From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751401AbaFEKuD (ORCPT ); Thu, 5 Jun 2014 06:50:03 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:35439 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750939AbaFEKuC (ORCPT ); Thu, 5 Jun 2014 06:50:02 -0400 X-IronPort-AV: E=Sophos;i="4.98,980,1392134400"; d="scan'208";a="31505593" Message-ID: <53904C6B.90001@cn.fujitsu.com> Date: Thu, 5 Jun 2014 18:54:35 +0800 From: Lai Jiangshan User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc14 Thunderbird/3.1.4 MIME-Version: 1.0 To: Peter Zijlstra CC: , Sasha Levin , Tejun Heo , LKML , Dave Jones , Ingo Molnar , Thomas Gleixner , Steven Rostedt Subject: Re: workqueue: WARN at at kernel/workqueue.c:2176 References: <20140516162945.GZ11096@twins.programming.kicks-ass.net> <53849EB7.9090302@linux.vnet.ibm.com> <20140527142637.GB19143@laptop.programming.kicks-ass.net> <53875F09.3090607@linux.vnet.ibm.com> <538DB076.4090704@cn.fujitsu.com> <20140603141659.GO30445@twins.programming.kicks-ass.net> <538E840D.2040300@cn.fujitsu.com> <20140604064946.GF30445@twins.programming.kicks-ass.net> <538ED7EB.5050303@cn.fujitsu.com> <20140604093907.GC11096@twins.programming.kicks-ass.net> In-Reply-To: <20140604093907.GC11096@twins.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.226.103] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The patch is not tested by Jason, I don't know whether the patch fix the problem. The changlog including the "Reported-by:" and "Tested-by:" need to be updated after it is proved. ------------ Subject: [PATCH] sched: migrate the waking tasks Current code skips to migrate the waking task silently when TTWU_QUEUE is enabled. When a task is waking, it is pending on the wake_list of the rq, but it is not on queue (task->on_rq == 0). In this case, set_cpus_allowed_ptr() and __migrate_task() will not migrate it due to it is not on queue. This behavior is incorrect, because the task had been already waken-up, it will be running on the wrong CPU without correct placement until the next wake-up or update for cpus_allowed. To fix this problem, we need to make the waking tasks on-queue (transfer the waking tasks to running state) before migrate them. Signed-off-by: Lai Jiangshan --- diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 268a45e..d05a5a1 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1474,20 +1474,24 @@ static int ttwu_remote(struct task_struct *p, int wake_flags) } #ifdef CONFIG_SMP -static void sched_ttwu_pending(void) +static void sched_ttwu_pending_locked(struct rq *rq) { - struct rq *rq = this_rq(); struct llist_node *llist = llist_del_all(&rq->wake_list); struct task_struct *p; - raw_spin_lock(&rq->lock); - while (llist) { p = llist_entry(llist, struct task_struct, wake_entry); llist = llist_next(llist); ttwu_do_activate(rq, p, 0); } +} +static void sched_ttwu_pending(void) +{ + struct rq *rq = this_rq(); + + raw_spin_lock(&rq->lock); + sched_ttwu_pending_locked(rq); raw_spin_unlock(&rq->lock); } @@ -4530,6 +4534,11 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) goto out; dest_cpu = cpumask_any_and(cpu_active_mask, new_mask); + + /* Ensure it is on rq for migration if it is waking */ + if (p->state == TASK_WAKING) + sched_ttwu_pending_locked(rq); + if (p->on_rq) { struct migration_arg arg = { p, dest_cpu }; /* Need help from migration thread: drop lock and wait. */ @@ -4576,6 +4585,10 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p))) goto fail; + /* Ensure it is on rq for migration if it is waking */ + if (p->state == TASK_WAKING) + sched_ttwu_pending_locked(rq_src); + /* * If we're not on a rq, the next wake-up will ensure we're * placed properly.