Remove deadlock risk in firing async events

The PluginManager incorrectly used synchronization on firing any event
that was marked as synchronous.

This synchronized did not even protect any concurrency risk as
handlers were already thread safe in terms of mutations during event
dispatch.

The way it was used, has commonly led to deadlocks on the server,
which results in a hard crash.

This change removes the synchronize and adds some protection around enable/disable

Spigot-API-Patches/Add-source-block-to-BlockPhysicsEvent.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Add source block to BlockPhysicsEvent
 
 
 diff --git a/src/main/java/org/bukkit/event/block/BlockPhysicsEvent.java b/src/main/java/org/bukkit/event/block/BlockPhysicsEvent.java
-index 01a545b4..d17e05ac 100644
+index 01a545b42..57568cd02 100644
 --- a/src/main/java/org/bukkit/event/block/BlockPhysicsEvent.java
 +++ b/src/main/java/org/bukkit/event/block/BlockPhysicsEvent.java
 @@ -0,0 +0,0 @@ public class BlockPhysicsEvent extends BlockEvent implements Cancellable {

Spigot-API-Patches/Remove-deadlock-risk-in-firing-async-events.patch

@@ -0,0 +1,81 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Sun, 9 Sep 2018 00:32:05 -0400
+Subject: [PATCH] Remove deadlock risk in firing async events
+
+The PluginManager incorrectly used synchronization on firing any event
+that was marked as synchronous.
+
+This synchronized did not even protect any concurrency risk as
+handlers were already thread safe in terms of mutations during event
+dispatch.
+
+The way it was used, has commonly led to deadlocks on the server,
+which results in a hard crash.
+
+This change removes the synchronize and adds some protection around enable/disable
+
+diff --git a/src/main/java/org/bukkit/plugin/SimplePluginManager.java b/src/main/java/org/bukkit/plugin/SimplePluginManager.java
+index cb2b0b9cb..a7dd902fb 100644
+--- a/src/main/java/org/bukkit/plugin/SimplePluginManager.java
++++ b/src/main/java/org/bukkit/plugin/SimplePluginManager.java
+@@ -0,0 +0,0 @@ public final class SimplePluginManager implements PluginManager {
+      * @param plugin Plugin to check
+      * @return true if the plugin is enabled, otherwise false
+      */
+-    public boolean isPluginEnabled(Plugin plugin) {
++    public synchronized boolean isPluginEnabled(Plugin plugin) { // Paper - synchronize
+         if ((plugin != null) && (plugins.contains(plugin))) {
+             return plugin.isEnabled();
+         } else {
+@@ -0,0 +0,0 @@ public final class SimplePluginManager implements PluginManager {
+         }
+     }
+ 
+-    public void enablePlugin(final Plugin plugin) {
++    public synchronized void enablePlugin(final Plugin plugin) { // Paper - synchronize
+         if (!plugin.isEnabled()) {
+             List<Command> pluginCommands = PluginCommandYamlParser.parse(plugin);
+ 
+@@ -0,0 +0,0 @@ public final class SimplePluginManager implements PluginManager {
+         disablePlugin(plugin, false);
+     }
+ 
+-    public void disablePlugin(final Plugin plugin, boolean closeClassloader) {
++    public synchronized void disablePlugin(final Plugin plugin, boolean closeClassloader) { // Paper - synchronize
+         // Paper end - close Classloader on disable
+         if (plugin.isEnabled()) {
+             try {
+@@ -0,0 +0,0 @@ public final class SimplePluginManager implements PluginManager {
+             defaultPerms.get(false).clear();
+         }
+     }
++    private void fireEvent(Event event) { callEvent(event); } // Paper - support old method incase plugin uses reflection
+ 
+     /**
+      * Calls an event with the given details.
+@@ -0,0 +0,0 @@ public final class SimplePluginManager implements PluginManager {
+      * @param event Event details
+      */
+     public void callEvent(Event event) {
+-        if (event.isAsynchronous()) {
+-            if (Thread.holdsLock(this)) {
+-                throw new IllegalStateException(event.getEventName() + " cannot be triggered asynchronously from inside synchronized code.");
+-            }
+-            if (server.isPrimaryThread()) {
+-                throw new IllegalStateException(event.getEventName() + " cannot be triggered asynchronously from primary server thread.");
+-            }
+-            fireEvent(event);
+-        } else {
+-            synchronized (this) {
+-                fireEvent(event);
+-            }
+-        }
+-    }
+-
+-    private void fireEvent(Event event) {
++        // Paper - replace callEvent by merging to below method
+         HandlerList handlers = event.getHandlers();
+         RegisteredListener[] listeners = handlers.getRegisteredListeners();
+ 
+--

