A lightweight scheduler to run tasks concurrently as well as special callbacks that must be run in mutual exclusion with the tasks (and each other).

Creates a new task / idle callback scheduler

Schedule a task to be run as soon as no idle callback is running, or as soon as the next idle callback has been run if it was scheduled by force_idle.

Runs a callback as soon as no task is running. Does not prevent new tasks from being scheduled, the calling code should ensure that some idle time will eventually come. Calling this function from inside the callback will result in a dead lock.

Runs a callback as soon as possible. Lets all current tasks finish, but postpones all new tasks until the end of the callback. Calling this function from inside the callback will result in a dead lock.