Vehicle Control Device Priority Reversal Suppression
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Solution Overview
Problem
In vehicle control devices, priority reversal occurs when low safety software calls high safety software, causing subsequent processes with higher priority levels to be delayed or not completed within predetermined execution intervals due to the same priority level being assigned to interruption processes, regardless of safety levels.
Innovation Solution
A vehicle control device with an execution waiting job list that inserts requests from low safety software to call high safety software at a position corresponding to the execution priority level of the low safety software, ensuring that these requests are executed in the correct order to prevent priority reversal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the same priority level is assigned to all interruption processes regardless of safety levels, then the interruption controller can manage processes in generated order, but priority reversal occurs causing subsequent processes with higher priority levels to be delayed
Solution Approach 1:
The patent applies local quality by assigning different priority levels to interruption processes based on their safety levels. High safety software interruption processes are assigned higher priority levels than low safety software interruption processes, allowing each interruption process to have differentiated quality characteristics appropriate to its safety requirements, thereby preventing priority reversal while maintaining manageable operation
2Reliability
If low safety software is prohibited from rewriting the authority configuration register, then high safety software is protected from unexpected operations, but the operational mode switching requires predetermined interruption processes that may cause priority reversal
Solution Approach 1:
The patent changes the priority level parameter of interruption processes based on the safety level of the software generating the interruption. By dynamically adjusting the priority level parameter according to safety requirements, the system maintains protection of high safety software while ensuring that high safety interruption processes are executed before low safety ones, preventing execution delays
3Ease of manufacture
If multiple pieces of software with different safety levels are implemented on the same microcontroller, then implementation cost is optimized, but memory protection and priority management complexity increases
Solution Approach 1:
The patent uses parameter changes by assigning different priority level parameters to interruption processes based on their originating software's safety level. This simple parameter-based differentiation allows the system to manage multiple software with different safety levels on the same microcontroller without requiring complex memory protection or priority management mechanisms, thereby optimizing implementation cost while controlling complexity
Data Source
AI summary
Executing control software with an appropriate execution priority in accordance with a safety standard in a vehicle control device that executes a plurality of control software having different safety standards suppresses priority degree reversal. A vehicle control device is provided with an execution waiting job list retaining a list of jobs waiting for execution by a processor. A request for calling higher safety software from lower safety software is inserted at a position in the execution waiting job list in accordance with the execution priority of the lower safety software.