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

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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: Ben Segall <bsegall@google.com>
Signed-off-by: Hao Jia <jiahao.os@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lkml.kernel.org/r/20230613082012.49615-2-jiahao.os@bytedance.com
This commit is contained in:
Hao Jia 2023-06-13 16:20:09 +08:00 • committed by Peter Zijlstra
parent e20f204c88
commit cab3ecaed5
2 changed files with 4 additions and 4 deletions
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2
kernel/sched/core.c
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@ -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);
}

6
kernel/sched/topology.c
View file

@ -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);