Re: 3.18.7-rt2: NOHZ_FULL warning at boot

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

* Luis Claudio R. Goncalves | 2015-02-26 17:05:47 [-0300]:

>I have been seeing the warning below at boot time on 3.18.7-rt2. Anybody
>else seeing it?

This should fix it.

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 19c363a..0c64912 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -71,6 +71,8 @@ void __weak arch_irq_work_raise(void)
  */
 bool irq_work_queue_on(struct irq_work *work, int cpu)
 {
+	bool raise_irqwork;
+
 	/* All work should have been flushed before going offline */
 	WARN_ON_ONCE(cpu_is_offline(cpu));
 
@@ -81,7 +83,19 @@ bool irq_work_queue_on(struct irq_work *work, int cpu)
 	if (!irq_work_claim(work))
 		return false;
 
-	if (llist_add(&work->llnode, &per_cpu(raised_list, cpu)))
+#ifdef CONFIG_PREEMPT_RT_FULL
+	if (work->flags & IRQ_WORK_HARD_IRQ)
+		raise_irqwork = llist_add(&work->llnode,
+					  &per_cpu(hirq_work_list, cpu));
+	else
+		raise_irqwork = llist_add(&work->llnode,
+					  &per_cpu(lazy_list, cpu));
+#else
+		raise_irqwork = llist_add(&work->llnode,
+					  &per_cpu(raised_list, cpu));
+#endif
+
+	if (raise_irqwork)
 		arch_send_call_function_single_ipi(cpu);
 
 	return true;
@@ -101,19 +115,14 @@ bool irq_work_queue(struct irq_work *work)
 
 #ifdef CONFIG_PREEMPT_RT_FULL
 	if (work->flags & IRQ_WORK_HARD_IRQ) {
-		if (llist_add(&work->llnode, this_cpu_ptr(&hirq_work_list))) {
-			if (work->flags & IRQ_WORK_LAZY) {
-				if (tick_nohz_tick_stopped())
-					arch_irq_work_raise();
-			} else {
-				arch_irq_work_raise();
-			}
-		}
-	/* If the work is "lazy", handle it from next tick if any */
-	} else if (work->flags & IRQ_WORK_LAZY) {
+		if (llist_add(&work->llnode, this_cpu_ptr(&hirq_work_list)))
+			arch_irq_work_raise();
+	} else {
+		if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)))
+			arch_irq_work_raise();
+	}
 #else
 	if (work->flags & IRQ_WORK_LAZY) {
-#endif
 		if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
 		    tick_nohz_tick_stopped())
 			arch_irq_work_raise();
@@ -121,6 +130,7 @@ bool irq_work_queue(struct irq_work *work)
 		if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))
 			arch_irq_work_raise();
 	}
+#endif
 
 	preempt_enable();
 
@@ -137,7 +147,8 @@ bool irq_work_needs_cpu(void)
 
 	if (llist_empty(raised))
 		if (llist_empty(lazy))
-			return false;
+			if (llist_empty(this_cpu_ptr(&hirq_work_list)))
+				return false;
 
 	/* All work should have been flushed before going offline */
 	WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));

Sebastian