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References: <20221018203258.2793282-1-edumazet@google.com> <162f9155-dfe3-9d78-c59f-f47f7dcf83f5@nvidia.com>
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In-Reply-To: <9f4c2ca9-bc6d-f2bf-6c03-e95affb55aae@nvidia.com>
From:   Eric Dumazet <edumazet@google.com>
Date:   Sun, 20 Nov 2022 08:09:20 -0800
Message-ID: <CANn89iJkdQ9eBkwmWMcf7uKwB=cY8hbwo2Jqdtwo3mpjswAFHg@mail.gmail.com>
Subject: Re: [PATCH net] net: sched: fix race condition in qdisc_graft()
To:     Gal Pressman <gal@nvidia.com>
Cc:     Jakub Kicinski <kuba@kernel.org>,
        Maxim Mikityanskiy <maximmi@nvidia.com>,
        "David S . Miller" <davem@davemloft.net>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
        Cong Wang <xiyou.wangcong@gmail.com>, eric.dumazet@gmail.com,
        syzbot <syzkaller@googlegroups.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Tariq Toukan <tariqt@nvidia.com>,
        Maxim Mikityanskiy <maxtram95@gmail.com>
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On Sat, Nov 19, 2022 at 11:42 PM Gal Pressman <gal@nvidia.com> wrote:
>
> On 10/11/2022 11:08, Gal Pressman wrote:
> > On 06/11/2022 10:07, Gal Pressman wrote:

> >> It reproduces consistently:
> >> ip link set dev eth2 up
> >> ip addr add 194.237.173.123/16 dev eth2
> >> tc qdisc add dev eth2 clsact
> >> tc qdisc add dev eth2 root handle 1: htb default 1 offload
> >> tc class add dev eth2 classid 1: parent root htb rate 18000mbit ceil
> >> 22500.0mbit burst 450000kbit cburst 450000kbit
> >> tc class add dev eth2 classid 1:3 parent 1: htb rate 3596mbit burst
> >> 89900kbit cburst 89900kbit
> >> tc qdisc delete dev eth2 clsact
> >> tc qdisc delete dev eth2 root handle 1: htb default 1
> >>
> >> Please let me know if there's anything else you want me to check.
> > Hi Eric, did you get a chance to take a look?
>
> No response for quite a long time, Jakub, should I submit a revert?

Sorry, I won't have time to look at this before maybe two weeks.

If you want to revert a patch which is correct, because some code
assumes something wrong,
I will simply say this seems not good.

I think this offload code path needs more care from nvidia folks.