How can you avoid common issues when debugging interrupts?

This depends on architecture of the HW you are dealing with . If it’s single core then it’s a bit easier . If you are dealing with multi core architecture then you might be using more advanced interrupt controllers . For example Arm GIC has more feature where it’s per cpu and priority , fast & slow interrupts . One of the first steps you want to do is disable all interrupts for that cpu. Then you can step through the interrupt handler . Also make sure watch dog timer interrupts disabled as well .

Para evitar problemas comuns ao depurar interrup??es, é importante seguir algumas práticas recomendadas. Uma das práticas recomendadas é usar pontos de interrup??o no código-fonte para pausar a execu??o do depurador em pontos específicos do código. Além disso, é importante garantir que os pontos de interrup??o sejam definidos corretamente e que n?o haja conflitos com outros pontos de interrup??o. Outra prática recomendada é usar ferramentas de observabilidade e monitoramento para identificar problemas de interrup??o, degrada??o do servi?o, bugs e atividades n?o autorizadas. Por fim, é importante garantir que as ferramentas de depura??o sejam compatíveis com as regulamenta??es de privacidade e seguran?a de dados.

Priority & Nesting: - Issue: Conflicts arise when multiple interrupts with different priorities occur simultaneously, causing unexpected behavior. - Tip: Ensure proper prioritization of interrupts and manage nested interrupt handling appropriately. Shared Resource: - Issue: Race conditions or data corruption can occur when multiple interrupts access shared resources simultaneously. - Tip: Use synchronization mechanisms (mutexes, etc) to protect critical sections of code accessed by interrupts. Latency and Timing: - Issue: Delays to respond to interrupts or meeting timing constraints can impact system responsiveness or cause missed deadlines. - Tip: Optimize interrupt handling routines to minimize latency.

Good always to make sure the OS works well with a minimal or basic configuration to do so i do boot in safe mode cause it helps boot up the OS to find and remove troublesome glitches that are causing the OS to crash.

A mutex does NOT protect a shared resource which is shared between interrupt and task context. One possibility is to disable the interrupt while the task accesses the shared resource.

When working on real-time systems, debugging using breakpoints is often not viable, due to the impact this often has on the overall system timings. In my experience, instrumenting the code by toggling GPIO (or similar) lines connected to a Logic Analyser when certain code conditions are met can be an invaluable method of debugging interrupt-related code without significantly impacting system timings.

Debugger and Emulators: - Employ hardware debugging tools, JTAG/SWD debuggers/in-circuit emulators/ debug probes. Profiling and Monitoring: - Profiling tools or system monitors that capture interrupt behavior, timing, and resource utilization. RTOS-aware Debugging: -For (RTOS), use debugging tools that are specifically designed to understand and visualize RTOS-specific features. Logic Analyzers or Oscilloscopes: - Use logic analyzers or oscilloscopes to observe interrupt signals, their timing, and interactions with other signals on h/w pins. Hardware Tracing and Event Counters: - Microcontrollers provide hardware-based tracing mechanisms or event counters that record interrupt occurrences, execution time etc.

Probably many times it's not a good idea to set breakpoints and inspect variables in interrupt context since you totally destroy the timing and will miss further interrupts by increasing the time spent in interrupt context. Tracing tools might be better.

Hardware Testing: - Integrate the interrupt handlers with the actual hardware and perform tests by triggering interrupts using appropriate hardware input. Functional & Performance Testing: - Measure and analyze interrupt latency to ensure it meets system requirements. - Identify and optimize any delays or bottlenecks affecting interrupt response times. Edge Cases and Error Scenarios: - Error Handling: Introduce error conditions or faulty interrupt scenarios. RTOS-Specific Testing: - Test interrupt handlers in conjunction with RTOS tasks to ensure synchronization, task switching, and priority management.

Synchronization: - Use synchronization primitives like mutexes, semaphores - Use Atomic operations or lock-free data structures which are uninterruptible Critical Section Management: - Keep Critical Sections Short - Avoid Nested Locks to prevent deadlocks. - Always ensure that locks are acquired and released in threads or interrupt contexts. Queue & Event: - Use Queue passing between threads using queues. - Use event-driven architectures to minimize shared resource access and promote use of nonblocking methods.

Standard locks, such as semaphores don't work between interrupt and task context. Atomic operations might work. But take care that the "lock" is only taken for a very short amount of time. Spin locks might work as well. Another strategy might be deferred interrupt handling where you move code from interrupt context to non interrupt context.

Priority inversion typically occurs between tasks and not between interrupt and task context. A mutex with priority inversion protection might help.

It's scenario where the HP(higher-priority) task being blocked by the LP(lower-priority) task accessing a shared resource. Use Priority Inheritance: - the priority of the LP task briefly inherits the priority of the HP task until the resource is released. Minimize Resource Holding Time: - Encourage tasks to hold shared resources for the shortest time possible. Smart Use of Synchronization Mechanisms - Implement mutexes or semaphores to control access to shared resources to prevent unnecessary delays for HP tasks.

... or you can defer code from interrupt to task context. This will shorten the interrupt service routine and allow you to use blocking functions in task context, which are not allowed in interrupt context.

- Keep interrupt service routines (ISRs) as short with essential tasks. - Disable interrupts for critical sections to prevent interruptions - Decide priorities to interrupts based on their criticality - Pre-calculate or Pre-process Data to reduce computational overhead within ISRs. - Use mutexes, semaphores, or atomic operations to manage access to shared resources efficiently - Reduce Shared Resource Access: Minimize the amount of shared data accessed in ISRs

Three key concepts I try to front of mind when working in this area: * Minimise the time spent in the initial ISR code: service the interrupt, pass the data on (if relevant), and be ready for the next interrupt as soon as possible. * Consider the system behaviour as a whole, and not just the driver / module you are developing. * Remember that the interrupt behaviour of many hardware peripherals can be configured: don't just accept the default configuration if it doesn't suit your system.

- The worst-case timing needs to be considered in designing the application. - Nonblocking function is called inside ISR - Share resource is very critical - Use Efficient IPC to communicate between processes. - Avoid pooling. - Task & and thread priority must decided before creating it. - Must do Performance Profiling