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intel_pstate_update_util+0x3b0/0x3b0 rq_offline_rt+0x1b7/0x250 set_rq_offline.part.120+0x28/0x60 rq_attach_root+0xc4/0xd0 cpu_attach_domain+0x3dc/0x7f0 ? __schedule+0x65e/0x1310 partition_sched_domains_locked+0x2a5/0x3c0 rebuild_sched_domains_locked+0x477/0x830 ? percpu_rwsem_wait+0x140/0x140 rebuild_sched_domains+0x1b/0x30 cpuset_hotplug_workfn+0x2ca/0xc90 ? balance_push+0x56/0x120 ? _raw_spin_unlock+0x15/0x30 ? finish_task_switch+0x98/0x2f0 ? __switch_to+0x116/0x410 ? __schedule+0x65e/0x1310 ? internal_add_timer+0x42/0x60 ? _raw_spin_unlock_irqrestore+0x23/0x40 ? add_timer_on+0xd5/0x130 process_one_work+0x1bc/0x3d0 worker_thread+0x4c/0x380 ? preempt_count_add+0x56/0xa0 ? rescuer_thread+0x310/0x310 kthread+0xe6/0x110 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x1f/0x30 Before calling set_rq_offline() we need to update the rq clock to avoid using the old rq clock, and use rq_lock_irqsave()/rq_unlock_irqrestore() to replace raw_spin_rq_lock_irqsave()/raw_spin_rq_unlock_irqrestore() to ensure that rq->clock_update_flags are cleared before updating the rq clock. Steps to reproduce: 1. Enable CONFIG_SMP and CONFIG_CPU_FREQ when compiling the kernel 2. echo 1 > /sys/kernel/debug/clear_warn_once 3. cpupower -c all frequency-set -g powersave 4. Run some rt tasks e.g. Create 5*n rt (100% running) tasks (on a system with n CPUs) 5. Offline cpu one by one until the warninng is triggered Signed-off-by: Hao Jia --- kernel/sched/topology.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 6682535e37c8..b89497696880 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -487,15 +487,17 @@ static void free_rootdomain(struct rcu_head *rcu) void rq_attach_root(struct rq *rq, struct root_domain *rd) { struct root_domain *old_rd = NULL; - unsigned long flags; + struct rq_flags rf; - raw_spin_rq_lock_irqsave(rq, flags); + rq_lock_irqsave(rq, &rf); if (rq->rd) { old_rd = rq->rd; - if (cpumask_test_cpu(rq->cpu, old_rd->online)) + if (cpumask_test_cpu(rq->cpu, old_rd->online)) { + update_rq_clock(rq); set_rq_offline(rq); + } cpumask_clear_cpu(rq->cpu, old_rd->span); @@ -515,7 +517,7 @@ void rq_attach_root(struct rq *rq, struct root_domain *rd) if (cpumask_test_cpu(rq->cpu, cpu_active_mask)) set_rq_online(rq); - raw_spin_rq_unlock_irqrestore(rq, flags); + rq_unlock_irqrestore(rq, &rf); if (old_rd) call_rcu(&old_rd->rcu, free_rootdomain); From patchwork Wed May 10 08:34:50 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Jia X-Patchwork-Id: 91955 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:b0ea:0:b0:3b6:4342:cba0 with SMTP id b10csp3460494vqo; Wed, 10 May 2023 01:41:00 -0700 (PDT) X-Google-Smtp-Source: ACHHUZ5Vj7elwCDtV/pNX0I9Uey+4xKa9XTJCQEEVBtKoIRuJDIF2MOWvO1GeWzAm5BI7a+JIoOa X-Received: by 2002:a17:903:11cd:b0:1ac:63ac:10a7 with SMTP id q13-20020a17090311cd00b001ac63ac10a7mr13982544plh.68.1683708059982; Wed, 10 May 2023 01:40:59 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1683708059; cv=none; d=google.com; s=arc-20160816; b=tWFOgE8A652WAYV2TT93zB2frEHARUHfMyxJDEM6kBcKDpITbwkS/17Jz2W7z+Ozui