> > It's also possible that readdir() is not reentrant with lstat()
> This doesn't make much sense to me.

Me either.  I think what I was actually seeing was multiple calls to readdir() still occurring even after placing a mutex on os.listdir due to my wrapping of os.listdir in a timeout via a subthread, and mutexing the timeout-wrapped version.  I will test this more carefully tomorrow.

I will also look into creating some C code to demonstrate the bug.