An interrupt controller for controlling processing of interrupt requests by a plurality of processing units. The processing units have at least two modes: an active mode and an inactive mode. The interrupt controller comprises a controller input, an interrupt router coupled to the controller input and a monitoring unit. The monitoring unit outputs a routing change signal to the interrupt router if it determines that a selected processing unit, to which, in response to a received interrupt request, an execution of an interrupt service routine was initially routed, is in inactive mode while a preselected one is in the active mode. The interrupt router reroutes the execution of the interrupt service routine to the preselected processing unit.