Merge: workqueue: Avoid using isolated cpus' timers on queue_delayed_work

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/3781

JIRA: https://issues.redhat.com/browse/RHEL-20254

Tested: oslat test on host & guest VM

Upstream Status: https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git/

Improves latency for host & guest RT tasks running on isolated CPUs.
- Avoid usage of isolated CPU to handle timer interrupts on schedule_delayed_work().

Signed-off-by: Leonardo Bras <leobras@redhat.com>

Approved-by: Waiman Long <longman@redhat.com>
Approved-by: Marcelo Tosatti <mtosatti@redhat.com>

Merged-by: Lucas Zampieri <lzampier@redhat.com>

Author: zampierilucas

kernel/workqueue.c

@@ -1677,10 +1677,18 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
 	dwork->cpu = cpu;
 	timer->expires = jiffies + delay;
 
-	if (unlikely(cpu != WORK_CPU_UNBOUND))
+	if (housekeeping_enabled(HK_TYPE_TIMER)) {
+		/* If the current cpu is a housekeeping cpu, use it. */
+		cpu = smp_processor_id();
+		if (!housekeeping_test_cpu(cpu, HK_TYPE_TIMER))
+			cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
 		add_timer_on(timer, cpu);
-	else
-		add_timer(timer);
+	} else {
+		if (likely(cpu == WORK_CPU_UNBOUND))
+			add_timer(timer);
+		else
+			add_timer_on(timer, cpu);
+	}
 }
 
 /**