Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753120AbWLOSTN (ORCPT ); Fri, 15 Dec 2006 13:19:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753124AbWLOSTN (ORCPT ); Fri, 15 Dec 2006 13:19:13 -0500 Received: from 216-99-217-87.dsl.aracnet.com ([216.99.217.87]:45707 "EHLO sous-sol.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753120AbWLOSTM (ORCPT ); Fri, 15 Dec 2006 13:19:12 -0500 Date: Fri, 15 Dec 2006 10:20:39 -0800 From: Chris Wright To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: akpm@osdl.org, "Theodore Ts'o" , Zwane Mwaikambo , Justin Forbes , torvalds@osdl.org, Chris Wedgwood , Randy Dunlap , Michael Krufky , Dave Jones , Chuck Wolber , alan@lxorguk.ukuu.org.uk, Arjan van de Ven , Andi Kleen Subject: [patch 25/24] x86-64: Mark rdtsc as sync only for netburst, not for core2 Message-ID: <20061215182039.GG10475@sequoia.sous-sol.org> References: <20061215013337.823935000@sous-sol.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061215013337.823935000@sous-sol.org> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1984 Lines: 47 2.6.18-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 [chrisw: backported to 2.6.18] Signed-off-by: Chris Wright --- Commit: f3d73707a1e84f0687a05144b70b660441e999c7 Author: Arjan van de Ven Date: Thu Dec 7 02:14:12 2006 +0100 arch/x86_64/kernel/setup.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- linux-2.6.18.5.orig/arch/x86_64/kernel/setup.c +++ linux-2.6.18.5/arch/x86_64/kernel/setup.c @@ -1010,7 +1010,10 @@ static void __cpuinit init_intel(struct if ((c->x86 == 0xf && c->x86_model >= 0x03) || (c->x86 == 0x6 && c->x86_model >= 0x0e)) set_bit(X86_FEATURE_CONSTANT_TSC, &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/