A condition wait on a recursive mutex locked more than once unlocked the
native mutex only once, so the thread that should signal blocked forever
on it. Unlock the remaining levels before the wait and lock them again
after it, as FreeBSD libthr does in _mutex_cv_unlock and _mutex_cv_lock.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HeC9bA3n74TzJRYv9AgBE8
clem-gb