Maybe there should be a way to tell Trio "hey I don't want the worker threads anymore, please kill them!", especially in light of the new deprecation warning (ATM the way to do that is to do time.sleep(10)). Maybe Trio should explicitly support this use case and set up a callback for before os.fork() s.t. all the threads get killed.

That's not what this PR does!

Counterpoint: what if a thread is currently doing work (no guarantees even outside of a trio.run because abandon_on_cancel).

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00000%. Comparing base (8a7674c) to head (0855d7c).

@@               Coverage Diff               @@
##                 main        #3200   +/-   ##
===============================================
  Coverage   100.00000%   100.00000%           
===============================================
  Files             124          124           
  Lines           18792        18818   +26     
  Branches         1268         1270    +2     
===============================================
+ Hits            18792        18818   +26     

coverage fail appears to be coveragepy/coveragepy#310
seems to be workarounds in there, though this is minor enough we could ofc just # pragma: no cover

The coverage stuff definitely isn't worth it for the test coverage, but doing this stop/save thing also covers the callback from register_at_fork. Otherwise that doesn't get any coverage.