linux-kernel - [tip: sched/core] sched/core: Fixed missing rq clock update before calling set_rq

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Date:   Mon, 19 Jun 2023 11:04:51 -0000
From:   "tip-bot2 for Hao Jia" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Ben Segall <bsegall@...gle.com>, Hao Jia <jiahao.os@...edance.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/core: Fixed missing rq clock update before
 calling set_rq_offline()

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     cab3ecaed5cdcc9c36a96874b4c45056a46ece45
Gitweb:        https://git.kernel.org/tip/cab3ecaed5cdcc9c36a96874b4c45056a46ece45
Author:        Hao Jia <jiahao.os@...edance.com>
AuthorDate:    Tue, 13 Jun 2023 16:20:09 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Fri, 16 Jun 2023 22:08:12 +02:00

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@...gle.com>
Signed-off-by: Hao Jia <jiahao.os@...edance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>
Link: https://lkml.kernel.org/r/20230613082012.49615-2-jiahao.os@bytedance.com
---
 kernel/sched/core.c     | 2 +-
 kernel/sched/topology.c | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ac38225..442efe5 100644
--- 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 cb92dc5..d3a3b26 100644
--- 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);