Paper/Spigot-API-Patches/0131-Remove-deadlock-risk-in-firing-async-events.patch
Aikar 17b58d00d8
Unwrap Event Exceptions
This was a useless exception wrapper that ends up making
stack traces harder to read as well as the JVM cutting off
the important parts

Nothing catches this exception, so its safe to just get rid
of it and let the REAL exception bubble down
2019-02-23 12:17:41 -05:00

123 lines
5.0 KiB
Diff

From 562bc11c9c2f58733eaad70a3428fcf14e0c8cc5 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 d925423d..59c70b8a 100644
--- a/src/main/java/org/bukkit/plugin/SimplePluginManager.java
+++ b/src/main/java/org/bukkit/plugin/SimplePluginManager.java
@@ -386,7 +386,7 @@ 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 {
@@ -394,7 +394,7 @@ 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);
@@ -431,7 +431,7 @@ 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 {
@@ -491,6 +491,7 @@ 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.
@@ -500,22 +501,7 @@ 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