Spigot-API-Patches/isChunkGenerated-API.patch

@@ -6,7 +6,7 @@ Subject: [PATCH] isChunkGenerated API
 Resolves #1329
 
 diff --git a/src/main/java/org/bukkit/Location.java b/src/main/java/org/bukkit/Location.java
-index 7e1ee875..9457832b 100644
+index 7e1ee875e..9457832bc 100644
 --- a/src/main/java/org/bukkit/Location.java
 +++ b/src/main/java/org/bukkit/Location.java
 @@ -0,0 +0,0 @@ import org.bukkit.util.NumberConversions;
@@ -34,7 +34,7 @@ index 7e1ee875..9457832b 100644
      /**
       * Sets the position of this Location and returns itself
 diff --git a/src/main/java/org/bukkit/World.java b/src/main/java/org/bukkit/World.java
-index a6facc4b..d5058634 100644
+index a6facc4b0..d50586349 100644
 --- a/src/main/java/org/bukkit/World.java
 +++ b/src/main/java/org/bukkit/World.java
 @@ -0,0 +0,0 @@ public interface World extends PluginMessageRecipient, Metadatable {

Spigot-Server-Patches/Add-source-block-to-BlockPhysicsEvent.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Add source block to BlockPhysicsEvent
 
 
 diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
-index 04d0fa1d..64d75934 100644
+index 04d0fa1df9..64d75934bc 100644
 --- a/src/main/java/net/minecraft/server/World.java
 +++ b/src/main/java/net/minecraft/server/World.java
 @@ -0,0 +0,0 @@ public abstract class World implements IBlockAccess {

Spigot-Server-Patches/Anti-Xray.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Anti-Xray
 
