Linus has released the 4.0 kernel right on schedule. "Feature-wise, 4.0 doesn't have all that much special. Much have been made of the new kernel patching infrastructure, but realistically, that not only wasn't the reason for the version number change, we've had much bigger changes in other versions. So this is very much a 'solid code progress' release." Beyond the (incomplete) live-patching mechanism, this release includes the removal of the remap_file_pages() system call, improved persistent memory support, the lazytime mount option, and the kernel address sanitizer.
April 13, 2015
The 4.0 Kernel Has Been Released
Read more at LWN