Boot up fail with linux-next source code tag next-20141226

Hi, I am trying to build and boot linux-next kernel tree.  My original kernel with Ubuntu 12.04 LTS was 3.5.0-23-generic.  I checked out code with tag next-20141226. I generated a ".config" file with "make localmodconfig". I installed modules and kernel.On restart PC do not boot up.  I then checked out tag v3.16-rc3 and booted. It worked pretty good and booted properly. I had few question from this exercise: 1) Why my PC didn't boot up with linux-next kernel?2) Do I need to apply any specific patches to boot mainline linux-next kernel on my Ubuntu 12.04 PC?3) How do people test mainline kernel-next? Do they apply their OS specific patch on linux-next tree or test linux-next on some specific OS? Thanks,Sunil.