Date: Wed, 7 Nov 2007 15:44:31 +0900
From: Simon Horman <horms@verge.net.au>
To: David Miller <davem@davemloft.net>
Cc: luming.yu@gmail.com, linux-ia64@vger.kernel.org,
       linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
       Arjan van de Ven <arjan@linux.intel.com>,
       Rusty Russell <rusty@rustcorp.com.au>, Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] fix typo in per_cpu_offset
Message-ID: <20071107064429.GC3571@verge.net.au>
References: <3877989d0710230015x1640388aod98cae2fa3fc82c2@mail.gmail.com> <20071030071513.GE5361@verge.net.au> <20071030.003622.265888160.davem@davemloft.net> <20071030085054.GE10635@verge.net.au>
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On Tue, Oct 30, 2007 at 05:50:56PM +0900, Simon Horman wrote:
> On Tue, Oct 30, 2007 at 12:36:22AM -0700, David Miller wrote:
> > From: Simon Horman <horms@verge.net.au>
> > Date: Tue, 30 Oct 2007 16:15:13 +0900
> > 
> > > Though curiuously with my config nothing uses per_cpu_offset()
> > > (I added a bogus call to produce an error.) Is it actually
> > > used on ia64?
> > 
> > It is unused, and in that regard should probably be deleted.
> > 
> > include/asm-generic/percpu.h defines a seemingly similarly
> > unused per_cpu_offset() macro define as well
> 
> It looks like they were both added by "[PATCH] lockdep: add per_cpu_offset()"
> (a875a69f8b00a38b4f40d9632a4fc71a159f0e0d)
> 
> Perhaps they were used at that time?

I looked into this a little further:

I'm pretty much convinced that the asm-ia64 version of per_cpu_offset()
is unused as ia64 doesn't have lockdep. I will send a patch to get rid
of it. The generic version might be used on mips, sh or arm with
CONFIG_SMP, as these architectures have lockdep. I did managed to
produce a compiler error on mips by removing the asm-generic version of
per_cpu_offset().

-- 
Horms
  H: http://www.vergenet.net/~horms/
  W: http://www.valinux.co.jp/en/

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