Since 20151231 -next has been failing to boot on a wide range of ARM platforms in the kernelci.org boot tests[1]. Doing bisections with Arndale and BeagleBone Black identifies 904769ac82ebf (mm/page_alloc.c: calculate zone_start_pfn at zone_spanned_pages_in_node()) from the akpm tree as the first broken commit[2,3]. An example bootlog from the failure is:
http://storage.kernelci.org/next/next-20151231/arm-multi_v7_defconfig/lab-ca...
which shows no output on the console once we start the kernel, a brief sampling of failing boards suggests this is the normal failure mode. x86 and arm64 targets seem fine (juno shows up as failing but the boot log seems fine so it's probably a false positive, Mustang was failing already) and there are a small number of ARM platforms that boot. I've not yet had any time to investigate further than that (including trying a revert of that commit), sorry.
[1] http://kernelci.org/boot/all/job/next/kernel/next-20151231/ [2] https://ci.linaro.org/view/people/job/tbaker-boot-bisect-bot/135/console [3] https://ci.linaro.org/view/people/job/tbaker-boot-bisect-bot/136/console