Date: Thu, 3 Mar 2005 08:23:39 -0800 (PST)
From: Linus Torvalds <torvalds@osdl.org>
To: Jeff Garzik <jgarzik@pobox.com>
cc: Greg KH <greg@kroah.com>, "David S. Miller" <davem@davemloft.net>,
       akpm@osdl.org, linux-kernel@vger.kernel.org
Subject: Re: RFD: Kernel release numbering
In-Reply-To: <4226CA7E.4090905@pobox.com>
Message-ID: <Pine.LNX.4.58.0503030750420.25732@ppc970.osdl.org>
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On Thu, 3 Mar 2005, Jeff Garzik wrote:
>
> Greg KH wrote:
> > Sure they've been asking for it, but I think they really don't know what
> > it entails.  Look at all of the "non-stable" type patches in the -ac and
> > as tree.  There's a lot of stuff in there.  It's a slippery slope down
> > when trying to say, "I'm only going to accept bug fixes." 
> 
> We have all these problems precisely because _nobody_ is saying "I'm 
> only going to accept bug fixes".  We _need_ some amount of release 
> engineering.  Right now we basically have none.

I agree that this is one of the main problems.

But look at how to solve it. The _logical_ solution is to have a third
line of defense: we have the -mm trees (wild and wacky patches), and we
have my tree (hopefully not wacky any more), and it would be good to have
a third level tree (which I'm just not interested in, because that one
doesn't do any development any more) which only takes the "so totally not
wild that it's really boring" patches.

In fact, if somebody maintained that kind of tree, especially in BK, it 
would be trivial for me to just pull from it every once in a while (like 
ever _day_ if necessary). But for that to work, then that tree would have 
to be about so _obviously_ not wild patches that it's a no-brainer.

So what's the problem with this approach? It would seem to make everybody
happy: it would reduce my load, it would give people the alternate "2.6.x
base kernel plus fixes only" parallell track, and it would _not_ have the 
testability issue (because I think a lot of people would be happy to test 
that tree, and if it was always based on the last 2.6.x release, there 
would be no issues.

Anybody?

I'll tell you what the problem is: I don't think you'll find anybody to do
the parallell "only trivial patches" tree. They'll go crazy in a couple of
weeks. Why? Because it's a _damn_ hard problem. Where do you draw the
line? What's an acceptable patch? And if you get it wrong, people will
complain _very_ loudly, since by now you've "promised" them a kernel that
is better than the mainline. In other words: there's almost zero glory,
there are no interesting problems, and there will absolutely be people who 
claim that you're a dick-head and worse, probably on a weekly basis.

That said, I think in theory it's a great idea. It might even be 
technically feasible if there was some hard technical criteria for each 
patch that gets accepted, so that you don't have the burn-out problem. 

So let's loook at how we could set that up. We need:

 - a sucker who wants to do this, or a company that pays for somebody good 
   to do this (and remember: "good" here doesn't necessarily have to mean 
   technical genius, it's about taking abuse and being stable). The whole 
   setup should be such that there can never be any question about the 
   patches for _other_ reasons (to avoid the sucker becoming a target for 
   abuse), so this person really to some degree would be fairly 
   mechanical.

   Don't make it automated, though. That just gets us down the path of 
   flaming about the scripts and automation. And I'm not claiming that we 
   should aim for somebody _stupid_, I'm just claiming that it takes a
   certain kind of person to do something that is not all that glamorous, 
   and that puts you in the spot.

   We don't ever want to have that spark of "wouldn't this be cool" in
   this project. 

 - some very _technical_ and objective rules on patches. And they should 
   limit the patches severely, so that people can never blame the sucker 
   who does the job. For example, I would suggest that "size" be one hard 
   technical rule. If the patch is more than 100 lines (with context) in
   size, it's not trivial any more. Really. Two big screenfuls (or four, 
   for people who still use the ISO-ANSI standard 80x24 vt100)

   Also, I'd suggest that a _hard_ rule (ie nobody can override it) would 
   also be that the problem causes an oops, a hang, or a real security
   problem that somebody can come up with an exploit for (ie no "there
   could be a two-instruction race" crap. Only "there is a race, and
   here's how you exploit it"). The exploit wouldn't need to be full code 
   that gets root, but an explanation of it, at least.

 - a vetting process. You'd have ten people, and five of them would have 
   to sign off on the patch, and even a single veto would shoot it down. 

   Again, this is really to protect the sucker, and make it possible to
   work: I don't think this can work with a creative person (everybody
   else calls me "flaky", and I much prefer that "creative" word, it sounds
   so much better), which I personally believe means that we don't _want_
   people like Alan, Andrea, Andrew etc etc that have historically maintained
   their own trees that sometimes have tried to do something like this.

 - Finally: this tree never has any history past the "last release". When
   a new kernel comes, the tree is frozen, and never to be touched again.

   If somebody _else_ wants to base things off this special "sucker tree", 
   and make a fourth level tree that is based on the _previous_ stable 
   tree, that's fine, but that's a separate process. He would be totally 
   free to do so, but the rule is that this particular maintenance program 
   _never_ gets stuck on an old kernel, like the vendor trees always are. 

   This is not a long-range tree, it would _purely_ be about one thing and
   one thing only: the last stable kernel. The people involved (sucker and 
   vetters all) would never have to remember two different trees, or care 
   about problems that aren't in the top-of-tree. Keep ti simple, and keep 
   the rules clear.

Does this mean that some patches would never go into this tree? Yes. It
would mean that patches that some people might feel very _strongly_ are
good patches would never ever show up in this tree, but on the other hand,
I can see this tree being useful regardless, and I think the lack of
flexibility in this case is actually the whole _point_ of the tree. The 
lack of flexibility is the very thing that makes this be the kind of base 
that anybody else can then hang their own patches on top of. There should 
never be a situation where "I'd like that tree, but I think xxxx was done 
wrong".

Might something like this make people happier? (I wrote "happy" rather
than "happier" at first, but let's face it, people are better at whining
than they are at being happy ;)

			Linus
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