netdev - Re: [PATCH net v2 2/2] tuntap: correctly add the missing xdp flush

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Message-ID: <f8e1961b-8fbc-1511-7854-487051233931@redhat.com>
Date:   Thu, 22 Feb 2018 17:35:02 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     mst@...hat.com, christoffer.dall@...aro.org
Subject: Re: [PATCH net v2 2/2] tuntap: correctly add the missing xdp flush



On 2018年02月22日 15:54, Sergei Shtylyov wrote:
> Hello!
>
> On 2/22/2018 9:24 AM, Jason Wang wrote:
>
>> Commit 762c330d670e ("tuntap: add missing xdp flush") tries to fix the
>> devmap stall caused by missed xdp flush by counting the pending xdp
>> redirected packets and flush when it exceeds NAPI_POLL_WEIGHT or
>> MSG_MORE is clear. This may lead BUG() since xdp_do_flush() was
>
>    Lead to BUG().
>
>> called under process context with preemption enabled. Simply disable
>
>    s/under/in the/?
>
>> preemption may silent the warning but be not enough since process may
>
>    Silence.
>
>> move between different CPUS during a batch which cause xdp_do_flush()
>> misses some CPU where the process run previously. Consider the several
>> fallouts, that commit was reverted. To fix the issue correctly, we can
>> simply calling xdp_do_flush() immediately after xdp_do_redirect(),
>
>    Call.
>
>> a side effect is that this removes any possibility of batching which
>> could be addressed in the future.
>>
>> Reported-by: Christoffer Dall <christoffer.dall@...aro.org>
>> Fixes: 762c330d670e ("tuntap: add missing xdp flush")
>> Signed-off-by: Jason Wang <jasowang@...hat.com>
> [...]
>
> MBR, Sergei

My bad, let me post v3.

Thanks