Sharing display lists

I’m working on an Onyx2 with multiple IR3 graphics boards. I have a shared-memory application which can render in parallel to multiple pipes when the pipes are on the same X server (:0.0 and :0.1). I get a GLXBadContext error if I try to share display lists when the pipes are configured on multiple X servers (:0.0 and :1.0). According to the man page for glXCreateContext, this error should only occur when the given context is not valid. Since I am using direct context in a shared-memory app it seems like this should be ok. Any ideas as to why this fails?