From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932226Ab1LOFoU (ORCPT ); Thu, 15 Dec 2011 00:44:20 -0500 Received: from TYO202.gate.nec.co.jp ([202.32.8.206]:48404 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752152Ab1LOFoQ (ORCPT ); Thu, 15 Dec 2011 00:44:16 -0500 Date: Thu, 15 Dec 2011 14:37:41 +0900 From: Daisuke Nishimura To: LKML , cgroups Cc: Ingo Molnar , Peter Zijlstra , Paul Turner , Daisuke Nishimura Subject: [PATCH 3/3] sched: fix cgroup movement of waking process Message-Id: <20111215143741.df82dd50.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20111215143506.335e443e.nishimura@mxp.nes.nec.co.jp> References: <20111213155710.5b453415.nishimura@mxp.nes.nec.co.jp> <20111215143506.335e443e.nishimura@mxp.nes.nec.co.jp> Organization: NEC Soft, Ltd. X-Mailer: Sylpheed 3.1.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is a small race between try_to_wake_up() and sched_move_task(), which is trying to move the process being woken up. try_to_wake_up() on CPU0 sched_move_task() on CPU1 --------------------------------+--------------------------------- raw_spin_lock_irqsave(p->pi_lock) task_waking_fair() ->p.se.vruntime -= cfs_rq->min_vruntime ttwu_queue() ->send reschedule IPI to CPU1 raw_spin_unlock_irqsave(p->pi_lock) task_rq_lock() -> tring to aquire both p->pi_lock and rq->lock with IRQ disabled task_move_group_fair() -> p.se.vruntime -= (old)cfs_rq->min_vruntime += (new)cfs_rq->min_vruntime task_rq_unlock() (via IPI) sched_ttwu_pending() raw_spin_lock(rq->lock) ttwu_do_activate() ... enqueue_entity() child.se->vruntime += cfs_rq->min_vruntime raw_spin_unlock(rq->lock) As a result, vruntime of the process becomes far bigger than min_vruntime, if (new)cfs_rq->min_vruntime >> (old)cfs_rq->min_vruntime. This patch fixes this problem by just ignoring such process in task_move_group_fair(), because the vruntime has already been normalized in task_waking_fair(). Signed-off-by: Daisuke Nishimura --- kernel/sched/fair.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index b1db01b..afd13a5 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5345,11 +5345,13 @@ static void task_move_group_fair(struct task_struct *p, int on_rq) * * - Moving a forked child which is waiting for being woken up by * wake_up_new_task(). + * - Moving a task which has been woken up by try_to_wake_up() and + * waiting for actually being woken up by sched_ttwu_pending(). * * To prevent boost or penalty in the new cfs_rq caused by delta * min_vruntime between the two cfs_rqs, we skip vruntime adjustment. */ - if (!on_rq && !p->se.sum_exec_runtime) + if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING)) on_rq = 1; if (!on_rq) -- 1.7.1