When running JRuby on an AIX machine and calling IO.select to check sockets for available data, the return value incorrectly includes sockets that have nothing available to read. For example,
ready = IO.select([sock], [sock], nil, 0)
when sock has no data available for reading, will result in [sock] for ready[0] on AIX while other systems will have an empty array for ready[0].

A simple test can be seen here: https://gist.github.com/3949918

This test script fails on AIX running either java 6 or java 7, but succeeds when running java 5.
The behavior is the same on AIX 5.3 and AIX 6.1 (sorry, I don't have an AIX 7.1 or other PPC system to test with).
The test succeeds as expected on other systems, including a linux (intel, not ppc) box running with IBM's jvm.