Damn, your reply and the other four pointing out that they're Ruby VMs reflects very poorly on the intelligence of HN commenters. Did you guys even RTFA? I know these are Ruby VMs, but the article is about the C code that's used within them. That's the only place where "volatile" has any meaning at all. Maybe "volatile" really is unknown among Ruby programmers, but among the people who implement interpreters for Ruby or any other language I can assure you it's pretty common knowledge.
I confess, I just don't know how to deal with such epic stupidity more gracefully than this. Sheesh.
YARV = Yet Another Ruby VM = Ruby 1.9
REE = Ruby Enterprise Edition = Ruby 1.8 with a modified garbage collection system to make it friendly to vforking.
These are all versions of ruby written in C.