YA9kgrbtnFxd8nYTBf1JH4+0YsHAt7RNAiIDzkTnLJxT33Jbl5FyKgztgPSL6VnM6exz r8fWSi07Wt8SD5J8WztYy11PSQ2Mj+GhREW9ve65D9L+HJcZx4oQwWK1cTvp/kwRM/Fv S3AJFwRT6uARQTRcY5G6lPCszENWkpGfJ6UOb0KLF3OzjU9ygIxLKbnjVsqztSntzyND stGjcKaQ6W2Wo7jWVZ+1nZ1zRFNSJ1n/dQiNrY2Ep9qtb+bOUdJ5APGd78bJwQuj3OQM JZYA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=J9KFKim9W01aJymh56M6VmTxV6CKXPMr8i9NknkamPs=; b=E7Jo1O7ygKMtjZBfPwsJkF9cXqp3w1DVfiKwX/P/4oucksAnYSQxSE4qadIDkWXRTX U9UVsBODQfcu+Q7NUM9FsEagA9mIEHLdvEOucgkRlVdytd2RgYRvK276E9plBHvPfuwO VMBRnQTnHBXjm3eIMJChXqo/9x2B+IBdIwOyZG91nHvTlnFvtO6xfPUtkJoUnXgVuBmy Qolpr6A+6R+4zKztLZq6zGNJ+wbR16w1folWDKjWQ5ocvKH6JGWo2Kng01ihtTVIYwUR x7eRWHbKY6ykxxecNhYtDsXbj5ClM+kgnbZTWhVWvR1wLEO9G3M58SA5hT9uu7mTpklc 2HlA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@bytedance.com header.s=google header.b=CRFPSzqn; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=bytedance.com Received: from out1.vger.email (out1.vger.email. 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migration_cpu_stop+0x2a0/0x2a0 cpu_stopper_thread+0xa3/0x140 smpboot_thread_fn+0x14f/0x210 ? sort_range+0x20/0x20 kthread+0xe6/0x110 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x1f/0x30 ------------[ cut here ]------------ rq->clock_update_flags & RQCF_UPDATED WARNING: CPU: 54 PID: 0 at kernel/sched/core.c:741 update_rq_clock+0xaf/0x180 Call Trace: unthrottle_cfs_rq+0x4b/0x300 __cfsb_csd_unthrottle+0xe0/0x100 __flush_smp_call_function_queue+0xaf/0x1d0 flush_smp_call_function_queue+0x49/0x90 do_idle+0x17c/0x270 cpu_startup_entry+0x19/0x20 start_secondary+0xfa/0x120 secondary_startup_64_no_verify+0xce/0xdb ------------[ cut here ]------------ rq->clock_update_flags & RQCF_UPDATED WARNING: CPU: 0 PID: 3323 at kernel/sched/core.c:741 update_rq_clock+0xaf/0x180 Call Trace: unthrottle_cfs_rq+0x4b/0x300 rq_offline_fair+0x89/0x90 set_rq_offline.part.118+0x28/0x60 rq_attach_root+0xc4/0xd0 cpu_attach_domain+0x3dc/0x7f0 partition_sched_domains_locked+0x2a5/0x3c0 rebuild_sched_domains_locked+0x477/0x830 rebuild_sched_domains+0x1b/0x30 cpuset_hotplug_workfn+0x2ca/0xc90 ? balance_push+0x56/0xf0 ? _raw_spin_unlock+0x15/0x30 ? finish_task_switch+0x98/0x2f0 ? __switch_to+0x291/0x410 ? __schedule+0x65e/0x1310 process_one_work+0x1bc/0x3d0 worker_thread+0x4c/0x380 ? preempt_count_add+0x92/0xa0 ? rescuer_thread+0x310/0x310 kthread+0xe6/0x110 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x1f/0x30 For the __balance_push_cpu_stop() case, we remove update_rq_clock() from the __migrate_task() function to avoid double updating the rq clock. And in order to avoid missing rq clock update, add update_rq_clock() call before migration_cpu_stop() calls __migrate_task(). For the unthrottle_cfs_rq() case, we use rq_clock_start_loop_update() to prevent multiple calls to update_rq_clock() in unthrottle_cfs_rq(). Note that the rq clock has been updated before the set_rq_offline() function runs, so we don't need to call update_rq_clock() in unthrottle_offline_cfs_rqs(). Suggested-by: Vincent Guittot Signed-off-by: Hao Jia --- kernel/sched/core.c | 7 ++++--- kernel/sched/fair.c | 