Re: linus-next: improving functional testing for to-be-merged pull requests

[Sasha Levin]

On Mon, Oct 21, 2024 at 11:48:34PM -0700, Christoph Hellwig wrote:
> On Mon, Oct 21, 2024 at 09:54:53PM -0700, Kees Cook wrote:
> > >	1. Composed of pull requests sent directly to Linus
> > >
> > >	2. Contains branches destined for imminent inclusion by Linus
> >
> > But this means hours or a day or 2 at most.
>
> Yeah.

During the -rc cycles, sure.

However, folks have been consistently sending content for the next
release early - usually a week or two before the merge window even
opens.

For that matter, we've already seen pull requests destined for 6.13
getting pulled into linus-next.

> > >	3. Higher code quality expectation (these are pull requests that
> > >	maintainers expect Linus to pull)
> >
> > Are people putting things in linux-next that they don't expect to send to Linus? That seems like the greater problem.
>
> They shouldn't.  If they do we do indeed have a problem.

Not in the sense that it's not expected to be sent to Linus, but more in
the sense that folks are shoving things in -next before they passed all
the "local" tests a maintainer can run.

We end up with content that is destined to Linus, but is immature.

> > >	4. Continuous tree (not daily tags like in linux-next),
> > >	facilitating easier bisection
> >
> > I'm not sure how useful that is given the very small time window to find bugs.
>
> Same.
>
> > >The linus-next tree aims to provide a more stable and testable
> > >integration point compared to linux-next,
> >
> > Why not just use linux-next? I don't understand how this is any
> > different except that it provides very little time to do testing and
> > will need manual conflict resolutions that have already been done in
> > linux-next.
>
> Exactly!

We had multiple issues just this release cycle that would have been
caught by this tree and not by linux-next.

> > How about this, instead: no one sends -rc1 PRs to Linus that didn't go
> > through -next. Just have a bot that replies to all PRs with a health
> > check, and Linus can pull it if he thinks it looks good.
>
> Not just -rc1, otherwise agreed.
>
> > For example, for a given PR, the bot can report:
> >
> > - Were the patches CCed to a mailing list?
> > - A histogram of how long the patches were in next (to show bake times)
> > - Are any patches associated with test failures? (0day and many other
> > CIs are already running tests against -next; parse those reports)
> >
> > We could have a real pre-submit checker! :)
>
> That would be very useful.  Items 1 and 2 should be trivial, 3 would
> require a bit of work but would still be very useful.

We could add a report for the above, but:

1. Linus consistently pulls patches that haven't seen the light of day.
2. Linus explicitly objected to making a linux-next a must have.

So unless these results would be actually used, what's the point in
writing all of that?

--
Thanks,
Sasha