linux-kernel - Re: [PATCH net v3] net: openvswitch: fix race on port output

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Message-ID: <CANn89i++9qYyhbh30RPqabeTbBbUHdAv+0YP0Z01pbMm1+nt5A@mail.gmail.com>
Date:   Fri, 7 Apr 2023 10:48:18 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Felix Huettner <felix.huettner@...l.schwarz>
Cc:     netdev@...r.kernel.org, dev@...nvswitch.org,
        linux-kernel@...r.kernel.org, pabeni@...hat.com, kuba@...nel.org,
        pshelar@....org, davem@...emloft.net, luca.czesla@...l.schwarz
Subject: Re: [PATCH net v3] net: openvswitch: fix race on port output

On Wed, Apr 5, 2023 at 9:53 AM Felix Huettner
<felix.huettner@...l.schwarz> wrote:
>
> assume the following setup on a single machine:
> 1. An openvswitch instance with one bridge and default flows
> 2. two network namespaces "server" and "client"
> 3. two ovs interfaces "server" and "client" on the bridge
> 4. for each ovs interface a veth pair with a matching name and 32 rx and
>    tx queues
> 5. move the ends of the veth pairs to the respective network namespaces
> 6. assign ip addresses to each of the veth ends in the namespaces (needs
>    to be the same subnet)
> 7. start some http server on the server network namespace
> 8. test if a client in the client namespace can reach the http server
>
> when following the actions below the host has a chance of getting a cpu
> stuck in a infinite loop:
> 1. send a large amount of parallel requests to the http server (around
>    3000 curls should work)
> 2. in parallel delete the network namespace (do not delete interfaces or
>    stop the server, just kill the namespace)
>
> there is a low chance that this will cause the below kernel cpu stuck
> message. If this does not happen just retry.
> Below there is also the output of bpftrace for the functions mentioned
> in the output.
>
...
Reviewed-by: Eric Dumazet <edumazet@...gle.com>