In order to improve maintainability and portability of (embedded) operating systems other solutions to the inter-rupt synchronization problem should be pursued. This pa-per presents a solution to the synchronization problem of interrupt-driven, non-sequential code by making assump-tions about the invocation patterns of an interrupt service routine (ISR). In addition, the model proceeds from a spe-cific structure, or modularization, of an interrupt-handling subsystem that dismembers an ISR into two closely re-lated parts. The flow of control from one part to the other one of an ISR is regulated by a synchronized queue. This queue then represents the single point at which interrupt safeness has to be ensured. It is the point where the pro-posed interrupt-transparent (non-blocking/optimistic) syn-chronization of shared data structures takes place.