A high-level datarace occurs when an execution interleaves instructions corresponding to user-annotated critical accesses to shared memory structures. Such races are good indicators of atomicity violations. We propose a technique for detecting all high-level dataraces in a system library like the kernel API of a real-time operating system (RTOS) that relies on flag-based scheduling and synchronization. Our methodology is based on model-checking, but relies on a meta-argument to bound the number of task processes needed to orchestrate a race. We describe our approach in the context of FreeRTOS, a popular RTOS in the embedded domain.