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Date: Fri, 28 Mar 2008 21:15:32 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Jack Steiner <steiner@sgi.com>
Cc: tglx@linutronix.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 8/8] x86_64: Support for new UV apic
Message-ID: <20080328201532.GB26555@elte.hu>
References: <20080328191216.GA16455@sgi.com>
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* Jack Steiner <steiner@sgi.com> wrote:

> Index: linux/arch/x86/kernel/apic_64.c
> ===================================================================
> --- linux.orig/arch/x86/kernel/apic_64.c	2008-03-28 13:00:22.000000000 -0500
> +++ linux/arch/x86/kernel/apic_64.c	2008-03-28 13:06:12.000000000 -0500
> @@ -738,6 +738,7 @@ void __cpuinit setup_local_APIC(void)
>  	unsigned int value;
>  	int i, j;
>  
> +	preempt_disable();
>  	value = apic_read(APIC_LVR);
>  
>  	BUILD_BUG_ON((SPURIOUS_APIC_VECTOR & 0x0f) != 0x0f);
> @@ -831,6 +832,7 @@ void __cpuinit setup_local_APIC(void)
>  	else
>  		value = APIC_DM_NMI | APIC_LVT_MASKED;
>  	apic_write(APIC_LVT1, value);
> +	preempt_enable();
>  }

hm, this looks a bit weird - why are all the preempt-disable/enable 
calls needed?

	Ingo