ISRsafe

ISRsafe refers to a set of practices, tools, and terminology used in embedded and real-time systems to improve the safety and reliability of interrupt service routines (ISRs). The goal is to ensure deterministic timing, prevent data corruption, and minimize the impact of interrupts on the overall system.

Key principles include keeping ISR code short and fast, performing only essential actions, returning control as quickly as possible, deferring lengthy work to deferred procedures or a real-time task, and using safe synchronization techniques. Developers emphasize avoiding dynamic memory allocation inside ISRs, limiting shared state, and using atomic operations or lock-free data structures when appropriate. When interrupts are disabled, the window is kept as short as feasible, and memory barriers are employed to preserve ordering across cores.

ISRsafe is often implemented with guidelines and verification tools, including static analysis, formal methods, and compliance with standards such as MISRA C and ISO 26262 in automotive contexts. Code examples, design patterns, and testing suites are used to validate worst-case execution time, jitter, and interrupt nesting behavior.

Applications are found in safety-critical domains such as automotive control units, aerospace avionics, medical devices, and industrial automation, where reliable interrupt handling is essential. The approach supports a mix of simple microcontrollers and more capable RTOS-based systems.

Limitations include potential increases in development time and code size, the need for rigorous testing, and the possibility that overly conservative designs degrade system performance. ISRsafe remains a guideline and not a universal standard, requiring adaptation to specific hardware, software architecture, and safety requirements.