Scheduler implementation

The architecture of the system depends on the way the scheduler is implemented. Tasks can be running in a cooperative model until they voluntarily decide to yield the CPU to the next task, or the OS can decide to trigger an interrupt to swap the running task behind the scenes, applying a specific policy to decide the interval in between task switches and the priority for the selection of the next task. In both cases, the context switch happens within one of the supervisor calls available, set to decide which tasks to schedule next, and to perform the context switch. In this section, the full context switch procedure through PendSV will be added to our example, and then a few of the possible scheduling policies will be analyzed and implemented.

Supervisor calls

The core component of the scheduler consists of the exception handler associated with the system interrupt events, such as PendSV and SVCall. On Cortex-M, a PendSV exception can be triggered at...