netdev - Re: [PATCH 12/14] Spidernet Avoid possible RX chain corruption

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Message-Id: <1166147307.4892.16.camel@concordia.ozlabs.ibm.com>
Date:	Fri, 15 Dec 2006 12:48:27 +1100
From:	Michael Ellerman <michael@...erman.id.au>
To:	Linas Vepstas <linas@...tin.ibm.com>
Cc:	Andrew Morton <akpm@...l.org>, Arnd Bergmann <arnd@...db.de>,
	netdev@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
	linuxppc-dev@...abs.org, Jens Osterkamp <Jens.Osterkamp@....de>,
	jgarzik@...ox.com, James K Lewis <jim@...ewis.com>
Subject: Re: [PATCH 12/14] Spidernet Avoid possible RX chain corruption

On Thu, 2006-12-14 at 11:15 -0600, Linas Vepstas wrote:
> On Thu, Dec 14, 2006 at 11:22:43AM +1100, Michael Ellerman wrote:
> > >  	spider_net_refill_rx_chain(card);
> > > -	spider_net_enable_rxchtails(card);
> > >  	spider_net_enable_rxdmac(card);
> > >  	return 0;
> > 
> > Didn't you just add that line?
> 
> Dagnabbit. The earlier pach was moving around existing code.
> Or, more precisely, trying to maintain the general function
> of the old code even while moving things around.
> 
> Later on, when I started looking at what the danged function 
> actually did, and the context it was in, I realized that it 
> was a bad idea to call the thing.  So then I removed it. :-/
> 
> How should I handle this proceedurally? Resend the patch sequence? 
> Let it slide?

If it was my code I'd redo the series, it's confusing and it's going to
look confused in the git history IMHO.

Currently the driver calls spider_net_enable_rxchtails() from
spider_net_enable_card() and spider_net_handle_rxram_full().

Your patch 3/14 removes spider_net_handle_rxram_full() entirely, leaving
spider_net_enable_card() as the only caller of
spider_net_enable_rxchtails().

Patch 10/14 adds a call to spider_net_enable_rxchtails() in
spider_net_alloc_rx_skbs(), and nothing else (except comment changes).

Patch 12/14 removes the call to spider_net_enable_rxchtails() in
spider_net_alloc_rx_skbs(), and nothing else.

So as far as I can tell you should just drop 10/14 and 12/14. 

My worry is that amongst all that rearranging of code, it's not clear
what the semantic change is. Admittedly I don't know the driver that
well, but that's kind of the point - if you and Jim get moved onto a new
project, someone needs to be able to pick up the driver and maintain it.

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

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