++        }
++        return run.get();
++    }
++
++    /**
 +     * Calculates distance between 2 entities
 +     * @param e1
 +     * @param e2
@@ -206,5 +237,5 @@ index 256614d..e86ca6c 100644
  
      public NBTTagList() {}
 -- 
-2.8.2
+2.7.4 (Apple Git-66)
 

Spigot-Server-Patches/0160-Ensure-Chunks-never-ever-load-async.patch

@@ -0,0 +1,46 @@
+From fe9ff05b1c9d84e8894f5034991ebdb21d35e783 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Fri, 27 May 2016 21:41:26 -0400
+Subject: [PATCH] Ensure Chunks never ever load async
+
+Safely pushes the operation to main thread, then back to the posting thread
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/chunkio/ChunkIOExecutor.java b/src/main/java/org/bukkit/craftbukkit/chunkio/ChunkIOExecutor.java
+index 7b7a3d0..9aaca21 100644
+--- a/src/main/java/org/bukkit/craftbukkit/chunkio/ChunkIOExecutor.java
++++ b/src/main/java/org/bukkit/craftbukkit/chunkio/ChunkIOExecutor.java
+@@ -4,6 +4,7 @@ import com.destroystokyo.paper.PaperConfig;
+ import net.minecraft.server.Chunk;
+ import net.minecraft.server.ChunkProviderServer;
+ import net.minecraft.server.ChunkRegionLoader;
++import net.minecraft.server.MCUtil; // Paper
+ import net.minecraft.server.World;
+ import org.bukkit.craftbukkit.util.AsynchronousExecutor;
+ 
+@@ -14,7 +15,7 @@ public class ChunkIOExecutor {
+     private static final AsynchronousExecutor<QueuedChunk, Chunk, Runnable, RuntimeException> instance = new AsynchronousExecutor<QueuedChunk, Chunk, Runnable, RuntimeException>(new ChunkIOProvider(), BASE_THREADS);
+ 
+     public static Chunk syncChunkLoad(World world, ChunkRegionLoader loader, ChunkProviderServer provider, int x, int z) {
+-        return instance.getSkipQueue(new QueuedChunk(x, z, loader, world, provider));
++        return MCUtil.ensureMain("Async Chunk Load", () -> instance.getSkipQueue(new QueuedChunk(x, z, loader, world, provider))); // Paper
+     }
+ 
+     public static void queueChunkLoad(World world, ChunkRegionLoader loader, ChunkProviderServer provider, int x, int z, Runnable runnable) {
+diff --git a/src/main/java/org/bukkit/craftbukkit/chunkio/ChunkIOProvider.java b/src/main/java/org/bukkit/craftbukkit/chunkio/ChunkIOProvider.java
+index 7752b50..4d2b371 100644
+--- a/src/main/java/org/bukkit/craftbukkit/chunkio/ChunkIOProvider.java
++++ b/src/main/java/org/bukkit/craftbukkit/chunkio/ChunkIOProvider.java
+@@ -32,8 +32,8 @@ class ChunkIOProvider implements AsynchronousExecutor.CallBackProvider<QueuedChu
+ 
+     // sync stuff
+     public void callStage2(QueuedChunk queuedChunk, Chunk chunk) throws RuntimeException {
+-        if (chunk == null) {
+-            // If the chunk loading failed just do it synchronously (may generate)
++        if (chunk == null || queuedChunk.provider.chunks.containsKey(ChunkCoordIntPair.a(queuedChunk.x, queuedChunk.z))) { // Paper - also call original if it was already loaded
++            // If the chunk loading failed (or was already loaded for some reason) just do it synchronously (may generate)
+             queuedChunk.provider.originalGetChunkAt(queuedChunk.x, queuedChunk.z);
+             return;
+         }
+-- 
+2.7.4 (Apple Git-66)
+