Re: [Ksummit-2013-discuss] When to push bug fixes to mainline

[Rafael J. Wysocki]

On Friday, July 12, 2013 06:32:11 PM Greg Kroah-Hartman wrote:
> On Sat, Jul 13, 2013 at 02:24:07AM +0200, Rafael J. Wysocki wrote:
> > On Thursday, July 11, 2013 08:34:30 PM Greg Kroah-Hartman wrote:
> > > On Thu, Jul 11, 2013 at 10:57:46PM -0400, John W. Linville wrote:
> > > > On Thu, Jul 11, 2013 at 08:50:23PM -0400, Theodore Ts'o wrote:
> > > > 
> > > > > In any case, I've been very conservative in _not_ pushing bug fixes to
> > > > > Linus after -rc3 (unless they are fixing a regression or the bug fix
> > > > > is super-serious); I'd much rather have them cook in the ext4 tree
> > > > > where they can get a lot more testing (a full regression test run for
> > > > > ext4 takes over 24 hours), and for people trying out linux-next.
> > > > > 
> > > > > Maybe the pendulum has swung too far in the direction of holding back
> > > > > changes and trying to avoid the risk of introducing regressions;
> > > > > perhaps this would be a good topic to discuss at the Kernel Summit.
> > > > 
> > > > Yes, there does seem to be a certain ebb and flow as to how strict
> > > > the rules are about what should go into stable, what fixes are "good
> > > > enough" for a given -rc, how tight those rule are in -rc2 vs in -rc6,
> > > > etc.  If nothing else, a good repetitive flogging and a restatement of
> > > > the One True Way to handle these things might be worthwhile once again...
> > > 
> > > The rules are documented in stable_kernel_rules.txt for what I will
> > > accept.
> > > 
> > > I have been beating on maintainers for 8 years now to actually mark
> > > patches for stable, and only this past year have I finally seen people
> > > do it (we FINALLY got SCSI patches marked for stable in this merge
> > > window!!!)  So now that maintainers are finally realizing that they need
> > > to mark patches, I'll be pushing back harder on the patches that they do
> > > submit, because the distros are rightfully pushing back on me for
> > > accepting things that are outside of the stable_kernel_rules.txt
> > > guidelines.
> > 
> > I don't quite understand why they are pushing back on you rather than on
> > the maintainers who have marked the commits they have problems with for
> > -stable.  Why are you supposed to play the role of the gatekeeper here?
> > Can't maintainers be held responsible for the commits they mark for -stable in
> > the same way as they are responsible for the commits they push to Linus?
> 
> Because I'm an easy big target and people are lazy.

Well, why don't you tell them "Please talk to the maintainer directly" and if
the maintainer doesn't want to talk to them, *then* you deal with the
maintainer?

They can see in the git log who marked the commit for -stable, so contacting
that person shouldn't be too difficult.

> > Also, I don't really think that the distros have problems with fixes that are
> > simple and provably correct, even though the problems they fix don't seem to be
> > "serious enough" for -stable.  They rather have problems with subtle changes
> > whose impact is difficult to estimate by inspection and you're not going to be
> > pushing back on those anyway (exactly because their impact is difficult to
> > estimate).
> 
> I know that, you know that, but managers who see tons of kernel patches
> just get scared :)

That's an interesting angle. :-)

So you're pushing back on things that aren't "broken enough" presumably to make
those people feel better, but they will only feel better for a while until they
realize that the problems they had (generally speaking, regressions in -stable
caused by commits that shouldn't be there) are still present, even though they
don't see tons of patches any more.  I'm wondering what the point is, then?

> > > If you look on the stable@vger list, I've already rejected 3 today and
> > > asked about the huge 21 powerpc patches.  Sure, it's not a lot, when
> > > staring down 174 more to go, but it's a start...
> > 
> > And 2 of those 3 rejected were mine and for 1 of them I actually had a very
> > specific reason to mark it for -stable as I told you: It fixed a breakage
> > introduced inadvertently in 3.10 and I thought it would be good to reduce
> > the exposure of that breakage by fixing it in 3.10.1 as well as in 3.11-rc.
> 
> There was no real breakage, that is why I rejected it.

That's the root of the problem: My "real breakage" doesn't seem to be the same
as your "real breakage".  To me, if I can *see* breakage in the code, it's
broken.  And I mean breakage, not just coding style problems etc.  Code review
is our first line of breakage detection and if we catch it at that level, we
don't even ask the compiler what it thinks about that code.  We don't apply
the patch.  And if we've already applied it, which is unfortunate, there is no
reason whatsoever not to fix it.  Regardless of whether or not it is called
"stable" at this point.

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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