SPIGOT-5378: Fix TileEntity fixer deadlock

Chunk loading logic can make getTileEntity calls, and these can
be off of the main thread (i.e lighting). The TileEntity fixer
makes a getType call, which will block on chunk load. Thus a
deadlock can occur between a lighting thread and the server thread.

nms-patches/World.patch

@@ -23,6 +23,15 @@
  public abstract class World implements IIBlockAccess, GeneratorAccess, AutoCloseable {
  
      protected static final Logger LOGGER = LogManager.getLogger();
+@@ -23,7 +39,7 @@
+     protected final List<TileEntity> tileEntityListPending = Lists.newArrayList();
+     protected final List<TileEntity> tileEntityListUnload = Lists.newArrayList();
+     private final long b = 16777215L;
+-    private final Thread serverThread;
++    final Thread serverThread; // CraftBukkit - package private
+     private int u;
+     protected int i = (new Random()).nextInt();
+     protected final int j = 1013904223;
 @@ -41,7 +57,51 @@
      protected boolean tickingTileEntities;
      private final WorldBorder worldBorder;

nms-patches/WorldServer.patch

@@ -50,7 +50,7 @@
          this.nextTickListBlock = new TickListServer<>(this, (block) -> {
              return block == null || block.getBlockData().isAir();
          }, IRegistry.BLOCK::getKey, IRegistry.BLOCK::get, this::b);
-@@ -85,9 +112,40 @@
+@@ -85,9 +112,44 @@
              this.getWorldData().setGameType(minecraftserver.getGamemode());
          }
  
@@ -63,6 +63,10 @@
 +    @Override
 +    public TileEntity getTileEntity(BlockPosition pos) {
 +        TileEntity result = super.getTileEntity(pos);
++        if (Thread.currentThread() != this.serverThread) {
++            // SPIGOT-5378: avoid deadlock, this can be called in loading logic (i.e lighting) but getType() will block on chunk load
++            return result;
++        }
 +        Block type = getType(pos).getBlock();
 +
 +        if (result != null && type != Blocks.AIR) {
@@ -92,7 +96,7 @@
      public void doTick(BooleanSupplier booleansupplier) {
          GameProfilerFiller gameprofilerfiller = this.getMethodProfiler();
  
-@@ -162,6 +220,7 @@
+@@ -162,6 +224,7 @@
              this.rainLevel = MathHelper.a(this.rainLevel, 0.0F, 1.0F);
          }
  
@@ -100,7 +104,7 @@
          if (this.lastRainLevel != this.rainLevel) {
              this.server.getPlayerList().a((Packet) (new PacketPlayOutGameStateChange(7, this.rainLevel)), this.worldProvider.getDimensionManager());
          }
-@@ -180,13 +239,34 @@
+@@ -180,13 +243,34 @@
              this.server.getPlayerList().sendAll(new PacketPlayOutGameStateChange(7, this.rainLevel));
              this.server.getPlayerList().sendAll(new PacketPlayOutGameStateChange(8, this.thunderLevel));
          }
@@ -136,7 +140,7 @@
          })) {
              this.C = false;
              if (this.getGameRules().getBoolean(GameRules.DO_DAYLIGHT_CYCLE)) {
-@@ -225,7 +305,7 @@
+@@ -225,7 +309,7 @@
          this.ae();
          this.ticking = false;
          gameprofilerfiller.exitEnter("entities");
@@ -145,7 +149,7 @@
  
          if (flag3) {
              this.resetEmptyTime();
-@@ -239,6 +319,11 @@
+@@ -239,6 +323,11 @@
  
              for (i = 0; i < this.globalEntityList.size(); ++i) {
                  entity = (Entity) this.globalEntityList.get(i);
@@ -157,7 +161,7 @@
                  this.a((entity1) -> {
                      ++entity1.ticksLived;
                      entity1.tick();
-@@ -257,6 +342,7 @@
+@@ -257,6 +346,7 @@
                  Entity entity1 = (Entity) entry.getValue();
                  Entity entity2 = entity1.getVehicle();
  
