# Scheduling the Exchange of Context Information for Time-Triggered Adaptive Systems
## 2 Related Work  
### Adaptation in Time-Triggered Systems  
Adaptation in safety- and mixed-criticality systems is motivated by the need for energy efficiency, safety, and responsiveness to changing environmental conditions. Resource allocation in time-triggered systems is computed at design time, which significantly benefits the safety arguments of dependable systems. However, static resource allocation limits the flexibility of adaptation. Hence, the following works are efforts to provide adaptation in time-triggered systems. A network-wide reconfiguration strategy for time-triggered networks is introduced in [15]. The work proposed local, elastic, global, and degraded reconfiguration strategies. In the local reconfiguration, the network routing information and routing scheduling table information resident in the switches are unchanged. Task migration due to a failed core is carried out for the same end system or another one on the same cluster. The elastic reconfiguration is designed for low-priority traffic, where periods of low-priority traffic are increased to decrease the total load. The global reconfiguration involves remappingapplications, redistributing routes, and generating a new scheduling table for the system. Degraded reconfiguration ensures that only the most critical applications and their communication tasks are retained. The work developed an Integer Linear Programming (ILP)-based strategy for global reconfiguration. Furthermore, it developed a heuristic algorithm for mapping and routing to reduce reconfiguration time. Adaptation in safety and mixed-criticality systems is driven by energy efficiency, safety, and responses to environmental changes. While time-triggered systems benefit from design-time resource allocation for safety, this static approach limits flexibility. Many efforts focus on enabling adaptation, particularly by utilizing slack events, which arise from conservative Worst-Case Execution Time (WCET) estimates. Slack can enhance Quality-of-Service (QoS) in safety-critical systems or allow best-effort tasks in mixed-criticality systems. [PERSON] and [PERSON] in [16] propose an interference-sensitive adaptation approach capable of fine-grained synchronization. The work focused on resolving concurrency issues caused by the parallel execution of monitor updates in the system. Runtime adaptation is achieved through controllers that monitor tasks on each core. Each task is padded with a ready phase and an update phase to enable adaptation. The ready phase signifies that a task will be executed when all scheduling dependencies are met. The update phase describes the completion of a task, followed by a notification to all other cores by the controller. However, context propagation between cores is neither time-triggered nor included in the scheduling problem. Conversely, we provide a solution with timing guarantees for exchanging context between cores by scheduling the exchange of context information. Furthermore, beyond proffering a platform to adapt to slack, our proposed work extends adaptation to other events, such as failure scenarios and changing environmental conditions. Furthermore, based on exploiting slack for adaptation in time-triggered systems, the work in [17] presented a dynamic approach of adapting to interference-sensitive WCET during runtime. Their approach exploits the actual execution time of tasks in all system cores in a way that allows concurrent tasks to sustain more interference while preserving timing. The partial order of tasks is relaxed depending on the progress of each task. Moreover, the runtime variability caused by shorter task execution compared to an offline computed interference-sensitive WCET schedule is exploited for adaptation. Adaptation for fault recovery in time-triggered systems is tackled in [18]. The work presented a time-triggered extension layer for mixed-criticality network-on-chip (MCNoC), where multiple schedules are associated with specific failure events.