16 ++++++++++++++++ kernel/sched/sched.h | 21 +++++++++++++++++++++ 3 files changed, 41 insertions(+), 3 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 944c3ae39861..2bcf6a8e71fc 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2398,7 +2398,6 @@ static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf, if (!is_cpu_allowed(p, dest_cpu)) return rq; - update_rq_clock(rq); rq = move_queued_task(rq, rf, p, dest_cpu); return rq; @@ -2456,10 +2455,12 @@ static int migration_cpu_stop(void *data) goto out; } - if (task_on_rq_queued(p)) + if (task_on_rq_queued(p)) { + update_rq_clock(rq); rq = __migrate_task(rq, &rf, p, arg->dest_cpu); - else + } else { p->wake_cpu = arg->dest_cpu; + } /* * XXX __migrate_task() can fail, at which point we might end diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 373ff5f55884..9ec7bde620ff 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5575,6 +5575,13 @@ static void __cfsb_csd_unthrottle(void *arg) struct rq_flags rf; rq_lock(rq, &rf); + /* + * Iterating over the list can trigger several call to + * update_rq_clock() in unthrottle_cfs_rq(). + * Do it once and skip the potential next ones. + */ + update_rq_clock(rq); + rq_clock_start_loop_update(rq); /* * Since we hold rq lock we're safe from concurrent manipulation of @@ -5595,6 +5602,7 @@ static void __cfsb_csd_unthrottle(void *arg) rcu_read_unlock(); + rq_clock_stop_loop_update(rq); rq_unlock(rq, &rf); } @@ -6114,6 +6122,12 @@ static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) struct task_group *tg; lockdep_assert_rq_held(rq); + /* + * The rq clock has already been updated before the + * set_rq_offline() runs, so we should skip updating + * the rq clock again in unthrottle_cfs_rq(). + */ + rq_clock_start_loop_update(rq); rcu_read_lock(); list_for_each_entry_rcu(tg, &task_groups, list) { @@ -6137,6 +6151,8 @@ static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) unthrottle_cfs_rq(cfs_rq); } rcu_read_unlock(); + + rq_clock_stop_loop_update(rq); } #else /* CONFIG_CFS_BANDWIDTH */ diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index ec7b3e0a2b20..9c712f29e5a4 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1536,6 +1536,27 @@ static inline void rq_clock_skip_update(struct rq *rq) rq->clock_update_flags |= RQCF_REQ_SKIP; } +/* + * During cpu offlining and rq wide unthrottling, we can trigger + * an update_rq_clock() for several cfs and rt runqueues (Typically + * when using list_for_each_entry_*) + * rq_clock_start_loop_update() can be called after updating the clock + * once and before iterating over the list to prevent multiple update. + * After the iterative traversal, we need to call rq_clock_stop_loop_update() + * to restore rq->clock_update_flags. + */ +static inline void rq_clock_start_loop_update(struct rq *rq) +{ + lockdep_assert_rq_held(rq); + rq->clock_update_flags |= RQCF_ACT_SKIP; +} + +static inline void rq_clock_stop_loop_update(struct rq *rq) +{ + lockdep_assert_rq_held(rq); + rq->clock_update_flags &= ~RQCF_ACT_SKIP; +} + /* * See rt task throttling, which is the only time a skip * request is canceled.