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

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Date:	Mon, 11 Feb 2008 23:49:24 +0100
From:	Jarek Poplawski <jarkao2@...il.com>
To:	James Chapman <jchapman@...alix.com>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH][PPPOL2TP]: Fix SMP oops in pppol2tp driver

On Mon, Feb 11, 2008 at 10:19:35PM +0000, James Chapman wrote:
...
> Below is example output from lockdep. The oops is reproducible when  
> creating/deleting lots of sessions while passing data. The lock is being  
> acquired for read and write in softirq contexts.
>
> Is there a better way to fix this?
>
> =================================
> [ INFO: inconsistent lock state ]
> 2.6.24-core2 #1
> ---------------------------------
> inconsistent {in-softirq-R} -> {softirq-on-W} usage.
> openl2tpd/3215 [HC0[0]:SC0[0]:HE1:SE1] takes:
>   (&tunnel->hlist_lock){---?}, at: [<f8eea157>]
> pppol2tp_connect+0x517/0x6d0 [pppol2tp]
> {in-softirq-R} state was registered at:

IMHO, according to this, disabling bh should be enough. And if it's
like in this report: only read_lock is taken from softirqs, then this
should be necessary to change only all write_locks to write_lock_bh
(of course unless somewhere bhs are disabled already). Unless I miss
something?!

Cheers,
Jarek P.
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