The design of embedded systems is facing the explosion of new functionalities requiring increased computation capacities and, thus, the introduction of multi-core processors. Moreover, some functionalities may impose precedence constraints between the programs implementing them. In this paper, we consider partitioned scheduling of tasks with precedence constraints defined by multiple Directed Acyclic Graphs (DAGs). The variability of execution and communication times is taken into account by describing them with probability distributions. Our probabilistic response time analysis is validated on random generated task sets and on a PX4 drone autopilot.