@@ -165,7 +169,7 @@
                  if (!this.server.getSpawnAnimals() && (entity1 instanceof EntityAnimal || entity1 instanceof EntityWaterAnimal)) {
                      entity1.die();
                  }
-@@ -264,6 +350,7 @@
+@@ -264,6 +354,7 @@
                  if (!this.server.getSpawnNPCs() && entity1 instanceof NPC) {
                      entity1.die();
                  }
@@ -173,7 +177,7 @@
  
                  if (entity2 != null) {
                      if (!entity2.dead && entity2.w(entity1)) {
-@@ -324,10 +411,10 @@
+@@ -324,10 +415,10 @@
                      entityhorseskeleton.r(true);
                      entityhorseskeleton.setAgeRaw(0);
                      entityhorseskeleton.setPosition((double) blockposition.getX(), (double) blockposition.getY(), (double) blockposition.getZ());
@@ -186,7 +190,7 @@
              }
          }
  
-@@ -338,11 +425,11 @@
+@@ -338,11 +429,11 @@
              BiomeBase biomebase = this.getBiome(blockposition);
  
              if (biomebase.a((IWorldReader) this, blockposition1)) {
@@ -200,7 +204,7 @@
              }
  
              if (flag && this.getBiome(blockposition1).b() == BiomeBase.Precipitation.RAIN) {
-@@ -389,7 +476,7 @@
+@@ -389,7 +480,7 @@
      protected BlockPosition a(BlockPosition blockposition) {
          BlockPosition blockposition1 = this.getHighestBlockYAt(HeightMap.Type.MOTION_BLOCKING, blockposition);
          AxisAlignedBB axisalignedbb = (new AxisAlignedBB(blockposition1, new BlockPosition(blockposition1.getX(), this.getBuildHeight(), blockposition1.getZ()))).g(3.0D);
@@ -209,7 +213,7 @@
              return entityliving != null && entityliving.isAlive() && this.f(entityliving.getChunkCoordinates());
          });
  
-@@ -418,7 +505,7 @@
+@@ -418,7 +509,7 @@
              while (iterator.hasNext()) {
                  EntityPlayer entityplayer = (EntityPlayer) iterator.next();
  
@@ -218,7 +222,7 @@
                      ++i;
                  } else if (entityplayer.isSleeping()) {
                      ++j;
-@@ -436,10 +523,22 @@
+@@ -436,10 +527,22 @@
      }
  
      private void clearWeather() {
@@ -243,7 +247,7 @@
      }
  
      public void resetEmptyTime() {
-@@ -477,6 +576,7 @@
+@@ -477,6 +580,7 @@
                      return IRegistry.ENTITY_TYPE.getKey(entity.getEntityType()).toString();
                  });
                  entity.tick();
@@ -251,7 +255,7 @@
                  this.getMethodProfiler().exit();
              }
  
-@@ -562,6 +662,22 @@
+@@ -562,6 +666,22 @@
              BlockPosition blockposition = worldchunkmanager.a(0, 0, 256, list, random);
              ChunkCoordIntPair chunkcoordintpair = blockposition == null ? new ChunkCoordIntPair(0, 0) : new ChunkCoordIntPair(blockposition);
  
@@ -274,7 +278,7 @@
              if (blockposition == null) {
                  WorldServer.LOGGER.warn("Unable to find spawn biome");
              }
-@@ -637,6 +753,7 @@
+@@ -637,6 +757,7 @@
          ChunkProviderServer chunkproviderserver = this.getChunkProvider();
  
          if (!flag1) {
@@ -282,7 +286,7 @@
              if (iprogressupdate != null) {
                  iprogressupdate.a(new ChatMessage("menu.savingLevel", new Object[0]));
              }
-@@ -648,6 +765,16 @@
+@@ -648,6 +769,16 @@
  
              chunkproviderserver.save(flag);
          }
@@ -299,7 +303,7 @@
      }
  
      protected void k_() throws ExceptionWorldConflict {
-@@ -719,7 +846,8 @@
+@@ -719,7 +850,8 @@
              if (entity instanceof EntityInsentient) {
                  EntityInsentient entityinsentient = (EntityInsentient) entity;
  
@@ -309,7 +313,7 @@
                      continue;
                  }
              }
-@@ -736,11 +864,24 @@
+@@ -736,11 +868,24 @@
  
