suspendable/resumable/prioritizable task dispatcher

Hi,

Unfortunately I don't have the vocabulary needed to ask this question, 
but hopefully I'll learn it here.

Does Boost have something that will help me with this problem:

I have a list of CPU-bound tasks I need to perform.  I'll list two of 
them here:

    a) compute first zillion digits of pi (low priority)
    b) add two plus two (high priority)

I co_spawn (a).  Later, while (a) is running, I co_spawn (b).  (a) will 
be suspended at a "co_suspension_point" so that (b) can take over.  Of 
course when (b) completes, (a) will resume.

For bonus points, it will support multiple threads (probably easy) and a 
task's priority can change over time (probably hard).

Thank you!

Chris

PS: I was recently blown away by the coroutine capability of ASIO: 
Talking Async Ep1: Why C++20 is the Awesomest Language for Network 
Programming https://www.youtube.com/watch?v=icgnqFM-aY4