From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Thu, 3 Mar 2016 01:17:12 -0600
Subject: [PATCH] Ensure commands are not ran async

Plugins calling Player.chat("/foo") or Server.dispatchCommand() could
trigger the server to execute a command while on another thread.

These commands would then process EXPECTING to be on the main thread, leaving to
very hard to trace concurrency issues.

This change will synchronize the command execution back to the main thread, causing a
big slowdown in execution but throwing an exception at same time to raise awareness
that it is happening so that plugin authors can fix their code to stop executing commands async.

diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index 4fc871595a2449cb22bceb8ed279fe91166597f9..2bb324f8186c70319446af3f639191c8e99f9de5 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -1859,6 +1859,29 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Ser
         }
 
         if (!async && s.startsWith("/")) {
+            // Paper Start
+            if (!org.spigotmc.AsyncCatcher.shuttingDown && !org.bukkit.Bukkit.isPrimaryThread()) {
+                final String fCommandLine = s;
+                MinecraftServer.LOGGER.log(org.apache.logging.log4j.Level.ERROR, "Command Dispatched Async: " + fCommandLine);
+                MinecraftServer.LOGGER.log(org.apache.logging.log4j.Level.ERROR, "Please notify author of plugin causing this execution to fix this bug! see: http://bit.ly/1oSiM6C", new Throwable());
+                Waitable wait = new Waitable() {
+                    @Override
+                    protected Object evaluate() {
+                        chat(fCommandLine, false);
+                        return null;
+                    }
+                };
+                server.processQueue.add(wait);
+                try {
+                    wait.get();
+                    return;
+                } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt(); // This is proper habit for java. If we aren't handling it, pass it on!
+                } catch (Exception e) {
+                    throw new RuntimeException("Exception processing chat command", e.getCause());
+                }
+            }
+            // Paper End
             this.handleCommand(s);
         } else if (this.player.getChatVisibility() == ChatVisiblity.SYSTEM) {
             // Do nothing, this is coming from a plugin
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
index c00f2263b8cee28d32e73c1eddaeb02be9e8b68c..d645c9d3d9b3af58e9fafb03cbf74c2ee49d1fd4 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
@@ -758,6 +758,28 @@ public final class CraftServer implements Server {
         Validate.notNull(commandLine, "CommandLine cannot be null");
         org.spigotmc.AsyncCatcher.catchOp("command dispatch"); // Spigot
 
+        // Paper Start
+        if (!org.spigotmc.AsyncCatcher.shuttingDown && !Bukkit.isPrimaryThread()) {
+            final CommandSender fSender = sender;
+            final String fCommandLine = commandLine;
+            Bukkit.getLogger().log(Level.SEVERE, "Command Dispatched Async: " + commandLine);
+            Bukkit.getLogger().log(Level.SEVERE, "Please notify author of plugin causing this execution to fix this bug! see: http://bit.ly/1oSiM6C", new Throwable());
+            org.bukkit.craftbukkit.util.Waitable<Boolean> wait = new org.bukkit.craftbukkit.util.Waitable<Boolean>() {
+                @Override
+                protected Boolean evaluate() {
+                    return dispatchCommand(fSender, fCommandLine);
+                }
+            };
+            net.minecraft.server.MinecraftServer.getServer().processQueue.add(wait);
+            try {
+                return wait.get();
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt(); // This is proper habit for java. If we aren't handling it, pass it on!
+            } catch (Exception e) {
+                throw new RuntimeException("Exception processing dispatch command", e.getCause());
+            }
+        }
+        // Paper End
         if (this.commandMap.dispatch(sender, commandLine)) {
             return true;
         }
diff --git a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
index 19c44daaa407b7c1c7a7ffe56fef8c8814c6d5b2..6a073a9dc44d93eba296a0e18a9c7be8a7881725 100644
--- a/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
+++ b/src/main/java/org/bukkit/craftbukkit/util/ServerShutdownThread.java
@@ -13,6 +13,7 @@ public class ServerShutdownThread extends Thread {
     public void run() {
         try {
             org.spigotmc.AsyncCatcher.enabled = false; // Spigot
+            org.spigotmc.AsyncCatcher.shuttingDown = true; // Paper
             this.server.close();
         } finally {
             try {
diff --git a/src/main/java/org/spigotmc/AsyncCatcher.java b/src/main/java/org/spigotmc/AsyncCatcher.java
index bbf0d9d9c44fe8d7add2f978994ec129420814c7..7a23b56752f6733ee626a8b1e4c3b78591855c4e 100644
--- a/src/main/java/org/spigotmc/AsyncCatcher.java
+++ b/src/main/java/org/spigotmc/AsyncCatcher.java
@@ -6,6 +6,7 @@ public class AsyncCatcher
 {
 
     public static boolean enabled = true;
+    public static boolean shuttingDown = false; // Paper
 
     public static void catchOp(String reason)
     {
diff --git a/src/main/java/org/spigotmc/RestartCommand.java b/src/main/java/org/spigotmc/RestartCommand.java
index 882e93ad4471e3688f2fcfb1e6f16926786ee5e7..94d8ba376cd1f024b244654cac9bb62bb19e3060 100644
--- a/src/main/java/org/spigotmc/RestartCommand.java
+++ b/src/main/java/org/spigotmc/RestartCommand.java
@@ -43,6 +43,7 @@ public class RestartCommand extends Command
     private static void restart(final String restartScript)
     {
         AsyncCatcher.enabled = false; // Disable async catcher incase it interferes with us
+        org.spigotmc.AsyncCatcher.shuttingDown = true; // Paper
         try
         {
             String[] split = restartScript.split( " " );