Real-time embedded systems typically include concurrent tasks of different priorities with time-dependent operations accessing common resources. In this context, unsynchronized parallel executions may lead to hazard situations caused by e.g., race conditions. To be able to detect such faulty system behaviors before implementation, we introduce a unified model of resource constrained, scheduled real-time system descriptions, in Alur's and Henzinger's rigorous framework of timed reactive modules. We take a??component-based design perspective and construct thereal-time system model, by refinement, as a composition ofreal-time periodic preemptible tasks with encoded functionality, and a fixed-priority scheduler, all modeled as timed modules. For the model, we express the notions of race condition and redundant locking, formally, as invariance properties that can be verifiedby model-checking.