MessageUtil.doDelayed/postTick is thread-unsafe

[Johni0702]

The MessageUtil.doDelayed system relies on a single backing queue:

BuildCraft/common/buildcraft/lib/misc/MessageUtil.java

Lines 45 to 59 in 8bac6a7

	private static final DelayedList<Runnable> DELAYED_TASKS = DelayedList.createConcurrent();
	public static void doDelayed(Runnable task) {
	doDelayed(1, task);
	}
	public static void doDelayed(int delay, Runnable task) {
	DELAYED_TASKS.add(delay, task);
	}
	public static void postTick() {
	for (Runnable runnable : DELAYED_TASKS.advance()) {
	runnable.run();
	}
	}

It is however used on the client (ref) and the server (ref), leading to runnables being shuffled between both threads at random and all the fun stuff that follows from that (e.g. Johni0702/BetterPortals#458).

Example stack trace of illegal access (with modified version of BP)

[16:09:43] [Client thread/ERROR] [betterportals/view]: Exception caught in net handler of view of EntityPlayerMP['Johni0702'/207, l='#458', x=563.30, y=4.31, z=-423.70]: 
java.util.ConcurrentModificationException: channel is locked for iteration
	at de.johni0702.minecraft.view.impl.server.SafeEmbeddedChannel.handleOutboundMessage(ServerWorldsManagerImpl.kt:41) ~[SafeEmbeddedChannel.class:?]
	at io.netty.channel.embedded.EmbeddedChannel.doWrite(EmbeddedChannel.java:674) ~[EmbeddedChannel.class:4.1.9.Final]
	at io.netty.channel.AbstractChannel$AbstractUnsafe.flush0(AbstractChannel.java:856) ~[AbstractChannel$AbstractUnsafe.class:4.1.9.Final]
	at io.netty.channel.AbstractChannel$AbstractUnsafe.flush(AbstractChannel.java:823) ~[AbstractChannel$AbstractUnsafe.class:4.1.9.Final]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.flush(DefaultChannelPipeline.java:1296) ~[DefaultChannelPipeline$HeadContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.ChannelOutboundHandlerAdapter.flush(ChannelOutboundHandlerAdapter.java:115) ~[ChannelOutboundHandlerAdapter.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.ChannelOutboundHandlerAdapter.flush(ChannelOutboundHandlerAdapter.java:115) ~[ChannelOutboundHandlerAdapter.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush(AbstractChannelHandlerContext.java:768) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.flush(AbstractChannelHandlerContext.java:749) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.flush(NetworkDispatcher.java:555) ~[NetworkDispatcher.class:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeFlush0(AbstractChannelHandlerContext.java:776) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:802) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:814) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:794) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:831) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:1032) ~[DefaultChannelPipeline.class:4.1.9.Final]
	at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:296) ~[AbstractChannel.class:4.1.9.Final]
	at net.minecraft.network.NetworkManager.func_150732_b(NetworkManager.java:225) ~[gw.class:?]
	at net.minecraft.network.NetworkManager.func_179290_a(NetworkManager.java:168) ~[gw.class:?]
	at net.minecraftforge.fml.common.network.handshake.NetworkDispatcher.sendProxy(NetworkDispatcher.java:462) ~[NetworkDispatcher.class:?]
	at net.minecraftforge.fml.common.network.FMLOutboundHandler.write(FMLOutboundHandler.java:389) ~[FMLOutboundHandler.class:?]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:730) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:816) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:723) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.handler.codec.MessageToMessageEncoder.write(MessageToMessageEncoder.java:111) ~[MessageToMessageEncoder.class:4.1.9.Final]
	at io.netty.handler.codec.MessageToMessageCodec.write(MessageToMessageCodec.java:116) ~[MessageToMessageCodec.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:738) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:801) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:814) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:794) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:831) ~[AbstractChannelHandlerContext.class:4.1.9.Final]
	at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:1032) ~[DefaultChannelPipeline.class:4.1.9.Final]
	at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:296) ~[AbstractChannel.class:4.1.9.Final]
	at net.minecraftforge.fml.common.network.simpleimpl.SimpleNetworkWrapper.sendTo(SimpleNetworkWrapper.java:250) ~[SimpleNetworkWrapper.class:?]
	at buildcraft.lib.net.MessageManager.sendTo(MessageManager.java:221) ~[MessageManager.class:?]
	at buildcraft.core.BCCoreEventDist.lambda$onEntityJoinWorld$0(BCCoreEventDist.java:37) ~[BCCoreEventDist.class:?]
	at buildcraft.lib.misc.MessageUtil.postTick(MessageUtil.java:57) [MessageUtil.class:?]
	at buildcraft.lib.BCLibEventDist.clientTick(BCLibEventDist.java:141) [BCLibEventDist.class:?]
	at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_27_BCLibEventDist_clientTick_ClientTickEvent.invoke(.dynamic) [?:?]
	at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90) [ASMEventHandler.class:?]
	at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182) [EventBus.class:?]
	at net.minecraftforge.fml.common.FMLCommonHandler.onPostClientTick(FMLCommonHandler.java:349) [FMLCommonHandler.class:?]
	at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1911) [bib.class:?]
	at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1098) [bib.class:?]
	at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:398) [bib.class:?]
	at net.minecraft.client.main.Main.main(SourceFile:123) [Main.class:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_242]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_242]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_242]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_242]
	at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
	at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_242]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_242]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_242]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_242]
	at org.multimc.onesix.OneSixLauncher.launchWithMainClass(OneSixLauncher.java:196) [NewLaunch.jar:?]
	at org.multimc.onesix.OneSixLauncher.launch(OneSixLauncher.java:231) [NewLaunch.jar:?]
	at org.multimc.EntryPoint.listen(EntryPoint.java:143) [NewLaunch.jar:?]
	at org.multimc.EntryPoint.main(EntryPoint.java:34) [NewLaunch.jar:?]

[AlexIIL]

Ok, this should be fixed in 7.99.24.5 - please let me know if that's not the case.