linux-kernel - Re: [PATCH v4 6/7] x86/i387.c: Thread xstate is initialized only on BSP once

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Date:	Sun, 13 Nov 2011 10:17:21 -0500
From:	Brian Gerst <brgerst@...il.com>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	H Peter Anvin <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tony Luck <tony.luck@...el.com>,
	Arjan van de Ven <arjan.van.de.ven@...el.com>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Len Brown <len.brown@...el.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v4 6/7] x86/i387.c: Thread xstate is initialized only on
 BSP once

On Sat, Nov 12, 2011 at 12:26 AM, Fenghua Yu <fenghua.yu@...el.com> wrote:
> From: Fenghua Yu <fenghua.yu@...el.com>
>
> init_thread_xstate() is only called on BSP once to avoid overriding xstate_size.
>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> ---
>  arch/x86/kernel/i387.c |    9 ++++++++-
>  1 files changed, 8 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
> index 739d859..72652ff 100644
> --- a/arch/x86/kernel/i387.c
> +++ b/arch/x86/kernel/i387.c
> @@ -93,6 +93,7 @@ void __cpuinit fpu_init(void)
>  {
>        unsigned long cr0;
>        unsigned long cr4_mask = 0;
> +       static int once = 1;
>
>        if (cpu_has_fxsr)
>                cr4_mask |= X86_CR4_OSFXSR;
> @@ -107,8 +108,14 @@ void __cpuinit fpu_init(void)
>                cr0 |= X86_CR0_EM;
>        write_cr0(cr0);
>
> -       if (!smp_processor_id())
> +       /*
> +        * init_thread_xstate is only called on BSP once to avoid overriding
> +        * xstate_size.
> +        */
> +       if (!smp_processor_id() && once) {
> +               once = 0;
>                init_thread_xstate();
> +       }

Just check if xstate_size is 0 instead of adding a new flag.

--
Brian Gerst
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