From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756177Ab0IRTKy (ORCPT ); Sat, 18 Sep 2010 15:10:54 -0400 Received: from kroah.org ([198.145.64.141]:51789 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756079Ab0IRTCS (ORCPT ); Sat, 18 Sep 2010 15:02:18 -0400 X-Mailbox-Line: From gregkh@clark.site Sat Sep 18 12:00:01 2010 Message-Id: <20100918190001.553535929@clark.site> User-Agent: quilt/0.48-11.2 Date: Sat, 18 Sep 2010 11:59:06 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Ingo Molnar , Peter Zijlstra , Greg KH , Mike Galbraith Subject: [102/123] sched: Fix rq->clock synchronization when migrating tasks References: <20100918185724.290702750@clark.site> Content-Disposition: inline; filename=sched-fix-rq-clock-synchronization-when-migrating-tasks.patch In-Reply-To: <20100918190024.GA14388@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra commit 861d034ee814917a83bd5de4b26e3b8336ddeeb8 upstream 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 Signed-off-by: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- kernel/sched_fair.c | 2 ++ 1 file changed, 2 insertions(+) --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1963,6 +1963,8 @@ static void task_fork_fair(struct task_s spin_lock_irqsave(&rq->lock, flags); + update_rq_clock(rq); + if (unlikely(task_cpu(p) != this_cpu)) __set_task_cpu(p, this_cpu);