1. A method for switching from using a first graphics-processing unit (GPU) to using a second GPU to drive a display, comprising: using a first thread executing on a central processing unit to execute a window manager that performs operations associated with servicing user requests; receiving a request to switch from using the first GPU to using the second GPU as a signal source for driving the display; using a kernel-based second thread executing on the central processing unit to configure the second GPU in preparation for driving the display in response to the request; continuing to use the first thread to execute the window manager to service user requests while the second thread is configuring the second GPU; and switching the signal source which drives the display from the first GPU to the second GPU when configuration of the second GPU is complete.