PaperMC/Bukkit-Patches/0027-Ease-ClassLoader-Deadlocks-Where-Possible.patch

From 7b22f91f252d08fdad9c53a669f51356fb34db71 Mon Sep 17 00:00:00 2001
From: md_5 <git@md-5.net>
Date: Wed, 16 Jul 2014 17:24:21 +1000
Subject: [PATCH] Ease ClassLoader Deadlocks Where Possible

When on Java 7 we can register the classloader as parallel capable to prevent deadlocks caused by certain scenarios. Due to the nature of PluginClassLoader this isn't completely safe, but we can make it safer by switching to concurrency focused collections. Either way this is far better than crashing the server.

diff --git a/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java b/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
index b081ecb..0ac8325 100644
--- a/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
+++ b/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
@@ -48,7 +48,7 @@ import org.yaml.snakeyaml.error.YAMLException;
 public final class JavaPluginLoader implements PluginLoader {
     final Server server;
     private final Pattern[] fileFilters = new Pattern[] { Pattern.compile("\\.jar$"), };
-    private final Map<String, Class<?>> classes = new HashMap<String, Class<?>>();
+    private final Map<String, Class<?>> classes = new java.util.concurrent.ConcurrentHashMap<String, Class<?>>(); // Spigot
     private final Map<String, PluginClassLoader> loaders = new LinkedHashMap<String, PluginClassLoader>();
     public static final CustomTimingsHandler pluginParentTimer = new CustomTimingsHandler("** Plugins"); // Spigot
 
diff --git a/src/main/java/org/bukkit/plugin/java/PluginClassLoader.java b/src/main/java/org/bukkit/plugin/java/PluginClassLoader.java
index 13f8633..4cffa13 100644
--- a/src/main/java/org/bukkit/plugin/java/PluginClassLoader.java
+++ b/src/main/java/org/bukkit/plugin/java/PluginClassLoader.java
@@ -17,7 +17,7 @@ import org.bukkit.plugin.PluginDescriptionFile;
  */
 final class PluginClassLoader extends URLClassLoader {
     private final JavaPluginLoader loader;
-    private final Map<String, Class<?>> classes = new HashMap<String, Class<?>>();
+    private final Map<String, Class<?>> classes = new java.util.concurrent.ConcurrentHashMap<String, Class<?>>(); // Spigot
     private final PluginDescriptionFile description;
     private final File dataFolder;
     private final File file;
@@ -25,6 +25,30 @@ final class PluginClassLoader extends URLClassLoader {
     private JavaPlugin pluginInit;
     private IllegalStateException pluginState;
 
+    // Spigot Start
+    static
+    {
+        try
+        {
+            java.lang.reflect.Method method = ClassLoader.class.getDeclaredMethod( "registerAsParallelCapable" );
+            if ( method != null )
+            {
+                boolean oldAccessible = method.isAccessible();
+                method.setAccessible( true );
+                method.invoke( null );
+                method.setAccessible( oldAccessible );
+                org.bukkit.Bukkit.getLogger().log( java.util.logging.Level.INFO, "Set PluginClassLoader as parallel capable" );
+            }
+        } catch ( NoSuchMethodException ex )
+        {
+            // Ignore
+        } catch ( Exception ex )
+        {
+            org.bukkit.Bukkit.getLogger().log( java.util.logging.Level.WARNING, "Error setting PluginClassLoader as parallel capable", ex );
+        }
+    }
+    // Spigot End
+    
     PluginClassLoader(final JavaPluginLoader loader, final ClassLoader parent, final PluginDescriptionFile description, final File dataFolder, final File file) throws InvalidPluginException, MalformedURLException {
         super(new URL[] {file.toURI().toURL()}, parent);
         Validate.notNull(loader, "Loader cannot be null");
-- 
2.1.0