Re: [PATCH v2] rt: cpufreq: Fix cpu hotplug hang

When selecting PREEMPT_RT, cpufreq_driver->stop_cpu(policy) might get
stuck due to irq_work_sync() pending for work on lazy_list, which had
no chance to be served in softirq context sometimes.

The reason of lazy_list was not served is because the nearest activated
timer might have been set to expire after long time (such as 100+ seconds).
Then function run_local_timers() would not call raise_softirq(TIMER_SOFTIRQ)
to handle enqueued irq_work.

This is observed on LX2160ARDB and LS1088ARDB with cpufreq governor of
‘schedutil’ or ‘ondemand’.

Configure related irqwork to run on raw-irq context could fix this issue.

Signed-off-by: Ran Wang <redacted>
---
Change in v2:
 - Update commit message to explain root cause more clear.

 drivers/cpufreq/cpufreq_governor.c | 2 +-
 kernel/sched/cpufreq_schedutil.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_governor.c b/drivers/cpufreq/cpufreq_governor.c
index 63f7c219062b..731a7b1434df 100644
--- a/drivers/cpufreq/cpufreq_governor.c
+++ b/drivers/cpufreq/cpufreq_governor.c

@@ -360,7 +360,7 @@ static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *poli
 	policy_dbs->policy = policy;
 	mutex_init(&policy_dbs->update_mutex);
 	atomic_set(&policy_dbs->work_count, 0);
-	init_irq_work(&policy_dbs->irq_work, dbs_irq_work);
+	policy_dbs->irq_work = IRQ_WORK_INIT_HARD(dbs_irq_work);
 	INIT_WORK(&policy_dbs->work, dbs_work_handler);
 
 	/* Set policy_dbs for all CPUs, online+offline */

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 50cbad89f7fa..1d5af87ec92e 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c

@@ -611,7 +611,7 @@ static int sugov_kthread_create(struct sugov_policy *sg_policy)
 
 	sg_policy->thread = thread;
 	kthread_bind_mask(thread, policy->related_cpus);
-	init_irq_work(&sg_policy->irq_work, sugov_irq_work);
+	sg_policy->irq_work = IRQ_WORK_INIT_HARD(sugov_irq_work);
 	mutex_init(&sg_policy->work_lock);
 
 	wake_up_process(thread);