QWaylandGLContext::makeCurrent() calls QWaylandWindow::createDecoration() but the function itself is not written to be thread safe. It has been that way since at least before 2014 (https://codereview.qt-project.org/c/qt/qtwayland/+/95947) and we haven't seen any issues with it, probably because createDecoration() is called seldomly.

However, there is the possibility that something might fail there.