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From:   Eric Dumazet <edumazet@google.com>
Date:   Tue, 10 Oct 2023 19:24:08 +0200
Message-ID: <CANn89iJ_KMA=dQWPhU8WQBc0_CvUztUBodAf-cW-2F=HMX3HJg@mail.gmail.com>
Subject: Re: [PATCH 6.1 000/162] 6.1.57-rc1 review
To:     Matthieu Baerts <matttbe@kernel.org>
Cc:     Naresh Kamboju <naresh.kamboju@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, patches@lists.linux.dev,
        linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
        akpm@linux-foundation.org, linux@roeck-us.net, shuah@kernel.org,
        patches@kernelci.org, lkft-triage@lists.linaro.org, pavel@denx.de,
        jonathanh@nvidia.com, f.fainelli@gmail.com,
        sudipm.mukherjee@gmail.com, srw@sladewatkins.net, rwarsow@gmx.de,
        conor@kernel.org, "David S. Miller" <davem@davemloft.net>,
        David Ahern <dsahern@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        MPTCP Upstream <mptcp@lists.linux.dev>
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On Tue, Oct 10, 2023 at 6:51=E2=80=AFPM Matthieu Baerts <matttbe@kernel.org=
> wrote:
>
> Hi Naresh,
>
> On 09/10/2023 22:43, Naresh Kamboju wrote:
> > On Mon, 9 Oct 2023 at 18:46, Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> >>
> >> This is the start of the stable review cycle for the 6.1.57 release.
> >> There are 162 patches in this series, all will be posted as a response
> >> to this one.  If anyone has any issues with these being applied, pleas=
e
> >> let me know.
> >>
> >> Responses should be made by Wed, 11 Oct 2023 13:00:55 +0000.
> >> Anything received after that time might be too late.
> >>
> >> The whole patch series can be found in one patch at:
> >>         https://www.kernel.org/pub/linux/kernel/v6.x/stable-review/pat=
ch-6.1.57-rc1.gz
> >> or in the git tree and branch at:
> >>         git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-sta=
ble-rc.git linux-6.1.y
> >> and the diffstat can be found below.
> >>
> >> thanks,
> >>
> >> greg k-h
> >
> >
> > The following kernel warnings were noticed several times on arm x15 dev=
ices
> > running stable-rc 6.1.57-rc1 while running  selftests: net: mptcp_conne=
ct.sh
> > and netfilter: nft_fib.sh.
> >
> > The possible unsafe locking scenario detected.
> >
> > FYI,
> > Stable-rc/ linux.6.1.y kernel running stable/ linux.6.5.y selftest in t=
his case.
> >
> > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> >
> > kselftest: Running tests in net/mptcp
>
> Thank you for having reported the issue and having added MPTCP ML in Cc!
>
> Just to avoid confusions: the "WARNING" you shared when running
> 'mptcp_connect.sh' selftest appeared before creating the first MPTCP
> connection. It looks like there is no reference to MPTCP in the
> calltraces. Also, because you have the same issue with nft_fib.sh, I
> would say that this issue is not linked to MPTCP but rather to a recent
> modification in the IPv6 stack.
>
> By chance, did you start a "git bisect" to identify the commit causing
> this issue?
>
>

I think stable teams missed to backport

commit c486640aa710ddd06c13a7f7162126e1552e8842
Author: Eric Dumazet <edumazet@google.com>
Date:   Mon Mar 13 20:17:32 2023 +0000

    ipv6: remove one read_lock()/read_unlock() pair in rt6_check_neigh()

    rt6_check_neigh() uses read_lock() to protect n->nud_state reading.

    This seems overkill and causes false sharing.

    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reviewed-by: David Ahern <dsahern@kernel.org>
    Reviewed-by: Martin KaFai Lau <martin.lau@kernel.org>
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>