netdev - Re: [PATCH net] net: sched: fix race condition in qdisc

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Date:   Sun, 20 Nov 2022 08:09:20 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Gal Pressman <gal@...dia.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Maxim Mikityanskiy <maximmi@...dia.com>,
        "David S . Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        Cong Wang <xiyou.wangcong@...il.com>, eric.dumazet@...il.com,
        syzbot <syzkaller@...glegroups.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Tariq Toukan <tariqt@...dia.com>,
        Maxim Mikityanskiy <maxtram95@...il.com>
Subject: Re: [PATCH net] net: sched: fix race condition in qdisc_graft()

On Sat, Nov 19, 2022 at 11:42 PM Gal Pressman <gal@...dia.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.