      @Override
      public boolean addEntity(Entity entity) {
@@ -336,7 +340,7 @@
      }
  
      public void addEntityTeleport(Entity entity) {
-@@ -790,13 +931,18 @@
+@@ -790,13 +935,18 @@
          this.registerEntity(entityplayer);
      }
  
@@ -357,7 +361,7 @@
              IChunkAccess ichunkaccess = this.getChunkAt(MathHelper.floor(entity.locX / 16.0D), MathHelper.floor(entity.locZ / 16.0D), ChunkStatus.FULL, entity.attachedToPlayer);
  
              if (!(ichunkaccess instanceof Chunk)) {
-@@ -824,7 +970,7 @@
+@@ -824,7 +974,7 @@
          if (entity1 == null) {
              return false;
          } else {
@@ -366,7 +370,7 @@
              return true;
          }
      }
-@@ -875,10 +1021,17 @@
+@@ -875,10 +1025,17 @@
          }
  
          this.getScoreboard().a(entity);
@@ -384,7 +388,7 @@
      }
  
      private void registerEntity(Entity entity) {
-@@ -899,9 +1052,16 @@
+@@ -899,9 +1056,16 @@
  
              this.entitiesByUUID.put(entity.getUniqueID(), entity);
              this.getChunkProvider().addEntity(entity);
@@ -401,7 +405,7 @@
          }
  
      }
-@@ -932,6 +1092,18 @@
+@@ -932,6 +1096,18 @@
      }
  
      public void strikeLightning(EntityLightning entitylightning) {
@@ -420,7 +424,7 @@
          this.globalEntityList.add(entitylightning);
          this.server.getPlayerList().sendPacketNearby((EntityHuman) null, entitylightning.locX, entitylightning.locY, entitylightning.locZ, 512.0D, this.worldProvider.getDimensionManager(), new PacketPlayOutSpawnEntityWeather(entitylightning));
      }
-@@ -940,6 +1112,12 @@
+@@ -940,6 +1116,12 @@
      public void a(int i, BlockPosition blockposition, int j) {
          Iterator iterator = this.server.getPlayerList().getPlayers().iterator();
  
@@ -433,7 +437,7 @@
          while (iterator.hasNext()) {
              EntityPlayer entityplayer = (EntityPlayer) iterator.next();
  
-@@ -948,6 +1126,12 @@
+@@ -948,6 +1130,12 @@
                  double d1 = (double) blockposition.getY() - entityplayer.locY;
                  double d2 = (double) blockposition.getZ() - entityplayer.locZ;
  
@@ -446,7 +450,7 @@
                  if (d0 * d0 + d1 * d1 + d2 * d2 < 1024.0D) {
                      entityplayer.playerConnection.sendPacket(new PacketPlayOutBlockBreakAnimation(i, blockposition, j));
                  }
-@@ -1008,6 +1192,14 @@
+@@ -1008,6 +1196,14 @@
  
      @Override
      public Explosion createExplosion(@Nullable Entity entity, DamageSource damagesource, double d0, double d1, double d2, float f, boolean flag, Explosion.Effect explosion_effect) {
@@ -461,7 +465,7 @@
          Explosion explosion = new Explosion(this, entity, d0, d1, d2, f, flag, explosion_effect);
  
          if (damagesource != null) {
-@@ -1016,6 +1208,8 @@
+@@ -1016,6 +1212,8 @@
  
          explosion.a();
          explosion.a(false);
@@ -470,7 +474,7 @@
          if (explosion_effect == Explosion.Effect.NONE) {
              explosion.clearBlocks();
          }
-@@ -1080,13 +1274,20 @@
+@@ -1080,13 +1278,20 @@
      }
  
      public <T extends ParticleParam> int a(T t0, double d0, double d1, double d2, int i, double d3, double d4, double d5, double d6) {
@@ -493,7 +497,7 @@
                  ++j;
              }
          }
-@@ -1169,7 +1370,13 @@
+@@ -1169,7 +1374,13 @@
      @Override
      public WorldMap a(String s) {
          return (WorldMap) this.getMinecraftServer().getWorldServer(DimensionManager.OVERWORLD).getWorldPersistentData().b(() -> {