Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755317AbaFYITt (ORCPT ); Wed, 25 Jun 2014 04:19:49 -0400 Received: from relay.parallels.com ([195.214.232.42]:35626 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754602AbaFYITp (ORCPT ); Wed, 25 Jun 2014 04:19:45 -0400 Message-ID: <1403684382.3462.42.camel@tkhai> Subject: [PATCH v3 1/3] sched/fair: Disable runtime_enabled on dying rq From: Kirill Tkhai To: CC: Peter Zijlstra , Ingo Molnar , , Srikar Dronamraju , "Mike Galbraith" , , Ben Segall , Paul Turner Date: Wed, 25 Jun 2014 12:19:42 +0400 In-Reply-To: <20140625081502.2861.12526.stgit@tkhai> References: <20140625081502.2861.12526.stgit@tkhai> Organization: Parallels Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5-2+b3 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.30.26.172] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We kill rq->rd on the CPU_DOWN_PREPARE stage: cpuset_cpu_inactive -> cpuset_update_active_cpus -> partition_sched_domains -> -> cpu_attach_domain -> rq_attach_root -> set_rq_offline This unthrottles all throttled cfs_rqs. But the cpu is still able to call schedule() till take_cpu_down->__cpu_disable() is called from stop_machine. This case the tasks from just unthrottled cfs_rqs are pickable in a standard scheduler way, and they are picked by dying cpu. The cfs_rqs becomes throttled again, and migrate_tasks() in migration_call skips their tasks (one more unthrottle in migrate_tasks()->CPU_DYING does not happen, because rq->rd is already NULL). Patch sets runtime_enabled to zero. This guarantees, the runtime is not accounted, and the cfs_rqs won't exceed given cfs_rq->runtime_remaining = 1, and tasks will be pickable in migrate_tasks(). runtime_enabled is recalculated again when rq becomes online again. Ben Segall also noticed, we always enable runtime in tg_set_cfs_bandwidth(). Actually, we should do that for online cpus only. To prevent races with unthrottle_offline_cfs_rqs() we take get_online_cpus() lock. v2: Fix race with tg_set_cfs_bandwidth(). Move cfs_rq->runtime_enabled=0 above unthrottle_cfs_rq(). v3: {get,put}_online_cpus() Signed-off-by: Kirill Tkhai CC: Konstantin Khorenko CC: Ben Segall CC: Paul Turner CC: Srikar Dronamraju CC: Mike Galbraith CC: Peter Zijlstra CC: Ingo Molnar --- kernel/sched/core.c | 8 +++++++- kernel/sched/fair.c | 22 ++++++++++++++++++++++ 2 files changed, 29 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ceea8d0..d9c4a08 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7807,6 +7807,11 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) if (period > max_cfs_quota_period) return -EINVAL; + /* + * Prevent race between setting of cfs_rq->runtime_enabled and + * unthrottle_offline_cfs_rqs(). + */ + get_online_cpus(); mutex_lock(&cfs_constraints_mutex); ret = __cfs_schedulable(tg, period, quota); if (ret) @@ -7832,7 +7837,7 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) } raw_spin_unlock_irq(&cfs_b->lock); - for_each_possible_cpu(i) { + for_each_online_cpu(i) { struct cfs_rq *cfs_rq = tg->cfs_rq[i]; struct rq *rq = cfs_rq->rq; @@ -7848,6 +7853,7 @@ static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota) cfs_bandwidth_usage_dec(); out_unlock: mutex_unlock(&cfs_constraints_mutex); + put_online_cpus(); return ret; } diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1f9c457..5616d23 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3776,6 +3776,19 @@ static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) hrtimer_cancel(&cfs_b->slack_timer); } +static void __maybe_unused update_runtime_enabled(struct rq *rq) +{ + struct cfs_rq *cfs_rq; + + for_each_leaf_cfs_rq(rq, cfs_rq) { + struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth; + + raw_spin_lock(&cfs_b->lock); + cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF; + raw_spin_unlock(&cfs_b->lock); + } +} + static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) { struct cfs_rq *cfs_rq; @@ -3789,6 +3802,12 @@ static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) * there's some valid quota amount */ cfs_rq->runtime_remaining = 1; + /* + * Offline rq is schedulable till cpu is completely disabled + * in take_cpu_down(), so we prevent new cfs throttling here. + */ + cfs_rq->runtime_enabled = 0; + if (cfs_rq_throttled(cfs_rq)) unthrottle_cfs_rq(cfs_rq); } @@ -3832,6 +3851,7 @@ static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) return NULL; } static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} +static inline void update_runtime_enabled(struct rq *rq) {} static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {} #endif /* CONFIG_CFS_BANDWIDTH */ @@ -7325,6 +7345,8 @@ void trigger_load_balance(struct rq *rq) static void rq_online_fair(struct rq *rq) { update_sysctl(); + + update_runtime_enabled(rq); } static void rq_offline_fair(struct rq *rq) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/