Fix long-standing intermittent bug whereby an application using dbus-1-tqt would randomly hang after many hours of continuous operation

2 files changed, 27 insertions, 2 deletions

diff --git a/tqdbusconnection_p.h b/tqdbusconnection_p.h
index cf64c2c..97537f0 100644
--- a/tqdbusconnection_p.h
+++ b/tqdbusconnection_p.h
@@ -144,6 +144,11 @@ public:
     };
     typedef TQMap<DBusPendingCall*, TQT_DBusPendingCall*> PendingCallMap;
     PendingCallMap pendingCalls;
+
+    typedef TQValueList<TQT_DBusMessage> PendingMessagesForEmit;
+    PendingMessagesForEmit pendingMessages;
+
+    bool inDispatch;
 };
 
 #endif
diff --git a/tqdbusintegrator.cpp b/tqdbusintegrator.cpp
index 373e4a0..55af1e0 100644
--- a/tqdbusintegrator.cpp
+++ b/tqdbusintegrator.cpp
@@ -273,7 +273,7 @@ int TQT_DBusConnectionPrivate::registerMessageMetaType()
 
 TQT_DBusConnectionPrivate::TQT_DBusConnectionPrivate(TQObject *parent)
     : TQObject(parent), ref(1), mode(InvalidMode), connection(0), server(0),
-      dispatcher(0)
+      dispatcher(0), inDispatch(false)
 {
     static const int msgType = registerMessageMetaType();
     Q_UNUSED(msgType);
@@ -452,6 +452,13 @@ void TQT_DBusConnectionPrivate::scheduleDispatch()
 
 void TQT_DBusConnectionPrivate::dispatch()
 {
+    // dbus_connection_dispatch will hang if called recursively
+    if (inDispatch) {
+        printf("[dbus-1-tqt] WARNING: Attempt to call dispatch() recursively was silently ignored to prevent lockup!\n\r"); fflush(stdout);
+        return;
+    }
+    inDispatch = true;
+
     if (mode == ClientMode)
     {
         if (dbus_connection_dispatch(connection) != DBUS_DISPATCH_DATA_REMAINS)
@@ -460,6 +467,15 @@ void TQT_DBusConnectionPrivate::dispatch()
             dispatcher->stop();
         }
     }
+
+    inDispatch = false;
+
+    for (TQT_DBusConnectionPrivate::PendingMessagesForEmit::iterator pmfe = pendingMessages.begin(); pmfe != pendingMessages.end(); ++pmfe) {
+        TQT_DBusMessage msg = *pmfe;
+        pendingMessages.remove(pmfe);
+        pmfe = pendingMessages.begin();
+        dbusSignal(msg);
+    }
 }
 
 bool TQT_DBusConnectionPrivate::handleObjectCall(DBusMessage *message)
@@ -481,7 +497,11 @@ bool TQT_DBusConnectionPrivate::handleSignal(DBusMessage *message)
     // FIXME-QT4
     //return handleSignal(TQString(), msg) | handleSignal(msg.path(), msg);
 
-    dbusSignal(msg);
+    // If dbusSignal(msg) were called here, it could easily cause a lockup as it would enter the TQt3 event loop,
+    // which could result in arbitrary methods being called while still inside dbus_connection_dispatch.
+    // Instead, I enqueue the messages here for TQt3 event loop transmission after dbus_connection_dispatch is finished.
+    pendingMessages.append(msg);
+
     return true;
 }