netdev - Re: netif_napi_add vs. multiple netdev's

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Date:	Tue, 16 Oct 2007 16:37:24 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	David Miller <davem@...emloft.net>
Cc:	benh@...nel.crashing.org, netdev@...r.kernel.org
Subject: Re: netif_napi_add vs. multiple netdev's

On Tue, 16 Oct 2007 15:16:16 -0700 (PDT)
David Miller <davem@...emloft.net> wrote:

> From: Stephen Hemminger <shemminger@...ux-foundation.org>
> Date: Tue, 16 Oct 2007 09:10:35 -0700
> 
> > On Tue, 16 Oct 2007 15:47:13 +1000
> > Benjamin Herrenschmidt <benh@...nel.crashing.org> wrote:
> > 
> > > The way it's currently implemented, there's a list of NAPI's attached to
> > > the netdev, so obviously, that won't work for my usage scenario.
> > 
> > sky2 driver has potentially 2 ports for 1 NAPI instance.
> 
> And it's unfortunately buggy.
> 
> For example, the sky2_suspend() code iterates over the ports
> and calls sky2_down() on each one that is up.
> 
> That will call napi_disable() on the same NAPI instance if
> multiple ports are up, and thus hang the machine.
> 
> This is why, Stephen, for the second time, I'm telling you
> that perhaps you should put the NAPI instance into the
> sky2_port struct.

It isn't possible, there is only one hardware IRQ, and one
common status buffer.  I'll fix the suspend code, it has other
problems as well.

-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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