From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932079Ab1ABH5t (ORCPT ); Sun, 2 Jan 2011 02:57:49 -0500 Received: from mail.windriver.com ([147.11.1.11]:35295 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753566Ab1ABHXG (ORCPT ); Sun, 2 Jan 2011 02:23:06 -0500 From: Paul Gortmaker To: stable@kernel.org, linux-kernel@vger.kernel.org Cc: stable-review@kernel.org, Peter Zijlstra , Peter Zijlstra , Ingo Molnar , Paul Gortmaker Subject: [34-longterm 091/260] sched: Fix rq->clock synchronization when migrating tasks Date: Sun, 2 Jan 2011 02:16:27 -0500 Message-Id: <1293952756-15010-92-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.3.3 In-Reply-To: <1293952756-15010-1-git-send-email-paul.gortmaker@windriver.com> References: <1293952756-15010-1-git-send-email-paul.gortmaker@windriver.com> X-OriginalArrivalTime: 02 Jan 2011 07:21:50.0024 (UTC) FILETIME=[B8D32480:01CBAA4D] 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: Paul Gortmaker --- 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 684e173..461d312 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -3588,6 +3588,8 @@ 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); -- 1.7.3.3