While trying to run the "compiler.compiler" benchmark from SPECjvm2008,
I noticed we seem to have a problem with concurrent use of filesystem
operations - which often hang (waiting on a vn_lock()) or cause
assertion failures.

This trivial test - which does stat() calls in 10 concurrent threads -
reproduces this bug, and usually (but not always) crashes on one of
several assertion failures, or hangs.