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Date:   Mon, 14 May 2018 10:12:37 +0200
From:   Boris Brezillon <boris.brezillon@bootlin.com>
To:     Geert Uytterhoeven <geert@linux-m68k.org>
Cc:     Sasha Levin <Alexander.Levin@microsoft.com>,
        "ksummit-discuss@lists.linuxfoundation.org" 
        <ksummit-discuss@lists.linuxfoundation.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "w@1wt.eu" <w@1wt.eu>
Subject: Re: [Ksummit-discuss] bug-introducing patches
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On Mon, 14 May 2018 10:00:30 +0200
Geert Uytterhoeven <geert@linux-m68k.org> wrote:

> On Tue, May 1, 2018 at 10:00 PM, Sasha Levin
> <Alexander.Levin@microsoft.com> wrote:
> > On Tue, May 01, 2018 at 03:44:50PM -0400, Theodore Y. Ts'o wrote:  
> >>On Tue, May 01, 2018 at 04:38:21PM +0000, Sasha Levin wrote:  
> >>>  - A merge window commit spent 50% more days, on average, in -next than a -rc
> >>>    commit.  
> >>
> >>So it *used* to be the case that after the merge window, I would queue
> >>up bug fixes for the next merge window.  Greg K-H pushed for me to
> >>send them to Linus sooner, instead of waiting for the next merge
> >>window.  TBH, it's actually easier for me to just wait until the next
> >>merge window, but please understand that there are multiple pressures
> >>on maintainers going on here, and the latest efforts to try to use
> >>AUTOSEL is just the most recent pressure placed on maintainers.
> >>
> >>The other thing is that when there is a regression users who are
> >>testing linux-next want it fixed *fast*.  That's considered more
> >>important to them than waiting for one, perfect patch, just to keep
> >>AUTOSEL happy.
> >>
> >>So please understand that when you say that maintainers *need* to do X
> >>or Y, that there you are not the only one standing in line putting
> >>pressures on maintainers saying they *need* to do something.  And
> >>quite frankly, I consider keeping people who are nice enough to test
> >>linux-next happy to be **far** more important than AUTOSEL.  
> >
> > Ted,
> >
> > I'm not at all asking to wait before adding the patches to your tree,
> > or to -next. I'm asking to hold on to them a bit longer before you
> > push them to Linus because I can show that patches that don't spend
> > enough time in -next are more likely to introduce bugs.
> >
> > Yes, linux-next users want it fixed *now* and I completely agree it
> > should be done that way, but the fix should not be immediately pushed to
> > Linus as well.
> >
> > I've just finished reading an interesting article on LWN about the
> > PostgreSQL fsync issues (https://lwn.net/Articles/752952/). If you
> > look at Willy's commit, he wrote the final version of it about 5 days
> > ago, Jeff merged it in 3 days ago, and Linus merged it in the tree
> > today. Did it spend any time getting -next testing? nope.
> >
> > What's worse is that that commit is tagged for stable, which means
> > that (given Greg's schedule) it may find it's way to -stable users
> > even before some -next users/bots had a chance to test it out.  
> 
> I just noticed a case where a commit was picked up for stable, while a
> bot had flagged it as a build regression 18 hours earlier (with a CC to
> lkml).

Also, this patch has been on a tree that I know is tested by Fengguang's
robots for more than a week (and in linux-next for 2 days, which, I
agree, is probably not enough), and still, I only received the bug
report when the patch reached mainline. Are there tests that are only
run on Linus' tree?

> 
> So it looks like the script for backporting commits should be enhanced to
> check for this (searching for the commit ID in my email archive found the
> bot report).
> 
> Thanks!
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
>