From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752362AbcHLITS (ORCPT ); Fri, 12 Aug 2016 04:19:18 -0400 Received: from mail-pa0-f67.google.com ([209.85.220.67]:33497 "EHLO mail-pa0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752354AbcHLITI (ORCPT ); Fri, 12 Aug 2016 04:19:08 -0400 From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Wanpeng Li , Ingo Molnar , Peter Zijlstra , Juri Lelli , Luca Abeni , Frederic Weisbecker Subject: [PATCH v2] sched/deadline: Fix the intention to re-evalute tick dependency for offline cpu Date: Fri, 12 Aug 2016 16:19:00 +0800 Message-Id: <1470989940-3886-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li The dl task will be replenished after dl task timer fire and start a new period. It will be enqueued and to re-evaluate its dependency on the tick in order to restart it. However, if cpu is hot-unplug, irq_work_queue will splash since the target cpu is offline. As a result: WARNING: CPU: 2 PID: 0 at kernel/irq_work.c:69 irq_work_queue_on+0xad/0xe0 Call Trace: dump_stack+0x99/0xd0 __warn+0xd1/0xf0 warn_slowpath_null+0x1d/0x20 irq_work_queue_on+0xad/0xe0 tick_nohz_full_kick_cpu+0x44/0x50 tick_nohz_dep_set_cpu+0x74/0xb0 enqueue_task_dl+0x226/0x480 activate_task+0x5c/0xa0 dl_task_timer+0x19b/0x2c0 ? push_dl_task.part.31+0x190/0x190 This can be triggered by hot-unplug the full dynticks cpu which dl task is running on. We enqueue the dl task on the offline CPU, because we need to do replenish for start_dl_timer(). So, as Juri pointed out, we would need to do is calling replenish_dl_entity() directly, instead of enqueue_task_dl(). pi_se shouldn't be a problem as the task shouldn't be boosted if it was throttled. This patch fix it by just replenish dl entity to avoid the intention to re-evaluate tick dependency if the cpu is offline. Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Luca Abeni Cc: Frederic Weisbecker Signed-off-by: Wanpeng Li --- v1 -> v2: * replenish dl entity kernel/sched/deadline.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index d091f4a..b141bd2 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -641,11 +641,15 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) goto unlock; } - enqueue_task_dl(rq, p, ENQUEUE_REPLENISH); - if (dl_task(rq->curr)) - check_preempt_curr_dl(rq, p, 0); - else - resched_curr(rq); + if (unlikely(!rq->online)) + replenish_dl_entity(dl_se, dl_se); + else { + enqueue_task_dl(rq, p, ENQUEUE_REPLENISH); + if (dl_task(rq->curr)) + check_preempt_curr_dl(rq, p, 0); + else + resched_curr(rq); + } #ifdef CONFIG_SMP /* -- 1.9.1