With background knowledge I meant all the things you have to worry about in kernel space that might not happen in userspace. Atomics, interrupt contexts, rcu, the fact that not the whole world is a VAX^Wx86.
When writing a bugfix for EFI I had to deal with early memory allocators and the transition to the full page allocator. For fun I looked up what allocators were used in the kernel. I came up with brk, e820, memblock, bootmem, xen's special brew, and the kernel's full page allocator. This list is probably incomplete. ;)