Interrupt controller

An interrupt controller 210 comprises issue circuitry 224 to issue interrupt requests to a processing element 202 and control circuitry 220 to detect presence of a race condition in association with at least one pending interrupt request to be issued, and to set a barrier indicator when the race condition has been resolved. In response to the race condition being present, the issue circuitry is configured to select one of the at least one pending interrupt requests and issue to the processing element the selected pending interrupt request followed by a dummy request over a path that ensures that the processing element receives the selected pending interrupt request prior to receiving the dummy request. On receiving an acknowledgement indicating that the processing element has received the dummy request, the control circuitry is then configured to set the barrier indicator. The processing element may employ a plurality of operating systems 206-2, 206-4, 206-6 under control of a hypervisor 208-2, and the race condition may occur when a target operating system for the interrupt request is not the resident operating system of the processor.