linux-kernel - Re: [patch] Mark rdtsc as sync only for netburst, not for core2

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Message-ID: <456D372C.9080800@linux.intel.com>
Date:	Wed, 29 Nov 2006 08:30:52 +0100
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
CC:	Andi Kleen <ak@...e.de>, linux-kernel@...r.kernel.org,
	akpm@...l.org
Subject: Re: [patch] Mark rdtsc as sync only for netburst, not for core2

Zhang, Yanmin wrote:
> If it's a single processor, the go backwards issue doesn't exist. Below is
> my patch based on Arjan's. It's against 2.6.19-rc5-mm2.
Hi,

this patch is incorrect
> --- linux-2.6.19-rc5-mm2_arjan/arch/x86_64/kernel/setup.c	2006-11-29 10:41:21.000000000 +0800
> +++ linux-2.6.19-rc5-mm2_arjan_fix/arch/x86_64/kernel/setup.c	2006-11-29 10:42:28.000000000 +0800
> @@ -861,7 +861,7 @@ static void __cpuinit init_intel(struct 
>  		set_bit(X86_FEATURE_CONSTANT_TSC, &c->x86_capability);
>  	if (c->x86 == 6)
>  		set_bit(X86_FEATURE_REP_GOOD, &c->x86_capability);
> -	if (c->x86 == 15)
> +	if (c->x86 == 15 && num_possible_cpus() != 1)
>  		set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability);

first of all, you probably meant "|| num_possible_cpus() == 1"

but second of all, the core2 cpus are dual core so.. .what does it 
bring you at all?
-
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