 
 diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
-index 646620d0c..4d30cdbc8 100644
+index 646620d0c2..4d30cdbc8b 100644
 --- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
 +++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
 @@ -0,0 +0,0 @@
@@ -49,7 +49,7 @@ index 646620d0c..4d30cdbc8 100644
  }
 diff --git a/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockController.java b/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockController.java
 new file mode 100644
-index 000000000..6833cfad2
+index 0000000000..6833cfad25
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockController.java
 @@ -0,0 +0,0 @@
@@ -91,7 +91,7 @@ index 000000000..6833cfad2
 +}
 diff --git a/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockControllerAntiXray.java b/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockControllerAntiXray.java
 new file mode 100644
-index 000000000..2dc0655a9
+index 0000000000..2dc0655a93
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/antixray/ChunkPacketBlockControllerAntiXray.java
 @@ -0,0 +0,0 @@
@@ -737,7 +737,7 @@ index 000000000..2dc0655a9
 +}
 diff --git a/src/main/java/com/destroystokyo/paper/antixray/DataBitsReader.java b/src/main/java/com/destroystokyo/paper/antixray/DataBitsReader.java
 new file mode 100644
-index 000000000..92399318c
+index 0000000000..92399318cd
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/antixray/DataBitsReader.java
 @@ -0,0 +0,0 @@
@@ -799,7 +799,7 @@ index 000000000..92399318c
 +}
 diff --git a/src/main/java/com/destroystokyo/paper/antixray/DataBitsWriter.java b/src/main/java/com/destroystokyo/paper/antixray/DataBitsWriter.java
 new file mode 100644
-index 000000000..aca0b9d71
+index 0000000000..aca0b9d719
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/antixray/DataBitsWriter.java
 @@ -0,0 +0,0 @@
@@ -889,7 +889,7 @@ index 000000000..aca0b9d71
 +}
 diff --git a/src/main/java/com/destroystokyo/paper/antixray/PacketPlayOutMapChunkInfo.java b/src/main/java/com/destroystokyo/paper/antixray/PacketPlayOutMapChunkInfo.java
 new file mode 100644
-index 000000000..0bd269a07
+index 0000000000..0bd269a079
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/antixray/PacketPlayOutMapChunkInfo.java
 @@ -0,0 +0,0 @@
@@ -975,7 +975,7 @@ index 000000000..0bd269a07
 +}
 diff --git a/src/main/java/com/destroystokyo/paper/antixray/PacketPlayOutMapChunkInfoAntiXray.java b/src/main/java/com/destroystokyo/paper/antixray/PacketPlayOutMapChunkInfoAntiXray.java
 new file mode 100644
-index 000000000..8ea2beb59
+index 0000000000..8ea2beb597
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/antixray/PacketPlayOutMapChunkInfoAntiXray.java
 @@ -0,0 +0,0 @@
@@ -1008,7 +1008,7 @@ index 000000000..8ea2beb59
 +    }
 +}
 diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
-index 27a36b2b0..cb33cf902 100644
+index 663a41e9e7..0226b96f30 100644
 --- a/src/main/java/net/minecraft/server/Chunk.java
 +++ b/src/main/java/net/minecraft/server/Chunk.java
 @@ -0,0 +0,0 @@ public class Chunk {
@@ -1039,7 +1039,7 @@ index 27a36b2b0..cb33cf902 100644
              this.initLighting();
          }
 diff --git a/src/main/java/net/minecraft/server/ChunkRegionLoader.java b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
-index 14f88e91d..bcce5e8b7 100644
+index 14f88e91db..bcce5e8b7e 100644
 --- a/src/main/java/net/minecraft/server/ChunkRegionLoader.java
 +++ b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
 @@ -0,0 +0,0 @@ public class ChunkRegionLoader implements IChunkLoader, IAsyncChunkSaver {
@@ -1052,7 +1052,7 @@ index 14f88e91d..bcce5e8b7 100644
              NibbleArray nibblearray = new NibbleArray(nbttagcompound1.getByteArray("Data"));
              NibbleArray nibblearray1 = nbttagcompound1.hasKeyOfType("Add", 7) ? new NibbleArray(nbttagcompound1.getByteArray("Add")) : null;
 diff --git a/src/main/java/net/minecraft/server/ChunkSection.java b/src/main/java/net/minecraft/server/ChunkSection.java
-index afdc4a779..aae227fdb 100644
+index afdc4a779a..aae227fdb0 100644
 --- a/src/main/java/net/minecraft/server/ChunkSection.java
 +++ b/src/main/java/net/minecraft/server/ChunkSection.java
 @@ -0,0 +0,0 @@ public class ChunkSection {
@@ -1092,7 +1092,7 @@ index afdc4a779..aae227fdb 100644
              int xx = i & 15;
              int yy = (i >> 8) & 15;
 diff --git a/src/main/java/net/minecraft/server/DataBits.java b/src/main/java/net/minecraft/server/DataBits.java
-index fa0fd8a9c..401dc7cdc 100644
+index fa0fd8a9c8..401dc7cdc5 100644
 --- a/src/main/java/net/minecraft/server/DataBits.java
 +++ b/src/main/java/net/minecraft/server/DataBits.java
 @@ -0,0 +0,0 @@ public class DataBits {
@@ -1104,7 +1104,7 @@ index fa0fd8a9c..401dc7cdc 100644
          return this.a;
      }
 diff --git a/src/main/java/net/minecraft/server/DataPalette.java b/src/main/java/net/minecraft/server/DataPalette.java
-index 5765b2588..d522611ec 100644
+index 5765b25888..d522611ecb 100644
 --- a/src/main/java/net/minecraft/server/DataPalette.java
 +++ b/src/main/java/net/minecraft/server/DataPalette.java
 @@ -0,0 +0,0 @@ import javax.annotation.Nullable;
@@ -1119,7 +1119,7 @@ index 5765b2588..d522611ec 100644
      IBlockData a(int i);
  
