Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751086AbXAFCZr (ORCPT ); Fri, 5 Jan 2007 21:25:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751089AbXAFCZq (ORCPT ); Fri, 5 Jan 2007 21:25:46 -0500 Received: from 216-99-217-87.dsl.aracnet.com ([216.99.217.87]:47727 "EHLO sous-sol.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751086AbXAFCZm (ORCPT ); Fri, 5 Jan 2007 21:25:42 -0500 Message-Id: <20070106022945.273419000@sous-sol.org> References: <20070106022753.334962000@sous-sol.org> User-Agent: quilt/0.45-1 Date: Fri, 05 Jan 2007 18:27:58 -0800 From: Chris Wright To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , torvalds@osdl.org, akpm@osdl.org, alan@lxorguk.ukuu.org.uk, Arjan van de Ven , Andi Kleen Subject: [patch 05/50] x86-64: Mark rdtsc as sync only for netburst, not for core2 Content-Disposition: inline; filename=x86-64-mark-rdtsc-as-sync-only-for-netburst-not-for-core2.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1922 Lines: 48 -stable review patch. If anyone has any objections, please let us know. ------------------ From: Arjan van de Ven On the Core2 cpus, the rdtsc instruction is not serializing (as defined in the architecture reference since rdtsc exists) and due to the deep speculation of these cores, it's possible that you can observe time go backwards between cores due to this speculation. Since the kernel already deals with this with the SYNC_RDTSC flag, the solution is simple, only assume that the instruction is serializing on family 15... The price one pays for this is a slightly slower gettimeofday (by a dozen or two cycles), but that increase is quite small to pay for a really-going-forward tsc counter. Signed-off-by: Arjan van de Ven Signed-off-by: Andi Kleen Signed-off-by: Chris Wright --- Commit: f3d73707a1e84f0687a05144b70b660441e999c7 Author: Arjan van de Ven AuthorDate: Thu Dec 7 02:14:12 2006 +0100 arch/x86_64/kernel/setup.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- linux-2.6.19.1.orig/arch/x86_64/kernel/setup.c +++ linux-2.6.19.1/arch/x86_64/kernel/setup.c @@ -854,7 +854,10 @@ 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); - set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability); + if (c->x86 == 15) + set_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability); + else + clear_bit(X86_FEATURE_SYNC_RDTSC, &c->x86_capability); c->x86_max_cores = intel_num_cpu_cores(c); srat_detect_node(); -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/