netdev - Re: mmotm 2010-04-28

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Message-ID: <4BE82E73.9040709@trash.net>
Date:	Mon, 10 May 2010 18:04:03 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	David Miller <davem@...emloft.net>, Valdis.Kletnieks@...edu,
	akpm@...ux-foundation.org, peterz@...radead.org,
	linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
	netdev@...r.kernel.org, paulmck@...ux.vnet.ibm.com
Subject: Re: mmotm 2010-04-28 - RCU whinges

Patrick McHardy wrote:
> Eric Dumazet wrote:
>> Le lundi 10 mai 2010 à 17:40 +0200, Patrick McHardy a écrit :
>>> David Miller wrote:
>>>> From: Eric Dumazet <eric.dumazet@...il.com>
>>>> Date: Mon, 03 May 2010 07:43:56 +0200
>>>>
>>>>> Le lundi 03 mai 2010 à 07:41 +0200, Eric Dumazet a écrit :
>>>>>
>>>>>> Oops scratch that, I'll resend a correct version.
>>>>>>
>>>>>>
>>>>> Sorry, patch _is_ fine, I had one brain collapse when re-reading it, I
>>>>> thought a different mutex was in use in one of the functions.
>>>> Ok, Patrick please review, thanks.
>>> Actually we don't need the rcu_dereference() calls at all since
>>> registration and unregistration are protected by the mutexes.
>>>
>>> I queued this patch in nf-next, the only reason why I haven't
>>> submitted it yet is that I was unable to get git to cleanly export
>>> only the proper set of patches meant for -next due to a few merges,
>>> it insists on including 5 patches already merged upstream. If you
>>> don't mind ignoring the first 5 patches in the series, I'll send a
>>> pull request tonight.
>>>
>> This will clash with upcoming RCU patches, where rcu protected pointer
>> cannot be directly accessed without lockdep splats.
>>
>> We will need one day or another a rcu_...(nf_conntrack_event_cb)
> 
> Thanks for the information, I didn't realize that when looking at
> those patches. So I guess the correct fix once those patches are
> merged would be to use rcu_assign_protected() and rcu_access_pointer().

Ah, and that's what you did. Sorry for the confusion :)
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