netdev - Re: [PATCH net] packet: Do not call fanout

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Date:   Wed, 15 Feb 2017 16:33:50 +0000
From:   Anoob Soman <anoob.soman@...rix.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
CC:     <netdev@...r.kernel.org>, <davem@...emloft.net>
Subject: Re: [PATCH net] packet: Do not call fanout_release from atomic
 contexts

On 15/02/17 13:46, Eric Dumazet wrote:
> On Wed, 2017-02-15 at 11:07 +0000, Anoob Soman wrote:
>> On 13/02/17 14:50, Anoob Soman wrote:
>>> On 13/02/17 14:26, Eric Dumazet wrote:
>>>> On Mon, 2017-02-13 at 13:28 +0000, Anoob Soman wrote:
>>>>
>>>>> Wouldn't it be easier to call synchronize_net(), before calling
>>>>> fanout_release_data() and kfree(f).
>>>>> The behavior, wrt synchronize_net, would be same as before and
>>>>> fanout_release() will cleanup everything without leaving any residue.
>>>> So we would require two synchronize_net() calls instead of one ?
>>>>
>>>> synchronize_net() is very expensive on some hosts, it is a big hammer.
>>>>
>>>>
>>>>
>>> Yes, one before fanout_release_data() (will be called only if
>>> fanout->sk_ref == 0) and one after fanout_release().
>>>
>>> I understand synchronize_net() is expensive, but adding another
>>> synchronize_net(),  before fanout_release_data(), will be no different
>>> from what we have in the existing code.
>>>
>>> I can also make sure second synchronize_net() doesn't get called
>>> again, if fanout_release() calls synchronize_net(), by making
>>> fanout_release() return something to indicate it has done
>>> synchronize_net().
>> Hi Eric,
>>
>> Did you get a chance to looks at my comments ?
> You misunderstood my suggestion.
>
> I simply suggested to move the code, not adding another
> synchronize_net()
>

I will move the code and send a v2.