From dabd3e4d0f10c1edbf09632a331af369251570b1 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 cb2b0b9c..a7dd902f 100644 --- a/src/main/java/org/bukkit/plugin/SimplePluginManager.java +++ b/src/main/java/org/bukkit/plugin/SimplePluginManager.java @@ -385,7 +385,7 @@ 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 { @@ -393,7 +393,7 @@ 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); @@ -430,7 +430,7 @@ 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 { @@ -490,6 +490,7 @@ 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. @@ -499,22 +500,7 @@ 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(); diff --git a/src/test/java/org/bukkit/plugin/PluginManagerTest.java b/src/test/java/org/bukkit/plugin/PluginManagerTest.java index 6b86128e..56308c0c 100644 --- a/src/test/java/org/bukkit/plugin/PluginManagerTest.java +++ b/src/test/java/org/bukkit/plugin/PluginManagerTest.java @@ -19,7 +19,7 @@ public class PluginManagerTest { private static final PluginManager pm = TestServer.getInstance().getPluginManager(); private final MutableObject store = new MutableObject(); - +/* // Paper start - remove unneeded test @Test public void testAsyncSameThread() { final Event event = new TestEvent(true); @@ -30,14 +30,14 @@ public class PluginManagerTest { return; } throw new IllegalStateException("No exception thrown"); - } + }*/ // Paper end @Test public void testSyncSameThread() { final Event event = new TestEvent(false); pm.callEvent(event); } - +/* // Paper start - remove unneeded test @Test public void testAsyncLocked() throws InterruptedException { final Event event = new TestEvent(true); @@ -58,7 +58,7 @@ public class PluginManagerTest { secondThread.join(); assertThat(store.value, is(instanceOf(IllegalStateException.class))); assertThat(event.getEventName() + " cannot be triggered asynchronously from inside synchronized code.", is(((Throwable) store.value).getMessage())); - } + }*/ // Paper end @Test public void testAsyncUnlocked() throws InterruptedException { -- 2.20.1