Linux Torvalds announced release of Linux Kernel 4.0 through official mailing list. This release of Kernel features Dynamic patching mechanism, that allows to update the system without rebooting.
According to Mail by Linus:
So I decided to release 4.0 as per the normal schedule, because there really weren't any known issues, and while I'll be traveling during the end of the upcoming week due to a college visit, I'm hoping that won't affect the merge window very much. We'll see.
Linux 4.0 was a pretty small release both in linux-next and in final size, although obviously "small" is all relative. It's still over 10k non-merge commits. But we've definitely had bigger releases (and judging by linux-next v4.1 is going to be one of the bigger ones).