Number of threads in haskell program

[chessai .]

Hi devs,

Recently I became interested in obtaining the rough number of (non-GC)
threads that are alive in a Haskell program. Intuitively this seemed
like something that the RTS would expose in some way - but I couldn't
find any such exposition in base. I then thought that I could simply
total the size of each run_queue_hd in each capability, but the
machinery for doing that doesn't seem to be exposed. Any thoughts?

Thanks