Comment 16 for bug 1386473

I'm reasonably sure the problematic change is this one: http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-utopic.git;a=commit;h=8ee41919feea10de065e3102de4cbf0c57fc60ea

It was fixed upstream: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/arch/x86/kernel/smpboot.c?id=728e5653e6fdb2a0892e94a600aef8c9a036c7eb . This needs to be cherry-picked into Utopic.

I'm building a Utopic kernel with that patch applied now, and will test it shortly.