From 92f253cc74a436388b15369e370bd96c3e19713a Mon Sep 17 00:00:00 2001
From: Florian Schmaus <flo@geekplace.eu>
Date: Wed, 28 Sep 2022 13:52:58 +0200
Subject: [PATCH] [core] Replace AbstractXMPPConnection.inOrderListeners

Using AsyncButOrdered for the receive listeners means that a listener
may not have been yet run once
invokeStanzaCollectorsAndNotifyRecvListeners() returnes. This can lead
to deadlocks as reported by Boris Grozev [1].

Fixes SMACK-927.

1: https://discourse.igniterealtime.org/t/thread-stuck-in-multiuserchat-enter-forever/92090
---
 .../org/jivesoftware/smack/AbstractXMPPConnection.java   | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java b/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java
index 5a3ae04ac..0e710ee03 100644
--- a/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java
+++ b/smack-core/src/main/java/org/jivesoftware/smack/AbstractXMPPConnection.java
@@ -33,6 +33,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.Semaphore;
 import java.util.concurrent.ThreadFactory;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -348,8 +349,6 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
 
     protected static final AsyncButOrdered<AbstractXMPPConnection> ASYNC_BUT_ORDERED = new AsyncButOrdered<>();
 
-    protected final AsyncButOrdered<StanzaListener> inOrderListeners = new AsyncButOrdered<>();
-
     /**
      * The used host to establish the connection to
      */
@@ -1613,8 +1612,9 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
 
         listenersToNotify.clear();
         extractMatchingListeners(packet, recvListeners, listenersToNotify);
+        final Semaphore listenerSemaphore = new Semaphore(1 - listenersToNotify.size());
         for (StanzaListener stanzaListener : listenersToNotify) {
-            inOrderListeners.performAsyncButOrdered(stanzaListener, () -> {
+            asyncGoLimited(() -> {
                 try {
                     stanzaListener.processStanza(packet);
                 }
@@ -1623,9 +1623,12 @@ public abstract class AbstractXMPPConnection implements XMPPConnection {
                 }
                 catch (Exception e) {
                     LOGGER.log(Level.SEVERE, "Exception in packet listener", e);
+                } finally {
+                    listenerSemaphore.release();
                 }
             });
         }
+        listenerSemaphore.acquireUninterruptibly();
 
         // Notify the receive listeners interested in the packet
         listenersToNotify.clear();