Some environments are currently not working well with Preempt-RT. Here is an overview of known limitations and workarounds.

The Raspberry PI 3 is currently not part of the mainline kernel and requires an out of tree patch for its Support. This support also includes an USB driver which may lock up the RT System. Possible workarounds:

• Disable the USB driver (dwc_otg)
• Disable the FIQ support in the driver with the following module option / kernel command line:

dwc_otg.fiq_enable=0
dwc_otg.fiq_fsm_enable=0

• There is an article on OSADL about this problem including a patch how to use the FIQ support and not lock up the system.