[3.15] gh-151496: Use process groups in test_dtrace (GH-151512) by miss-islington · Pull Request #151589 · python/cpython

Create a new process group to run bpftrace commands, so it's possible
to kill also child processes on timeout.
(cherry picked from commit a064b323f4350305e7486c7b1090cf12b19e7738)

Co-authored-by: Victor Stinner <vstinner@python.org>