Applying Static WCET Analysis to Automotive Communication Software

The number of embedded computers used in modern cars have increased dramatically during the last years, as they provide increased functionality to a reduced cost compared to previous technologies. These computers are often connected by one or more communication networks and the data traffic sent over the networks often has hard real-time requirements. To provide overall system timing guarantees, upper timing bounds need to be derived both for the data traffic and the embedded computer programs that controls the communication.In this article, we present a case study where static Worst-Case Execution Time (WCET) analysis was used to find upper time bounds for time-critical code in products from Volcano Communications Technologies AB (VCT). The VCT company provides tools for development of real-time communication solutions for embedded network systems, mainly used within the car industry. VCT's tool suite includes support for Controller Area Network (CAN), Local Interconnect Network (LIN), FlexRay and MOST network traffic. The primary purpose of the study was not to test the accuracy of the obtained WCET estimates, but rather to investigate the practical difficulties that arise when applying current WCET analysis methods to these particular kind of systems. A central question was if today's static WCET analysis tools can be used in the automotive software development process. In particular, we were interested in how labor-intensive the analysis becomes, measured by the number of manual annotations necessary to perform the analysis. As a result, we provide some qualitative observations on desirable research results for making static WCET analysis applicable in typical automotive software development.