It’s good news for system admin’s, they don’t have to reboot the system after applying an important patch to the kernel. Thanx to Ksplice, an Open source extension of linux kernel which allows admins to apply patches to running kernel.
What ksplice does is, it only takes an unified diff of a patch, and applies it to running kernel. It does this work in the memory. It determines the change to be done on source code by analyzing the Executable and Linking Format(ELF) object layer and not on C source code. Ksplice freezes all the processors in the system and make sure it is the only process running at the time of patch. After applying a patch, it resumes the processors and points all the functions to the newly updated data and structures in the memory.
To use Ksplice you don’t even need a special compiled kernel. You can try Ksplice on ubuntu and fedora by visiting this link