Usually, when a software release moves to a new single digit release, it's a big deal. When Linus Torvalds decided to shift the Linux kernel from 3.2x it was just to make developers happy.
As Torvalds, Linux's founder, said on his Google+ account: "So, I made noises some time ago about how I don't want another 2.6.39 where the numbers are big enough that you can't really distinguish them. We're slowly getting up there again, with 3.20 being imminent, and I'm once more close to running out of fingers and toes."
So Torvalds set up a survey where the choices were: "I like big versions and I cannot lie." and "v.4.0, 'cause I get confused easily." This "scientific" survey showed 56 percent of the respondents wanted version, so Torvalds decided to give it to them.
First though, over 6,000 people voted on a test poll , which Torvalds asked to be ignored, where the choices were "I like online pools" and "Hurr durr I'ma sheep". The winner was sheep with 64 percent of the vote.
As Torvalds remarked on the 4.0 git notification:
After extensive statistical analysis of my G+ polling, I've come to the inescapable conclusion that internet polls are bad.
But "Hurr durr I'ma sheep" trounced "I like online polls" by a 62-to-38% margin, in a poll that people weren't even supposed to participate in. Who can argue with solid numbers like that? 5,796 votes from people who can't even follow the most basic directions?
In contrast, "v4.0" beat out "v3.20" by a slimmer margin of 56-to-44%, but with a total of 29,110 votes right now. Now, arguably, that vote spread is only about 3,200 votes, which is less than the almost six thousand votes that the "please ignore" poll got, so it could be considered noise.
But hey, I asked, so I'll honor the votes.
So, with a lot of silliness, Linux 4.0-rc1 is now ready for testing.
Torvalds is aware that some people don't like this because of the idea that a "'major number should go with a major new feature or breaking of compatibility,' which just shows how little people know. We don't break compatibility, and we haven't done feature-based releases since basically forever."
On the other hand, Torvalds added that "the strongest argument for some people advocating 4.0 seems to have been a wish to see 4.1.15 - because 'that was the version of Linux Skynet used for the T-800 Terminator.' So on the whole, I wouldn't read too much into the number."
It's not news that techies love dumb jokes and science-fiction, which is what the move to Linux 4.0 really shows. As for the real changes in this new release, there aren't many.
Torvalds sums it up as "On an actual technical side, this was a *fairly* small release." The only real changes are the integration of live-patching into the Linux kernel and better memory page handling.
Still, with this new numbering scheme, Torvalds "can do releases without having to take off my socks again."