Reliable Handling of Real-Time Scheduling Attributes on Multiprocessor Platforms in Ada 2012

The real-time attributes of a concurrent task define the parameters that will determine when the task can be allocated the required resources. Typical examples are the task’s priority, the deadline, and the CPU (or CPUs) on which it must be executed. Since the 2012 revision, Ada is prepared for handling all these attributes. But the handling is per-attribute: it is not possible to change several attributes at a time, in a single call. Instead, they have to be changed one by one, which poses scheduling issues especially in multiprocessor platforms. This paper proposes and discusses approaches for implementing atomic changes of multiple scheduling attributes, thus mitigating or eliminating those issues.