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

(cherry picked from commit 67a3a8f34892a6491ba0073a3f583503b44e58e7)

1 files changed, 8 insertions, 1 deletions

diff --git a/kdesktop/lockeng.cc b/kdesktop/lockeng.cc
index 278c49fc0..e178328c3 100644
--- a/kdesktop/lockeng.cc
+++ b/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;