For kernel updates you must to reboot. But I read something about live patching:
http://www.zdnet.com/article/no-reboot-patching-comes-to-linux-4-0/ http://www.eweek.com/enterprise-apps/linux-4.0-goes-live-with-live-kernel-patching.html http://news.softpedia.com/news/Linus-Torvalds-Releases-Linux-Kernel-4-0-RC1-Final-Version-Will-Bring-Live-Patching-473921.shtml
