Task Services

Task Lifecycle

The kernel automatically starts the background task during system initialization.

Once the background task is started it executes forever. If the task attempts to terminate by returning from main(), the kernel puts the task into a permanant idling state since the background task must always be available to execute.

Task Scheduling

The nanokernel’s scheduler executes the background task only when there is no fiber or ISR that needs to execute, since fiber and ISR execution takes precedence.

The kernel automatically takes care of saving the background task’s CPU register values when it performs a context switch to a fiber or an ISR. It restores these values when the background task later resumes execution.

Defining the Background Task

The application must supply a function of the following form:

void main(void)
{
    /* background task processing */
    ...
    /* (optional) enter permanent idling state */
    return;
}

This function is used as the background task’s entry point function. If a nanokernel application does not need to perform any task-level processing main() can simply do an immediate return.

The MAIN_STACK_SIZE configuration option specifies the size, in bytes, of the memory region used for the background task’s stack and for other execution context information.