netdev - Re: [TEST] so_peek_off flakes on new NIPA systems

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Message-ID: <CAAVpQUC85zujcLMFKFh_+FtvFWcuPLqJQm=Gv0-4HuXkZWjQwQ@mail.gmail.com>
Date: Mon, 24 Nov 2025 11:04:02 -0800
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [TEST] so_peek_off flakes on new NIPA systems

On Mon, Nov 24, 2025 at 7:07 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> Hi Kuniyuki!
>
> We upgraded our system for NIPA recently to netdev foundation one
> (as you know). Looks like net/af_unix: so_peek_off is flaking
> on both debug and non-debug builds quite a lot with:
>
> # # so_peek_off.c:149:two_chunks_overlap_blocking:Expected -1 (-1) != bytes (-1)
> # # two_chunks_overlap_blocking: Test terminated by assertion
> # #          FAIL  so_peek_off.stream.two_chunks_overlap_blocking
>
> https://netdev-ctrl.bots.linux.dev/logs/vmksft/net-dbg/results/399761/134-so-peek-off/stdout

Thanks for the heads-up!

At this point, a fork()ed child/client is expected to send() data after
1ms while the parent/receiver process blocks at recv() up to 3ms, but
it seems recv() got -1 because fork()ed process was not scheduled
fast enough ?

Probably 3ms is too short when the host is overloaded.
I'll send a patch shortly with .gitignore updates.


>
> The newer system is 10-20% faster it's also moved from AWS Linux to
> Fedora. But I suspect the real reason is that our old system had
> quietly broken compilation of af_unix selftests
> because of Wflex-array-member-not-at-end which AWS Linux gcc doesn't
> understand:
>
> gcc: error: unrecognized command-line option ‘-Wflex-array-member-not-at-end’
> make: *** [../../lib.mk:222: /home/virtme/testing/wt-1/tools/testing/selftests/net/af_unix/diag_uid] Error 1

Oh well, maybe the package was gcc (11) instead of gcc14 ?
IIRC, Amazon Linux 2023 provides the newer one as a
namespaced package.

>
> So effectively we're been running some old copy of af_unix tests since
> this flag was added.

Yeah, apparently I no longer run tests on AL :p

and this is not a problem now on Fedora, right ?