From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761688AbZE1MTT (ORCPT ); Thu, 28 May 2009 08:19:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757354AbZE1MTE (ORCPT ); Thu, 28 May 2009 08:19:04 -0400 Received: from hera.kernel.org ([140.211.167.34]:59254 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755545AbZE1MTC (ORCPT ); Thu, 28 May 2009 08:19:02 -0400 Date: Thu, 28 May 2009 12:18:35 GMT From: tip-bot for Petr Tesarik To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, stable@kernel.org, ptesarik@suse.cz, tglx@linutronix.de Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, stable@kernel.org, tglx@linutronix.de, ptesarik@suse.cz In-Reply-To: <9d0ea9ea0f866bdc1f4d76831221ae117f11ea67.1243241859.git.ptesarik@suse.cz> References: <9d0ea9ea0f866bdc1f4d76831221ae117f11ea67.1243241859.git.ptesarik@suse.cz> Subject: [tip:x86/vdso] x86: move rdtsc_barrier() into the TSC vread method Message-ID: Git-Commit-ID: 7d96fd41cadc55f4e00231c8c71b8e25c779f122 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-4.0 (hera.kernel.org [127.0.0.1]); Thu, 28 May 2009 12:18:36 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 7d96fd41cadc55f4e00231c8c71b8e25c779f122 Gitweb: http://git.kernel.org/tip/7d96fd41cadc55f4e00231c8c71b8e25c779f122 Author: Petr Tesarik AuthorDate: Mon, 25 May 2009 11:02:02 +0200 Committer: Thomas Gleixner CommitDate: Thu, 28 May 2009 14:15:54 +0200 x86: move rdtsc_barrier() into the TSC vread method The *fence instructions were moved to vsyscall_64.c by commit cb9e35dce94a1b9c59d46224e8a94377d673e204. But this breaks the vDSO, because vread methods are also called from there. Besides, the synchronization might be unnecessary for other time sources than TSC. [ Impact: fix potential time warp in VDSO ] Signed-off-by: Petr Tesarik LKML-Reference: <9d0ea9ea0f866bdc1f4d76831221ae117f11ea67.1243241859.git.ptesarik@suse.cz> Signed-off-by: Thomas Gleixner Cc: --- arch/x86/kernel/tsc.c | 11 ++++++++++- arch/x86/kernel/vsyscall_64.c | 8 -------- 2 files changed, 10 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index d57de05..cf8611d 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -710,7 +710,16 @@ static cycle_t read_tsc(struct clocksource *cs) #ifdef CONFIG_X86_64 static cycle_t __vsyscall_fn vread_tsc(void) { - cycle_t ret = (cycle_t)vget_cycles(); + cycle_t ret; + + /* + * Surround the RDTSC by barriers, to make sure it's not + * speculated to outside the seqlock critical section and + * does not cause time warps: + */ + rdtsc_barrier(); + ret = (cycle_t)vget_cycles(); + rdtsc_barrier(); return ret >= __vsyscall_gtod_data.clock.cycle_last ? ret : __vsyscall_gtod_data.clock.cycle_last; diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index 44153af..25ee06a 100644 --- a/arch/x86/kernel/vsyscall_64.c +++ b/arch/x86/kernel/vsyscall_64.c @@ -132,15 +132,7 @@ static __always_inline void do_vgettimeofday(struct timeval * tv) return; } - /* - * Surround the RDTSC by barriers, to make sure it's not - * speculated to outside the seqlock critical section and - * does not cause time warps: - */ - rdtsc_barrier(); now = vread(); - rdtsc_barrier(); - base = __vsyscall_gtod_data.clock.cycle_last; mask = __vsyscall_gtod_data.clock.mask; mult = __vsyscall_gtod_data.clock.mult;