netdev - Re: [Bug #14925] sky2 panic under load

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Message-ID: <20100112085633.GB6628@ff.dom.local>
Date:	Tue, 12 Jan 2010 08:56:34 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	shemminger@...tta.com, mikem@...g3k.org, flyboy@...il.com,
	rjw@...k.pl, netdev@...r.kernel.org,
	Michael Breuer <mbreuer@...jas.com>
Subject: Re: [Bug #14925] sky2 panic under load

On Tue, Jan 12, 2010 at 12:08:04AM -0800, David Miller wrote:
> From: Jarek Poplawski <jarkao2@...il.com>
> Date: Tue, 12 Jan 2010 07:50:59 +0000
> 
> > I think, I can see similar problems e.g. in gianfar or netxen, where
> > napi_disable() is done after netif_device_detach(), especially in
> > suspend procedures (there might be less severe (than oops) effects
> > yet). IMHO, it all looks simply error prone (sometime you have to
> > know a driver well to track all possible paths to say it's really
> > safe).
> 
> Then that's an even larger bug.
> 
> Until you do napi_disable(), the device can be touched.
> 
> Asynchronous paths outside of the driver's control, even
> with interrupts disabled, can call back into the driver
> and touch the chip.
> 
> F.e. netpoll via netconsole output on another cpu
> 
> So it therefore must be done before doing the actual work of bringing
> the device down or suspending it.

Maybe I miss something, but once more: this patch mentioned by Berck
Nash has been tested by at least two users, Berck himself, and
probably even more intensively by Michael Breuer, during af_packet
debugging. Both guys acknowledged it helped, so it can't be that bad.

Jarek P.
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