[mistwang]

The lsws log shows that, ruby just simply closed the connection, not sending anything back.

The ruby process you straced is the parent ruby process which does nothing but accept a connection and fork a child ruby process to handle the request. I really interested is what happened in the child process. I think it crashed, probably.

Is the rails log from litespeed or from other setup?

Are you setup your Rails app with the easy configuration? or step by step manually?
You are using rewrite rules to dispatch the request, have you tried using 404 handler?

Let me know your exact rails setup, I will try to duplicate it in our lab.