Torture test for atomics and userland locking?

[Tim Kientzle]

Can anyone suggest a good test suite for stressing atomic
primitives and/or userland locking?

There were some questions on freebsd-arm about verifying
that our atomics are correct; a few people have looked at the
code and everything looks good so far, but it would be
reassuring to have some test suite that could provide additional
confidence.

Tim