netdev - Re: [PATCH][PPPOL2TP]: Fix SMP oops in pppol2tp driver

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Date:	Tue, 19 Feb 2008 09:09:38 +0000
From:	James Chapman <jchapman@...alix.com>
To:	Jarek Poplawski <jarkao2@...il.com>
CC:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH][PPPOL2TP]: Fix SMP oops in pppol2tp driver

Jarek Poplawski wrote:
> On Mon, Feb 18, 2008 at 10:09:24PM +0000, James Chapman wrote:
>> Jarek Poplawski wrote:
>>> Hi,
>>>
>>> It seems, this nice report is still uncomplete: could you check if
>>> there could have been something more yet?
>> Unfortunately the ISP's syslog stops. But I've been able to borrow two
>> Quad Xeon boxes and have reproduced the problem.
>>
>> Here's a new version of the patch. The patch avoids disabling irqs and
>> fixes the sk_dst_get() usage that DaveM mentioned. But even with this
>> patch, lockdep still complains if hundreds of ppp sessions are inserted
>> into a tunnel as rapidly as possible (lockdep trace is below). I can
>> stop these errors by wrapping the call to ppp_input() in
>> pppol2tp_recv_dequeue_skb() with local_irq_save/restore. What is a
>> better fix?
> 
> Hmm... This is a really long report and quite a bit different from
> the previous one. I need some time for this. BTW: you sent before a
> lockdep report with hlist_lock problem. I think this could be fixed
> in some independent patch to make this all more readable. Are all
> the other changes in this current patch only because of this or
> previous lockdep report or for some other reasons (or reports) yet?

As I mentioned in my reply to davem, modifying the pppol2tp driver as 
described in the patch I sent made the original lockdep problems go away.


-- 
James Chapman
Katalix Systems Ltd
http://www.katalix.com
Catalysts for your Embedded Linux software development

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