Fix desktop lock failure due to race condition within signal handler between qt and xcb

(cherry picked from commit 67a3a8f348)

kdesktop/lock/lockprocess.cc

@@ -664,6 +664,7 @@ void LockProcess::startSecureDialog()
 	}
 	trinity_desktop_lock_in_sec_dlg = false;
 	if (ret == 0) {
+		trinity_desktop_lock_closing_windows = 1;
 		kapp->quit();
 	}
 	if (ret == 1) {
@@ -687,6 +688,7 @@ void LockProcess::startSecureDialog()
 		mBusy = false;
 	}
 	if (ret == 2) {
+		trinity_desktop_lock_closing_windows = 1;
 		if (system("ksysguard &") == -1) {
                     // Error handler to shut up gcc warnings
                 }

kdesktop/lock/main.cc

@@ -266,7 +266,7 @@ int main( int argc, char **argv )
 
         bool rt;
         bool sig = false;
-        if( (!child && (args->isSet( "forcelock" )) || (signalled_forcelock == TRUE))) {
+        if( (((!child) && (args->isSet( "forcelock" ))) || (signalled_forcelock == TRUE))) {
             rt = process.lock();
             sig = true;
         }

kdesktop/lockeng.cc

@@ -34,7 +34,7 @@ SaverEngine* m_masterSaverEngine = NULL;
 static void sigusr1_handler(int)
 {
     if (m_masterSaverEngine) {
-        m_masterSaverEngine->lockProcessWaiting();
+        m_masterSaverEngine->slotLockProcessWaiting();
     }
 }
 
@@ -445,6 +445,13 @@ void SaverEngine::lockProcessExited()
     }
 }
 
+void SaverEngine::slotLockProcessWaiting()
+{
+    // lockProcessWaiting cannot be called directly from a signal handler, as it will hang in certain obscure circumstances
+    // Instead we use a single-shot timer to immediately call lockProcessWaiting once control has returned to the Qt main loop
+    TQTimer::singleShot(0, this, SLOT(lockProcessWaiting()));
+}
+
 void SaverEngine::lockProcessWaiting()
 {
     kdDebug(1204) << "SaverEngine: lock exited" << endl;

kdesktop/lockeng.h

@@ -79,11 +79,12 @@ public:
     virtual void saverLockReady();
 
 public slots:
-    void lockProcessWaiting();
+    void slotLockProcessWaiting();
 
 protected slots:
     void idleTimeout();
     void lockProcessExited();
+    void lockProcessWaiting();
 
 private slots:
     void handleSecureDialog();