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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     Daniel Vetter <daniel.vetter@ffwll.ch>
CC:     Mark Brown <broonie@kernel.org>,
        "Theodore Y. Ts'o" <tytso@mit.edu>,
        "ksummit-discuss@lists.linuxfoundation.org" 
        <ksummit-discuss@lists.linuxfoundation.org>,
        Greg KH <gregkh@linuxfoundation.org>, "w@1wt.eu" <w@1wt.eu>,
        "julia.lawall@lip6.fr" <julia.lawall@lip6.fr>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [Ksummit-discuss] bug-introducing patches
Thread-Topic: [Ksummit-discuss] bug-introducing patches
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Date:   Wed, 2 May 2018 19:46:34 +0000
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On Wed, May 02, 2018 at 10:11:14AM +0200, Daniel Vetter wrote:
>On Tue, May 1, 2018 at 11:15 PM, Mark Brown <broonie@kernel.org> wrote:
>> On Tue, May 01, 2018 at 04:54:48PM -0400, Theodore Y. Ts'o wrote:
>>> I do think it's about AUTOSEL, because when I'm dealing with a
>>> regression, I want to get it fixed fast.  Because the alternative is
>>> the merge-window commit getting reverted.  AUTOSEL seems wants perfect
>>> patches that it can cherry pick once, as opposed to a case where if the
>>> user confirms that it fixes the regression, I want to send it to Linus
>>> quickly.  I do *not* want it to marinate in linux-next for 1-2 weeks.
>>> I would much rather that *stable* hold off on picking up the patch for
>>> 1-2 weeks, but get it fixed in Linux HEAD sooner.  If that means that
>>> the regression fix needs a further clean up, so be it.
>>
>> We've had issues with the automated testing systems in the past where a
>> maintainer has had a policy of letting things percoltate for a week
>> before sending to Linus and there's been a bug that caused a substantial
>> set of tests to fail to run (generally it's something that had unnoticed
>> dependencies in -next so wasn't caught there) - we essentially end up
>> not getting the affected bits of test coverage for that period of time
>> which is not helpful.
>
>So much agreed. For our CI we carry a constantly rolling set of fixup
>patches to keep it working, because regression fixes sometimes take
>too long. And too long here for our needs is measured in days/hours -
>developers start screaming pretty much immediately when our CI is down
>:-)
>
>Ofc I prefer if all subsystems ramp up pre-merge testing as much as
>possible (and with xfstests and stuff like that I think filesystems
>are leading here, if not consistently). But given the huge scope of
>the kernel we'll never reach 100%, and oddball regressions will be
>inevitable. Once a regression has crept through it imo really should
>get fixed asap, with no unecessary soaking times - get a better
>CI/kerneltests in place if you feel like you need to soak stuff.

Oh I agree with what you're saying, if you have a good testing setup
this is (usually) much better than just throwing stuff in -next, so I
didn't mean to force soaking every fix in -next for a few weeks.

As you said, the regression should be fixed "asap", not "immediately".
It should go through some sort of review and testing the maintainers are
happy with, but unfourtenately it doesn't happen now.=