 diff --git a/src/main/java/net/minecraft/server/DataPaletteBlock.java b/src/main/java/net/minecraft/server/DataPaletteBlock.java
-index 2cb462b8e..67784b4a6 100644
+index 2cb462b8e3..67784b4a67 100644
 --- a/src/main/java/net/minecraft/server/DataPaletteBlock.java
 +++ b/src/main/java/net/minecraft/server/DataPaletteBlock.java
 @@ -0,0 +0,0 @@ package net.minecraft.server;
@@ -1227,7 +1227,7 @@ index 2cb462b8e..67784b4a6 100644
      }
  
 diff --git a/src/main/java/net/minecraft/server/EntityFallingBlock.java b/src/main/java/net/minecraft/server/EntityFallingBlock.java
-index d0b67d8fd..eeaa625d2 100644
+index d0b67d8fd6..eeaa625d2f 100644
 --- a/src/main/java/net/minecraft/server/EntityFallingBlock.java
 +++ b/src/main/java/net/minecraft/server/EntityFallingBlock.java
 @@ -0,0 +0,0 @@ public class EntityFallingBlock extends Entity {
@@ -1247,7 +1247,7 @@ index d0b67d8fd..eeaa625d2 100644
                                  if (block instanceof BlockFalling) {
                                      ((BlockFalling) block).a(this.world, blockposition, this.block, iblockdata);
 diff --git a/src/main/java/net/minecraft/server/Explosion.java b/src/main/java/net/minecraft/server/Explosion.java
-index e148901e5..61fbdeb6a 100644
+index e148901e53..61fbdeb6ac 100644
 --- a/src/main/java/net/minecraft/server/Explosion.java
 +++ b/src/main/java/net/minecraft/server/Explosion.java
 @@ -0,0 +0,0 @@ public class Explosion {
@@ -1259,7 +1259,7 @@ index e148901e5..61fbdeb6a 100644
                  if (flag) {
                      double d0 = (double) ((float) blockposition.getX() + this.world.random.nextFloat());
 diff --git a/src/main/java/net/minecraft/server/NetworkManager.java b/src/main/java/net/minecraft/server/NetworkManager.java
-index d583cced6..2eddb68d7 100644
+index d583cced66..2eddb68d7b 100644
 --- a/src/main/java/net/minecraft/server/NetworkManager.java
 +++ b/src/main/java/net/minecraft/server/NetworkManager.java
 @@ -0,0 +0,0 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
@@ -1358,7 +1358,7 @@ index d583cced6..2eddb68d7 100644
          public QueuedPacket(Packet<?> packet, GenericFutureListener<? extends Future<? super Void>>... agenericfuturelistener) {
              this.a = packet;
 diff --git a/src/main/java/net/minecraft/server/PacketDataSerializer.java b/src/main/java/net/minecraft/server/PacketDataSerializer.java
-index c1273e988..d71734df8 100644
+index c1273e988e..d71734df81 100644
 --- a/src/main/java/net/minecraft/server/PacketDataSerializer.java
 +++ b/src/main/java/net/minecraft/server/PacketDataSerializer.java
 @@ -0,0 +0,0 @@ public class PacketDataSerializer extends ByteBuf {
@@ -1370,7 +1370,7 @@ index c1273e988..d71734df8 100644
          for (int j = 1; j < 5; ++j) {
              if ((i & -1 << j * 7) == 0) {
 diff --git a/src/main/java/net/minecraft/server/PacketPlayOutMapChunk.java b/src/main/java/net/minecraft/server/PacketPlayOutMapChunk.java
-index d16669bcc..306a6b7cd 100644
+index d16669bcc3..306a6b7cd3 100644
 --- a/src/main/java/net/minecraft/server/PacketPlayOutMapChunk.java
 +++ b/src/main/java/net/minecraft/server/PacketPlayOutMapChunk.java
 @@ -0,0 +0,0 @@ import java.util.Iterator;
@@ -1463,7 +1463,7 @@ index d16669bcc..306a6b7cd 100644
                  if (flag) {
                      packetdataserializer.writeBytes(chunksection.getSkyLightArray().asBytes());
 diff --git a/src/main/java/net/minecraft/server/PlayerChunk.java b/src/main/java/net/minecraft/server/PlayerChunk.java
-index 48a008e0a..395386f29 100644
+index 48a008e0a7..395386f295 100644
 --- a/src/main/java/net/minecraft/server/PlayerChunk.java
 +++ b/src/main/java/net/minecraft/server/PlayerChunk.java
 @@ -0,0 +0,0 @@ public class PlayerChunk {
@@ -1493,7 +1493,7 @@ index 48a008e0a..395386f29 100644
                  } else {
                      this.a((Packet) (new PacketPlayOutMultiBlockChange(this.dirtyCount, this.dirtyBlocks, this.chunk)));
 diff --git a/src/main/java/net/minecraft/server/PlayerInteractManager.java b/src/main/java/net/minecraft/server/PlayerInteractManager.java
-index a49b5c81a..5ec7f5819 100644
+index a49b5c81a8..5ec7f5819f 100644
 --- a/src/main/java/net/minecraft/server/PlayerInteractManager.java
 +++ b/src/main/java/net/minecraft/server/PlayerInteractManager.java
 @@ -0,0 +0,0 @@ public class PlayerInteractManager {
@@ -1506,10 +1506,10 @@ index a49b5c81a..5ec7f5819 100644
  
