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Date: Fri, 16 Dec 2011 14:05:59 +0400
From: Glauber Costa <glommer@parallels.com>
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To: Eric Dumazet <eric.dumazet@gmail.com>
CC: <davem@davemloft.net>, <linux-kernel@vger.kernel.org>,
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        <cgroups@vger.kernel.org>, Stephen Rothwell <sfr@canb.auug.org.au>,
        Randy Dunlap <rdunlap@xenotime.net>
Subject: Re: [PATCH v2] net: fix sleeping while atomic problem in sock mem_cgroup.
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On 12/16/2011 02:04 PM, Eric Dumazet wrote:
> Le vendredi 16 décembre 2011 à 13:53 +0400, Glauber Costa a écrit :
>> On 12/16/2011 01:31 PM, Eric Dumazet wrote:
>>> Le vendredi 16 décembre 2011 à 13:09 +0400, Glauber Costa a écrit :
>>>> Since we can't scan the proto_list to initialize sock cgroups, as it
>>>> holds a rwlock, and we also want to keep the code generic enough to
>>>> avoid calling the initialization functions of protocols directly,
>>>> I propose we keep the interested parties in a separate list. This list
>>>> is protected by a mutex so we can sleep and do the necessary allocations.
>>>>
>>>> Also fixes a reference problem found by Randy Dunlap's randconfig.
>>>>
>>>> Signed-off-by: Glauber Costa<glommer@parallels.com>
>>>> CC: Hiroyouki Kamezawa<kamezawa.hiroyu@jp.fujitsu.com>
>>>> CC: David S. Miller<davem@davemloft.net>
>>>> CC: Eric Dumazet<eric.dumazet@gmail.com>
>>>> CC: Stephen Rothwell<sfr@canb.auug.org.au>
>>>> CC: Randy Dunlap<rdunlap@xenotime.net>
>>>> ---
>>>
>>> Sorry to come late, but why dont we convert proto_list_lock to a mutex ?
>>
>> I didn't suggest this, as I imagined there could be some performance
>> implications to be drawn from it that may not be obvious to me.
>>
>> But if it is okay with you net guys, it is certainly okay with me as well.
>
> This 'lock' is not performance sensitive, its very seldom taken.
>
> If we really wanted to be fast, it would not be a rwlock anymore ;)
>
> "cat /proc/net/protocols" could eventually use RCU locking if we want
> parallelism. (I dont think its needed)
>

Well, in this case, I myself think this is a better solution. Do you 
want to push the patch yourself, or should I do it ?