Recent Kernels failing to boot?

[John Whitmore]

I'm not even sure that this is the correct home for this question but sure
it's worth a punt. I'm running OpenSUSE on a netbook and use it to compile and
install the latest kernel from Linus's git repo. This has always been a simple
operation pulling the latest, updating the config file, make and install.

A few versions ago I hit a snag in that once installed the new kernel would
show up in the grub2 menu but once selected for boot the machine would just go
to a blank screen and hang. I'd have to do a hard reset. I can't be specific
on which version this started happening on as the problem is intermittent. It
seems to be a race condition sometimes a kernel will boot and sometimes it
won't.

I thought I could investigate this issue but I can't find any debug info for
this problem at all. grub2 is happy as it's handed control over to the kernel
but there's no evidence of any kernel activity in the logs at all for the
requested boot.

So the reason for this post is to ask if anybody could suggest how to debug
this issue. I think it came in about 3.14 but like I say it's intermittent.