linux-kernel - Re: orinoco driver causes *lots* of lockdep spew

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Date:	Fri, 4 Aug 2006 11:05:50 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	Arjan van de Ven <arjan@...radead.org>, davej@...hat.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	davem@...emloft.net, linville@...driver.com, jt@....hp.com
Subject: Re: orinoco driver causes *lots* of lockdep spew

On Thu, Aug 03, 2006 at 08:22:58AM -0700, Arjan van de Ven wrote:
>
> however I'm not quite yet convinced that this patch is going to solve
> this particular deadlock.
> (I agree with the principle of it and I think it's really needed,
> I just don't yet see how it's going to solve this specific deadlock. But
> then again it's early and I've not had sufficient coffee yet so I could
> well be wrong)

Well it solves the dead lock by breaking the chain that links the
netlink system with the jungle of wireless locking :)

The spin lock in sk_buff_head acts as a mediator.  We only feed the
skb to the netlink system once that spin lock has been dropped.
 
> it's not just about irq context, it's about being called with any lock 
> that's
> used in IRQ context; that is what makes this double nasty...

Yes it is nasty.  However, so far wireless seems to be the only offender.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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