Commit cab3ecae authored by Hao Jia's avatar Hao Jia Committed by Peter Zijlstra
Browse files

sched/core: Fixed missing rq clock update before calling set_rq_offline() 



When using a cpufreq governor that uses
cpufreq_add_update_util_hook(), it is possible to trigger a missing
update_rq_clock() warning for the CPU hotplug path:

  rq_attach_root()
    set_rq_offline()
      rq_offline_rt()
	__disable_runtime()
	  sched_rt_rq_enqueue()
	    enqueue_top_rt_rq()
	      cpufreq_update_util()
		data->func(data, rq_clock(rq), flags)

Move update_rq_clock() from sched_cpu_deactivate() (one of it's
callers) into set_rq_offline() such that it covers all
set_rq_offline() usage.

Additionally change rq_attach_root() to use rq_lock_irqsave() so that
it will properly manage the runqueue clock flags.

Suggested-by: default avatarBen Segall <bsegall@google.com>
Signed-off-by: default avatarHao Jia <jiahao.os@bytedance.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20230613082012.49615-2-jiahao.os@bytedance.com
parent e20f204c

kernel/sched/core.c

+1 −1
Original line number Diff line number Diff line
@@ -9585,6 +9585,7 @@ void set_rq_offline(struct rq *rq) 
	if (rq->online) {

		const struct sched_class *class;



		update_rq_clock(rq);

		for_each_class(class) {

			if (class->rq_offline)

				class->rq_offline(rq);
@@ -9726,7 +9727,6 @@ int sched_cpu_deactivate(unsigned int cpu) 


	rq_lock_irqsave(rq, &rf);

	if (rq->rd) {

		update_rq_clock(rq);

		BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));

		set_rq_offline(rq);

	}

kernel/sched/topology.c

+3 −3
Original line number Diff line number Diff line
@@ -487,9 +487,9 @@ 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;
@@ -515,7 +515,7 @@ 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);