linux-kernel - Re: [PATCH 3/4] x86_64: Fold pda into per cpu area

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Date:	Sat, 16 Feb 2008 23:36:38 -0800
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	travis@....com, "Andrew Morton" <akpm@...ux-foundation.org>,
	"Andi Kleen" <ak@...e.de>, "Thomas Gleixner" <tglx@...utronix.de>,
	"Jeremy Fitzhardinge" <jeremy@...p.org>,
	"Christoph Lameter" <clameter@....com>,
	"Jack Steiner" <steiner@....com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] x86_64: Fold pda into per cpu area

On Feb 16, 2008 10:22 PM, Yinghai Lu <yhlu.kernel@...il.com> wrote:
> On Feb 15, 2008 12:16 PM, Ingo Molnar <mingo@...e.hu> wrote:
> >
> > * travis@....com <travis@....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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