[TEST] so_peek_off flakes on new NIPA systems

[TEST] so_peek_off flakes on new NIPA systems

[Jakub Kicinski]

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

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

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

Re: [TEST] so_peek_off flakes on new NIPA systems

[Kuniyuki Iwashima]

On Mon, Nov 24, 2025 at 7:07 AM Jakub Kicinski <kuba@kernel.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 ?

Re: [TEST] so_peek_off flakes on new NIPA systems

[Jakub Kicinski]

On Mon, 24 Nov 2025 11:04:02 -0800 Kuniyuki Iwashima wrote:
> > 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 ?

Right, not a problem for us any more.
I was just explaining why we're hitting it now.