Typically Nut/OS is at its most useful where there are several concurrent tasks that need to be undertaken at the same time. To support this requirement, Nut/OS offers some kind of light processes called threads. In this context a thread is a sequence of executing software that can be considered to be logically independent from other software that is running on the same CPU.
All threads are executing in the same address space using the same hardware resources, which significantly reduces task switching overhead. Therefore it is important to stop them from causing each other problems. This is particularly an issue where two or more threads need to share a resources like memory locations or peripheral devices.
The system works on the principle that the most urgent thread always runs. One exception to this is if a CPU interrupt arrives and the interrupt has not been disabled. Each thread has a priority which is used to determine how urgent it is. This priority ranges from 0 to 255, with the lowest value indicating the most urgent.
Nut/OS implements cooperative multithreading. That means, that threads are not bound to a fixed timeslice. Unless they are waiting for specific event or explicitely yielding the CPU, they can rely on not being stopped unexpectedly. However, they may be interrupted by hardware interrupt signals. In opposite to pre-emptive multithreading, coorperative multithreading simplifies resource sharing and results in faster and smaller code.
Modules | |
| Thread States | |
| Thread operating states. | |
Data Structures | |
| struct | _NUTTHREADINFO |
| Thread information structure. More... | |
| struct | _NUTTHREADINFO |
| Thread information structure. More... | |
Typedefs | |
| typedef _NUTTHREADINFO | NUTTHREADINFO |
| typedef struct _NUTTHREADINFO NUTTHREADINFO |
Thread information structure type.
1.5.1