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Date: Sat, 16 Feb 2008 23:36:38 -0800
From: "Yinghai Lu" <yhlu.kernel@gmail.com>
Subject: Re: [PATCH 3/4] x86_64: Fold pda into per cpu area
In-Reply-To: <86802c440802162222k47f5bebbhf42fef0f11ce3243@mail.gmail.com>
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References: <20080201191414.961558000@sgi.com>
	 <20080201191415.450555000@sgi.com> <20080215201640.GA6200@elte.hu>
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To: Ingo Molnar <mingo@elte.hu>
Cc: travis@sgi.com, Andrew Morton <akpm@linux-foundation.org>, Andi Kleen <ak@suse.de>, Thomas Gleixner <tglx@linutronix.de>, Jeremy Fitzhardinge <jeremy@goop.org>, Christoph Lameter <clameter@sgi.com>, Jack Steiner <steiner@sgi.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org
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On Feb 16, 2008 10:22 PM, Yinghai Lu <yhlu.kernel@gmail.com> wrote:
> On Feb 15, 2008 12:16 PM, Ingo Molnar <mingo@elte.hu> wrote:
> >
> > * travis@sgi.com <travis@sgi.com> wrote:
> >
> > >  include/asm-generic/vmlinux.lds.h |    2 +
> > >  include/linux/percpu.h            |    9 ++++-
> >
> > couldnt these two generic bits be done separately (perhaps a preparatory
> > but otherwise NOP patch pushed upstream straight away) to make
> > subsequent patches only touch x86 architecture files?
>
> this patch need to apply to mainline asap.
>
> or you need revert to the patch about include/asm-x86/percpu.h
>
> +#ifdef CONFIG_X86_64
> +#include <linux/compiler.h>
> +
> +/* Same as asm-generic/percpu.h, except that we store the per cpu offset
> +   in the PDA. Longer term the PDA and every per cpu variable
> +   should be just put into a single section and referenced directly
> +   from %gs */
> +
> +#ifdef CONFIG_SMP
> +#include <asm/pda.h>
> +
> +#define __per_cpu_offset(cpu) (cpu_pda(cpu)->data_offset)
> +#define __my_cpu_offset read_pda(data_offset)
> +
> +#define per_cpu_offset(x) (__per_cpu_offset(x))
> +
>  #endif
> +#include <asm-generic/percpu.h>
> +
> +DECLARE_PER_CPU(struct x8664_pda, pda);
> +
> +#else /* CONFIG_X86_64 */
>
> because current tree
> in setup_per_cpu_areas will have
>      cpu_pda(i)->data_offset = ptr - __per_cpu_start;
>
> but at that time all APs will use cpu_pda for boot cpu...,and APs will
> get their pda in do_boot_cpu()

sorry, boot_cpu_pda is array... so that is safe.

YH

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