linux-kernel - Re: [PATCH] net/packet: remove dead code and unneeded variable from prb_setup_retire_blk

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Message-ID: <alpine.LNX.2.00.1111150046350.9919@swampdragon.chaosbits.net>
Date:	Tue, 15 Nov 2011 00:48:43 +0100 (CET)
From:	Jesper Juhl <jj@...osbits.net>
To:	Ryan Mallon <rmallon@...il.com>
cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Changli Gao <xiaosuo@...il.com>,
	Ben Greear <greearb@...delatech.com>,
	Chetan Loke <loke.chetan@...il.com>,
	waltje@...lt.NL.Mugnet.ORG, gw4pts@...pts.ampr.org,
	waltje@...ux.com, ross.biro@...il.com, alan@...ux.intel.com
Subject: Re: [PATCH] net/packet: remove dead code and unneeded variable from
 prb_setup_retire_blk_timer()

On Tue, 15 Nov 2011, Ryan Mallon wrote:

> On 15/11/11 10:37, Jesper Juhl wrote:
> 
> > On Mon, 14 Nov 2011, Ryan Mallon wrote:
> > 
> >> On 14/11/11 08:55, Jesper Juhl wrote:
> >>
> >>> We test for 'tx_ring' being != zero and BUG() if that's the case. So after
> >>> that check there is no way that 'tx_ring' could be anything _but_ zero, so
> >>> testing it again is just dead code. Once that dead code is removed, the
> >>> 'pkc' local variable becomes entirely redundant, so remove that as well.
> >>
> >>
> >> What if CONFIG_BUG=n?
> >>
> > 
> > Arrgh, I didn't consider that (should have, but didn't).. In that case 
> > we'll have 
> > #define BUG() do {} while(0)
> > which is not going to work all that peachy with my change...
> > 
> > David: You may want to pass on this one. I obviously didn't think it 
> > through properly - sorry :-(
> > 
> 
> 
> It's something I've never been entirely clear on. How are you meant to
> handle something which really is a fatal bug if CONFIG_BUG=n?
> 
> I think there are several places in the kernel where the expectation is
> that BUG() causes a panic that probably don't behave nicely at all
> (though I guess that might be the expected behaviour) if CONFIG_BUG=n.
> 
You have a point. Perhaps the proper solution would be to remove 
CONFIG_BUG so that it is always enabled...?  As you say, if something is a 
fatal bug there is no sane way to continue, so why do we even allow 
people/systems to try???
That way lies madness it would seem...


-- 
Jesper Juhl <jj@...osbits.net>       http://www.chaosbits.net/
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