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From: Herbert Xu on 13 Aug 2010 14:00
On Fri, Aug 13, 2010 at 09:29:12AM -0700, Paul E. McKenney wrote:
>
> > But this doesn't really solve the problem for netif_rx. The reason
> > is that netif_rx can either be called with IRQs on OR off. So we
> > need to take the right precautions in the case where IRQs are
> > enabled along with BH.
>
> Interesting...
>
> Is it possible that IRQs are off at rcu_read_lock_bh_irqsoff() time, but
> enabled by the time we get to rcu_read_unlock_bh_irqsoff()? I hope not,
> but have to ask. If I am guaranteed of the same state in both cases,
> I can do something like the following:

Yes in our case it's certainly guaranteed that IRQs will remain
off.

> But all in all, mightn't it be easier to remove the checks from
> _local_bh_enable(), and then just use rcu_read_lock_bh()? Have those
> checks really been that helpful in finding bugs? ;-)

You are right. It would be much simpler to simply have it not
warn.

Cheers,
--
Email: Herbert Xu <herbert(a)gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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