From: Ding Tianhong <dingtianhong@huawei•com>
To: Nikolay Aleksandrov <nikolay@redhat•com>,
Eric Dumazet <eric.dumazet@gmail•com>
Cc: <netdev@vger•kernel.org>, <davem@davemloft•net>,
Jay Vosburgh <fubar@us•ibm.com>,
Andy Gospodarek <andy@greyhouse•net>,
Veaceslav Falico <vfalico@redhat•com>
Subject: Re: [PATCH net] bonding: fix two race conditions in bond_store_updelay/downdelay
Date: Thu, 14 Nov 2013 09:50:20 +0800 [thread overview]
Message-ID: <52842C5C.6080505@huawei.com> (raw)
In-Reply-To: <5283B19A.9050302@redhat.com>
On 2013/11/14 1:06, Nikolay Aleksandrov wrote:
> On 11/13/2013 06:03 PM, Eric Dumazet wrote:
>> On Wed, 2013-11-13 at 17:07 +0100, Nikolay Aleksandrov wrote:
>>> This patch fixes two race conditions between bond_store_updelay/downdelay
>>> and bond_store_miimon which could lead to division by zero as miimon can
>>> be set to 0 while either updelay/downdelay are being set and thus miss the
>>> zero check in the beginning, the zero div happens because updelay/downdelay
>>> are stored as new_value / bond->params.miimon. Use rtnl to synchronize with
>>> miimon setting.
>>
>> It seems a bit heavy duty to take rtnl for this.
>>
>> Using ACCESS_ONCE() in bonding_store_updelay()/bonding_store_downdelay()
>> should be enough ?
>>
>> int miimon = ACCESS_ONCE(bond->params.miimon);
>>
>>
>>
>> --
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>>
> Hi Eric,
> I thought about this version too, but downdelay/updelay can be changed in other
> places (e.g., store_miimon) and the resulting downdelay/updelay value might not
> be the right one.
> Correct me if I'm wrong, but this is what I have in mind (miimon = 100, updelay
> = 200):
> set miimon to 300 and concurrently set updelay to 400, we might endup leaving
> updelay to 400 because the old value of miimon is used in the calculation in
> store_updelay even though when changing miimon updelay/downdelay get adjusted,
> they might get adjusted by store_updelay/downdelay to a wrong value afterwards.
>
> Nik
>
>
agree, set miimon and set updelay may conflict.
>
>
> --
> To unsubscribe from this list: send the line "unsubscribe netdev" in
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>
>
next prev parent reply other threads:[~2013-11-14 1:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-13 16:07 [PATCH net] bonding: fix two race conditions in bond_store_updelay/downdelay Nikolay Aleksandrov
2013-11-13 16:34 ` Nikolay Aleksandrov
2013-11-13 17:03 ` Eric Dumazet
2013-11-13 17:06 ` Nikolay Aleksandrov
2013-11-13 17:38 ` Eric Dumazet
2013-11-14 1:50 ` Ding Tianhong [this message]
2013-11-14 10:17 ` Veaceslav Falico
2013-11-14 21:29 ` David Miller
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