stat() cannot (on platforms I am familiar with) be performed in a selectish/nonblocking way. That call can block forever. Local filesystem access in general is still not async-capable in very important ways.
Yes, filesystem calls are going to block -- but putting that into a limited threadpool shouldn't deadlock your system -- you can't do a blocking read on a file, waiting for it to be filled by another thread (unless/until you start playing with FUSE, I guess.
