netdev - Re: [net-next PATCH] igb: update adapter stats when reading /proc/net/dev.

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Message-ID: <AANLkTi=+rkietX9jAMy5BRVwAENf-mK15py7y+LYQ-XJ@mail.gmail.com>
Date:	Tue, 5 Oct 2010 15:34:36 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Jesper Dangaard Brouer <hawk@...u.dk>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Jesper Dangaard Brouer <hawk@...x.dk>,
	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Carolyn Wyborny <carolyn.wyborny@...el.com>
Subject: Re: [net-next PATCH] igb: update adapter stats when reading /proc/net/dev.

On Tue, Oct 5, 2010 at 14:16, Jesper Dangaard Brouer <hawk@...u.dk> wrote:
> On Tue, 5 Oct 2010, Eric Dumazet wrote:
>
>> Le mardi 05 octobre 2010 à 17:19 +0200, Eric Dumazet a écrit :
>>>
>>> Le mardi 05 octobre 2010 à 16:53 +0200, Jesper Dangaard Brouer a écrit :
>>>
>>>> Its already racy, because "ethtool -S" reads out the stats immediately,
>>>> and thus races with the timer.
>>>>
>>>> See: igb_ethtool.c
>>>>  igb_get_ethtool_stats() invoke igb_update_stats(adapter);
>>>>
>>>
>>> You would be surprised how many bugs are waiting to be found and
>>> fixed ;)
>>
>> I took a look at igb stats, and it appears they also are racy on 32bit
>> arches. igb uses u64 counters, with no synchronization between
>> producers(writers) and consumers(readers).
>
> Are you saying, that we need more than a simple mutex in igb_update_stats()?
>
>
>> Some fixes are needed ;)
>
> The question is then if Intel wants to fix it, or let it be up to you or me?
>

I will make sure that Carolyn and Alex know about the issue.  But,
feel free to submit a patch if you guys have the time.

-- 
Cheers,
Jeff
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