netdev - Re: [PATCH 0/3] selftests/bpf: Fix a few issues in arena_spin

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Message-ID: <CAADnVQ++W2vQTZgzQk4Ruj7E68DcA4WS=q=GV-dF4kTvcJd83g@mail.gmail.com>
Date: Fri, 25 Apr 2025 17:32:37 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Konstantin Ryabitsev <konstantin@...uxfoundation.org>
Cc: patchwork-bot+netdevbpf@...nel.org, Jakub Kicinski <kuba@...nel.org>, 
	Ilya Leoshkevich <iii@...ux.ibm.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, bpf <bpf@...r.kernel.org>, 
	Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
	Alexander Gordeev <agordeev@...ux.ibm.com>, Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH 0/3] selftests/bpf: Fix a few issues in arena_spin_lock

On Fri, Apr 25, 2025 at 11:58 AM Konstantin Ryabitsev
<konstantin@...uxfoundation.org> wrote:
>
> On Thu, Apr 24, 2025 at 11:41:16AM -0700, Alexei Starovoitov wrote:
> > > On Thu, 24 Apr 2025 18:41:24 +0200 you wrote:
> > > > Hi,
> > > >
> > > > I tried running the arena_spin_lock test on s390x and ran into the
> > > > following issues:
> > > >
> > > > * Changing the header file does not lead to rebuilding the test.
> > > > * The checked for number of CPUs and the actually required number of
> > > >   CPUs are different.
> > > > * Endianness issue in spinlock definition.
> > > >
> > > > [...]
> > >
> > > Here is the summary with links:
> > >   - [1/3] selftests/bpf: Fix arena_spin_lock.c build dependency
> > >     https://git.kernel.org/netdev/net-next/c/4fe09ff1a54a
> > >   - [2/3] selftests/bpf: Fix arena_spin_lock on systems with less than 16 CPUs
> > >     (no matching commit)
> > >   - [3/3] selftests/bpf: Fix endianness issue in __qspinlock declaration
> > >     (no matching commit)
> >
> > Hmm. Looks like pw-bot had too much influence from AI bots
> > and started hallucinating itself :)
>
> Looks like it's a mix of bad assumptions and the usual difficulty of
> recognizing fast-forward merges that came in through a different tree.
>
> If you look at the commit mentioned above, it has:
>
> | Note that the first patch in this series is a leftover from an
> | earlier patchset that was abandoned:
> | Link: https://lore.kernel.org/netdev/20250129004337.36898-2-shannon.nelson@amd.com/
>
> This confuses the bot into thinking that the linked message is the source of
> the patch (which is why we started using patch.msgid.link to disambiguate
> links aimed at cross-referencing and links aimed at indicating commit
> provenance -- but we aren't relying on this disambiguation in the bot itself
> yet).

Thanks for investigating. The above part is clear,
but I still don't understand what was so special about Ilya's
patch that only his first patch in the series became a victim.
msgid-s are completely different.

> The other replies are the usual mess when fast-forward tree updates confuse
> things. It's a long-standing hard bug to fix.
>
> I am going to re-enable the bot for now -- in general it's not any more wrong
> than usual.

Makes sense. Better to have it flaky than none at all.

> I'm scheduling some time next week to try to tackle the
> fast-forwards problem.

Thanks. That would be great.