From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752861Ab0CBMk1 (ORCPT ); Tue, 2 Mar 2010 07:40:27 -0500 Received: from hera.kernel.org ([140.211.167.34]:48584 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751487Ab0CBMk0 (ORCPT ); Tue, 2 Mar 2010 07:40:26 -0500 Date: Tue, 2 Mar 2010 12:39:34 GMT From: tip-bot for Dimitri Sivanich Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, venkatesh.pallipadi@intel.com, tglx@linutronix.de, sivanich@sgi.com, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, venkatesh.pallipadi@intel.com, tglx@linutronix.de, sivanich@sgi.com, mingo@elte.hu In-Reply-To: <20100301174815.GC8224@sgi.com> References: <20100301174815.GC8224@sgi.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] x86: Fix sched_clock_cpu for systems with unsynchronized TSC Message-ID: Git-Commit-ID: 14be1f7454ea96ee614467a49cf018a1a383b189 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Tue, 02 Mar 2010 12:39:36 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 14be1f7454ea96ee614467a49cf018a1a383b189 Gitweb: http://git.kernel.org/tip/14be1f7454ea96ee614467a49cf018a1a383b189 Author: Dimitri Sivanich AuthorDate: Mon, 1 Mar 2010 11:48:15 -0600 Committer: Ingo Molnar CommitDate: Tue, 2 Mar 2010 13:36:11 +0100 x86: Fix sched_clock_cpu for systems with unsynchronized TSC On UV systems, the TSC is not synchronized across blades. The sched_clock_cpu() function is returning values that can go backwards (I've seen as much as 8 seconds) when switching between cpus. As each cpu comes up, early_init_intel() will currently set the sched_clock_stable flag true. When mark_tsc_unstable() runs, it clears the flag, but this only occurs once (the first time a cpu comes up whose TSC is not synchronized with cpu 0). After this, early_init_intel() will set the flag again as the next cpu comes up. Only set sched_clock_stable if tsc has not been marked unstable. Signed-off-by: Dimitri Sivanich Acked-by: Venkatesh Pallipadi Acked-by: Peter Zijlstra LKML-Reference: <20100301174815.GC8224@sgi.com> Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/intel.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 879666f..7e1cca1 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -70,7 +70,8 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) if (c->x86_power & (1 << 8)) { set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC); set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC); - sched_clock_stable = 1; + if (!check_tsc_unstable()) + sched_clock_stable = 1; } /*