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Date: Tue, 27 Aug 2013 15:37:16 +0000
From: Christoph Lameter <cl@linux.com>
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To: Geert Uytterhoeven <geert@linux-m68k.org>
cc: Tejun Heo <tj@kernel.org>, akpm@linuxfoundation.org,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
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        Steven Rostedt <srostedt@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [guv v2 20/31] powerpc: Replace __get_cpu_var uses
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On Tue, 27 Aug 2013, Geert Uytterhoeven wrote:

> On Mon, Aug 26, 2013 at 10:44 PM, Christoph Lameter <cl@linux.com> wrote:
> > __get_cpu_var() is used for multiple purposes in the kernel source. One of them is
> > address calculation via the form &__get_cpu_var(x). This calculates the address for
> > the instance of the percpu variable of the current processor based on an offset.
> >
> > Others usage cases are for storing and retrieving data from the current processors percpu area.
>
> use cases
>
> > __get_cpu_var() always only does a address determination. However, store and retrieve operations
>
> an address
>
> > This patch converts __get_cpu_var into either and explicit address calculation using this_cpu_ptr()
>
> an explicit
>
> > 4. Retrieve the content of a percpu struct
> >
> >         DEFINE_PER_CPU(struct mystruct, y);
> >         struct mystruct x = __get_cpu_var(y);
> >
> >    Converts to
> >
> >         memcpy(this_cpu_ptr(&y), x, sizeof(x));
>
> Let's hope the actual code copies in the other direction ;-)

Ok fixed that as well.