Did you uninstall 15.4 or did you also install 15.3?

@eskimo any idea how long it takes to review these kind of PRs?

This is a stress test. Normally there aren't that many threads running. It looks like we can optimize it and get rid of those waits on isTestInterfaceDown Thanks for the recommendations! Is this the best implementation of popen https://opensource.apple.com/source/Libc/Libc-167/gen.subproj/popen.c.auto.html ?