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: 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

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ac38225e6d098b0eee977c4b74727252ec0654ef..442efe59d188141be3cf91ced7ba6f9a46702301 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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);
        }

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index cb92dc5f56469ed3e3c76f22fea985f125a5dfdb..d3a3b2646ec4fd84282e7113adaebca022ded036 100644 (file)
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -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);