Integration of enhanced slot-shifting in uc/os-II

The growing complexity of embedded applications poses new challenges in the application development phase. The time-critical nature of the embedded applications leads to the use of an Real-Time Operating System (RTOS). Typically in a RTOS, applications are divided into a small number of concurrent functional units called tasks. The execution of tasks is accomplished through the scheduler of a RTOS. The job of the scheduler is to pick a task for execution using a scheduling mechanism. The existing scheduling mechanisms handles tasks with only a specific set of constraints such as period and deadline.
However, applications may have a set of more complex constraints such as precedence relations between tasks and non-uniform arrival patterns of tasks. Although time-triggered schedulers can solve all these constraints off-line and scheduling decisions are also made off-line, the disadvantage of this approach is that it requires a complete knowledge of tasks and their constraints. Event-triggered schedulers partially require knowledge of tasks and their constraints, but these can handle dynamically arriving tasks with run-time mechanisms and the scheduling decisions are made online. The combination of time-triggered and event-triggered scheduler is suitable for dealing with tasks with complex constraints. Complex task constraints can be resolved during the off-line preparation phase. During run-time, those resources that are unused by the off-line guaranteed tasks can be used for the execution of dynamically arriving tasks.