What are the best practices for handling concurrency in embedded systems?

1 Concurrency models

Different ways to implement concurrency in embedded systems depend on the hardware architecture, the operating system, and the application requirements. Multithreading is a common model which allows multiple threads of execution to run within a single process, sharing memory and resources. They can be created, managed, and synchronized by the operating system or by a user-level library. Multiprocessing is another model that enables multiple processes to run on a single or multiple cores, each with its own memory and resources. Processes can communicate and synchronize through inter-process communication (IPC) mechanisms such as message queues, pipes, or shared memory. Lastly, the event-driven model relies on a single thread of execution that responds to events or interrupts generated by external sources like sensors, timers, or user inputs. Events are handled by callback functions or state machines that execute in a non-blocking manner.

2 Tools and techniques

In order to handle concurrency in embedded systems, you need to use the right tools and techniques for designing, developing, debugging, and testing your concurrent code. Real-time operating systems (RTOS) provide features and services such as task scheduling, interrupt handling, memory management, and IPC. Concurrency libraries offer abstractions and utilities for creating and manipulating concurrent entities like threads, tasks, futures, promises, or coroutines. Debugging and testing tools are also essential for finding and fixing concurrency-related errors and bugs. These tools can include simulators, emulators, debuggers, profilers, analyzers, or code checkers. Utilizing these tools can simplify the implementation and management of concurrency while ensuring the timing and reliability of your system. Furthermore, they can help you write portable, scalable, and maintainable concurrent code while leveraging the hardware capabilities of your system.

3 Coding standards and guidelines

To handle concurrency in embedded systems, you need to follow coding standards and guidelines that can help you write clear, consistent, and robust concurrent code. It is important to use descriptive and meaningful names for your concurrent entities such as threads, tasks, or events. Additionally, global variables or shared resources should be avoided as they can cause data inconsistency or interference among concurrent entities. Mutexes, semaphores, or atomic operations should be used to protect critical sections or shared resources. Error and exception handling mechanisms should also be implemented to deal with unexpected situations or failures in your concurrent code. Assertions, logging, or reporting functions should be used to monitor and debug your concurrent code. Furthermore, the principle of least privilege should be followed and give your concurrent entities the minimum access and authority they need to perform their functions. Priority levels, affinity masks, or resource limits can be used to control the allocation and execution of your concurrent entities. Finally, it is important to document your concurrent code and explain the design decisions, assumptions, and dependencies of your concurrency model using comments, diagrams, or annotations.