Re: [Ksummit-discuss] bug-introducing patches

[Matthew Wilcox <willy6545@gmail.com>]

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I think your sample size omits some people. I run Debian Testing on my
laptop. That gets something akin to a Linus release pretty soon after he
releases it, and while it gets some amount of -stable patches, it
progresses to the next release fairly rapidly.

Added Ben to the cc for more updates.

I think Fedora does something similar.

On Tue, May 8, 2018, 16:29 Sasha Levin via Ksummit-discuss, <
ksummit-discuss@lists.linuxfoundation.org> wrote:

> On Mon, May 07, 2018 at 11:48:20PM -0400, Theodore Y. Ts'o wrote:
> >On Tue, May 08, 2018 at 02:34:41AM +0000, Sasha Levin via Ksummit-discuss
> wrote:
> >>
> >> Tony, I'm curious, how many users are you aware of who actually run
> >> Linus's tree? All the users I've encountered so far on Azure seem to be
> >> running something based on -stable.
> >
> >The people who run Linus's tree and test -rc kernels tend to be kernel
> >developers and individual users who want to run bleeding edge kernels
> >and who generally are technically clueful.  If you were talking about
> >SLR cameras, you'd call them the "prosumers" segment of the market.
> >
> >It tends to be more on desktops and laptops, so it doesn't surprise me
> >that you don't often see them in a hosting environment where you have
> >to pay $$$.  (And where you do see them in a hosting environment, it's
> >probably for things like gce-xfstests.)
> >
> >> I think that a question we should be asking ourselves is whether we
> >> should be basing our decisions here on the assumption that (pretty much)
> >> no one runs Linus's tree anymore?
> >
> >These people *do* exist, because as a maintainer, I get bug reports
> >from them.  (And sometimes as a user, I send bug reports when running
> >-rc kernels to other maintainers, such as the i915 drivers and the
> >Intel Wireless driver folks.)
> >
> >Such reports are incredibly valuable and precious to me, since it
> >allows me to find problems that weren't picked up in my own testing.
> >(In the case of Intel Wireless, a while back the IWL team didn't have
> >Aruba Enterprise Access Points in their test hardware library, so I
> >found a regression after the merge window because I was running -rcX
> >on my laptop, and wireless access to googleguest network broke.  If I
> >hadn't been running -rcX, they probably wouldn't have discovered this
> >problem until after that particular kernel had been released.)
> >
> >So keeping those users happy is a good thing; since they tend to be
> >very technically clueful, they can do bisections for you, and they are
> >able to give a detailed and useful bug report.  If they report that a
> >regression that was introduced in -rc2 is fixed by a particular patch,
> >I want to push it into -rc3 immediately, and not let it stall in
> >linux-next.  If the reason why is because you don't trust my patch
> >because it "only" got tested by the technically advanced user
> >reporting the regression, then don't take patches from -rc3 into your
> >stable branch right away!  Let it bake in Linus's tree anfor a week or
> >two, instead of demanding that patches stick around in Linux-next
> >before flowing into Linus's tree.
> >
> >Because I will guarantee you this --- there are more real users
> >running Linus's tree than linux-next.  This is because Linus's tree
> >tends to be far more stable than linux-next, since after -rc2
> >linux-next starts getting the first set of experiments for what will
> >be going into the next merge window.  So while I am willing to run
> >something based on -rc2 or later on my laptop, there is no way in heck
> >I would be willing to put linux-next on my laptop.  That's just way
> >too exciting for me....
> >
> >Would I pull down linux-next, and fire up a VM running gce-xfstests?
> >Sure.  But that's not a real-life use case; that's just running canned
> >test cases.  And more often than not, linux-next will be broken while
> >Linus's -rcX tree is just fine; which is why I do most of my ext4
> >testing using patches based on top of -rcX, not based on top of
> >linux-next.
>
> This is interesting. We have a group of power users who are testing out
> -rc releases, who are usually happy to test out a fast moving target and
> provide helpful reports back. We also have a group who run a -stable
> kernel (-stable build/distro/android/etc) who want to avoid having to
> report bugs to us.
>
> What we don't have is a group of people who use Linus's actual releases
> (not the -rc stuff, but the actual point releases). Power users will
> move on to the next kernel, and -stable folks won't touch that release
> until there's a corresponding -stable.
>
> Even rawhide, like Josh mentioned, will just fill back with the merge
> window commits after the release of an older kernel.
>
> So the problem I'm seeing is that since a merge window is open only once
> every 2-3 months people will sometimes try to push poorly tested code
> just to make that merge window. Additionally, as later -rc releases
> start showing up people will again merge poorly tested fixes just to
> make it in time for that release.
>
> For both cases, people will push poorly tested code in the kernel just
> because they want to make it in time for a kernel release that no one
> will actually use.
>
> What if, instead, Linus doesn't actually ever release a point release?
> We can make the merge window open more often, and since there's no
> actual release, people won't rush to push fixes in later -rc cycles.
>
> We take away the incentive to push poorly tested code. Maintainers still
> free to commit anything they'd like, but there's no reason to commit
> code they're not confident of just to make it to a random release no one
> will use.
>
> Merge window will happen more often, so there's no real reason to rush
> things in a particular window, and since -stable releases every week
> there's no rush to push a fix in since the next release is just a week
> away.
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