From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753239Ab0IFGxF (ORCPT ); Mon, 6 Sep 2010 02:53:05 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:51328 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752441Ab0IFGxE (ORCPT ); Mon, 6 Sep 2010 02:53:04 -0400 Date: Mon, 6 Sep 2010 08:52:29 +0200 From: Ingo Molnar To: Jack Daniel Cc: Peter Zijlstra , LKML , Mike Galbraith , pjohn@mvista.com Subject: Re: clock drift in set_task_cpu() Message-ID: <20100906065229.GA14609@elte.hu> References: <1281002322.1923.1708.camel@laptop> <1281365803.5390.2.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jack Daniel wrote: > Hi Ingo, > > [...] > > Any chance that you will be pulling in this fix ? It's already upstream, as of v2.6.36-rc3. See the commit notification email below from Aug 19. Thanks, Ingo ----- Forwarded message from tip-bot for Peter Zijlstra ----- Date: Fri, 20 Aug 2010 14:16:14 GMT From: tip-bot for Peter Zijlstra To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, peterz@infradead.org, pjohn@mvista.com, wanders.thirst@gmail.com, tglx@linutronix.de, mingo@elte.hu Subject: [tip:sched/urgent] sched: Fix rq->clock synchronization when migrating tasks Commit-ID: 861d034ee814917a83bd5de4b26e3b8336ddeeb8 Gitweb: http://git.kernel.org/tip/861d034ee814917a83bd5de4b26e3b8336ddeeb8 Author: Peter Zijlstra AuthorDate: Thu, 19 Aug 2010 13:31:43 +0200 Committer: Ingo Molnar CommitDate: Fri, 20 Aug 2010 14:59:01 +0200 sched: Fix rq->clock synchronization when migrating tasks sched_fork() -- we do task placement in ->task_fork_fair() ensure we update_rq_clock() so we work with current time. We leave the vruntime in relative state, so the time delay until wake_up_new_task() doesn't matter. wake_up_new_task() -- Since task_fork_fair() left p->vruntime in relative state we can safely migrate, the activate_task() on the remote rq will call update_rq_clock() and causes the clock to be synced (enough). Tested-by: Jack Daniel Tested-by: Philby John Signed-off-by: Peter Zijlstra LKML-Reference: <1281002322.1923.1708.camel@laptop> Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 806d1b2..ab661eb 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -3752,6 +3752,8 @@ static void task_fork_fair(struct task_struct *p) raw_spin_lock_irqsave(&rq->lock, flags); + update_rq_clock(rq); + if (unlikely(task_cpu(p) != this_cpu)) __set_task_cpu(p, this_cpu); ----- End forwarded message -----