How to unbreak LTTng

Maintaining an in-tree module is *way* less work than maintaining an out-of-tree one. Heck, most of the time you just have to say "Ack" on the patches that the person changing some kernel infrastructure _writes for you_ to keep your module working. Whereas out-of-tree you end up with elaborate compatibility scripts, that you have to keep updated without any outside help, unless you're happy for your module to either only build on the latest kernel, or be tied to 2.6.32 forever 'cos that's what was ubiquitous when you started the project.

If it's tight enough with the kernel to be a module (rather than a userspace executable, using the APIs that are actually designed to be stable), then it belongs in the upstream tree; and if it's not good enough quality to be upstream (even in staging or behind a 'default n' kconfig) then it doesn't belong anywhere.