      public void a(BlockPosition blockposition) {
 diff --git a/src/main/java/net/minecraft/server/RegistryBlockID.java b/src/main/java/net/minecraft/server/RegistryBlockID.java
-index 8860a0129..fa0d66d63 100644
+index 03894df54c..76f6f35bb9 100644
 --- a/src/main/java/net/minecraft/server/RegistryBlockID.java
 +++ b/src/main/java/net/minecraft/server/RegistryBlockID.java
-@@ -0,0 +0,0 @@ public class RegistryBlockID<T> implements Registry { // Paper - Fix decompile e
+@@ -0,0 +0,0 @@ public class RegistryBlockID<T> implements Registry<T> {
          return Iterators.filter(this.b.iterator(), Predicates.notNull());
      }
  
@@ -1518,7 +1518,7 @@ index 8860a0129..fa0d66d63 100644
          return this.a.size();
      }
 diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
-index 90f946e57..ea67b61b2 100644
+index 90f946e57a..ea67b61b2b 100644
 --- a/src/main/java/net/minecraft/server/World.java
 +++ b/src/main/java/net/minecraft/server/World.java
 @@ -0,0 +0,0 @@ import org.bukkit.generator.ChunkGenerator;
@@ -1555,7 +1555,7 @@ index 90f946e57..ea67b61b2 100644
  
      public void a(BlockPosition blockposition, Block block, EnumDirection enumdirection) {
 diff --git a/src/main/java/org/bukkit/craftbukkit/generator/CustomChunkGenerator.java b/src/main/java/org/bukkit/craftbukkit/generator/CustomChunkGenerator.java
-index 9942f0c75..2da6edc63 100644
+index 9942f0c750..2da6edc63e 100644
 --- a/src/main/java/org/bukkit/craftbukkit/generator/CustomChunkGenerator.java
 +++ b/src/main/java/org/bukkit/craftbukkit/generator/CustomChunkGenerator.java
 @@ -0,0 +0,0 @@ public class CustomChunkGenerator extends InternalChunkGenerator {

Spigot-Server-Patches/isChunkGenerated-API.patch

@@ -6,7 +6,7 @@ Subject: [PATCH] isChunkGenerated API
 Resolves #1329
 
 diff --git a/src/main/java/net/minecraft/server/ChunkProviderServer.java b/src/main/java/net/minecraft/server/ChunkProviderServer.java
-index 0eba3df5..ad548590 100644
+index 0eba3df571..ad5485908d 100644
 --- a/src/main/java/net/minecraft/server/ChunkProviderServer.java
 +++ b/src/main/java/net/minecraft/server/ChunkProviderServer.java
 @@ -0,0 +0,0 @@ public class ChunkProviderServer implements IChunkProvider {
@@ -23,7 +23,7 @@ index 0eba3df5..ad548590 100644
      public Chunk getLoadedChunkAt(int i, int j) {
          long k = ChunkCoordIntPair.a(i, j);
 diff --git a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
-index 567e9acb..afb141c6 100644
+index 567e9acb13..afb141c629 100644
 --- a/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
 +++ b/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
 @@ -0,0 +0,0 @@ public class CraftWorld implements World {