Messages in this thread | | | Date | Fri, 27 Mar 2009 09:02:08 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: Linux 2.6.29 |
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On Fri, 27 Mar 2009, Mike Galbraith wrote: > > > > If you're using the kernel-of-they-day, you're probably using git, and > > CONFIG_LOCALVERSION_AUTO=y should be mandatory. > > I sure hope it never becomes mandatory, I despise that thing. I don't > even do -rc tags. .nn is .nn until baked and nn.1 appears.
If you're a git user that changes kernels frequently, then enabling CONFIG_LOCALVERSION_AUTO is _really_ convenient when you learn to use it.
This is quite common for me:
gitk v$(uname -r)..
and it works exactly due to CONFIG_LOCALVERSION_AUTO (and because git is rather good at figuring out version numbers). It's a great way to say "ok, what is in my git tree that I'm not actually running right now".
Another case where CONFIG_LOCALVERSION_AUTO is very useful is when you're noticing some new broken behavior, but it took you a while to notice. You've rebooted several times since, but you know it worked last Tuesday. What do you do?
The thing to do is
grep "Linux version" /var/log/messages*
and figure out what the good version was, and then do
git bisect start git bisect good ..that-version.. git bisect bad v$(uname -r)
and off you go. This is _very_ convenient if you are working with some "random git kernel of the day" like I am (and like hopefully others are too, in order to get test coverage).
> (would be nice if baked were immediately handed to stable .nn.0 instead > of being in limbo for a bit, but I don't drive the cart, just tag along > behind [w. shovel];)
Note that the "v2.6.29[-rcX" part is totally _useless_ in many cases, because if you're working past merges, and especially if you end up doing bisection, it is very possible that the main Makefile says "2.6.28-rc2", but the code you're working on wasn't actually _merged_ until after 2.6.29.
In other words, the main Makefile version is totally useless in non-linear development, and is meaningful _only_ at specific release times. In between releases, it's essentially a random thing, since non-linear development means that versioning simply fundamentally isn't some simple monotonic numbering. And this is exactly when CONFIG_LOCALVERSION_AUTO is a huge deal.
(It's even more so if you end up looking at "next" or merging other peoples trees. If you only ever track my kernel, and you only ever fast-forward - no bisection, no nothing - then the release numbering looks "simple", and things like LOCALVERSION looks just like noise).
Linus
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