For details how this works refer to the documentation in the patch. The follow-up patches will switch to calling processXcbEvents() on every event loop iteration. With the existing code that would mean frequent locking of shared data (event queue). Acquiring a lock is fast, but lock contention isn't. To avoid potential problems, reimplement xcb event processing to be lock-free. Besides theoretical performance benefits, this definitally improves code readability in qxcbconnection.cpp. Thanks to Mikhail Svetkin for questioning the design of the existing code. Done-with: Mikhail Svetkin <mikhail.svetkin@qt.io> Change-Id: I935f2b6ca802580f5c80205aef7b2f9afc172d26 Reviewed-by: Mikhail Svetkin <mikhail.svetkin@qt.io> Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>