Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Hao Jia <> | Subject | [PATCH v3 1/4] sched/core: Fixed missing rq clock update before calling set_rq_offline() | Date | Mon, 15 May 2023 14:38:45 +0800 |
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This is triggered during cpu offline when CONFIG_CPU_FREQ is enabled and cpufreq is set to powersave: ------------[ cut here ]------------ rq->clock_update_flags < RQCF_ACT_SKIP WARNING: CPU: 24 PID: 754 at kernel/sched/sched.h:1496 enqueue_top_rt_rq+0x139/0x160 Call Trace: <TASK> ? 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
More detailed key function call graph: rq_offline_rt() __disable_runtime() sched_rt_rq_enqueue() enqueue_top_rt_rq() cpufreq_update_util() <-- depends on CONFIG_CPU_FREQ data->func(data, *rq_clock(rq)*, flags) intel_pstate_update_util() <-- powersave policy callback function
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 <jiahao.os@bytedance.com> --- 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); -- 2.37.0
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