netdev - Re: [PATCH] niu: fix SMP race protecting rx_rings and tx

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Message-Id: <20110203.155313.115940720.davem@davemloft.net>
Date:	Thu, 03 Feb 2011 15:53:13 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	fleitner@...hat.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] niu: fix SMP race protecting rx_rings and tx_rings

From: Flavio Leitner <fleitner@...hat.com>
Date: Thu, 3 Feb 2011 21:47:48 -0200

> On Thu, Feb 03, 2011 at 03:22:14PM -0800, David Miller wrote:
>> One thing I'm worried about with your patch is that the statistics
>> method can be called in basically any context, therefore a sleeping
>> lock like the rw_semaphore is probably not usable.
>> 
>> In fact I'm going to revert your patch for now because of this issue.
> 
> Oops, I didn't see it there.  I thought all calls there were process
> context.  Anyway, RCU then...

Yes, one example is the dev_get_stats() call made in
drivers/net/bonding/bond_main.c, which occurs with a
rw spinlock held and BH disabled.

> thanks for reviewing it,

No problem.  I think I even have a way to fix this without using RCU
(directly).  Just some memory barriers during allocation of the
channels.

I'll post the patch after I'm done with it, thanks again Falvio.
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