genirq/chip: Rework handle_nested_irq()

Use the new helpers to decide whether the interrupt should be handled and
switch the descriptor locking to guard().

Fixup the kernel doc comment while at it.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20250429065420.744042890@linutronix.de

Author: KAGA-KOKO

kernel/irq/chip.c

@@ -450,48 +450,6 @@ void unmask_threaded_irq(struct irq_desc *desc)
 	unmask_irq(desc);
 }
 
-/*
- *	handle_nested_irq - Handle a nested irq from a irq thread
- *	@irq:	the interrupt number
- *
- *	Handle interrupts which are nested into a threaded interrupt
- *	handler. The handler function is called inside the calling
- *	threads context.
- */
-void handle_nested_irq(unsigned int irq)
-{
-	struct irq_desc *desc = irq_to_desc(irq);
-	struct irqaction *action;
-	irqreturn_t action_ret;
-
-	might_sleep();
-
-	raw_spin_lock_irq(&desc->lock);
-
-	desc->istate &= ~(IRQS_REPLAY | IRQS_WAITING);
-
-	action = desc->action;
-	if (unlikely(!action || irqd_irq_disabled(&desc->irq_data))) {
-		desc->istate |= IRQS_PENDING;
-		raw_spin_unlock_irq(&desc->lock);
-		return;
-	}
-
-	kstat_incr_irqs_this_cpu(desc);
-	atomic_inc(&desc->threads_active);
-	raw_spin_unlock_irq(&desc->lock);
-
-	action_ret = IRQ_NONE;
-	for_each_action_of_desc(desc, action)
-		action_ret |= action->thread_fn(action->irq, action->dev_id);
-
-	if (!irq_settings_no_debug(desc))
-		note_interrupt(desc, action_ret);
-
-	wake_threads_waitq(desc);
-}
-EXPORT_SYMBOL_GPL(handle_nested_irq);
-
 static bool irq_check_poll(struct irq_desc *desc)
 {
 	if (!(desc->istate & IRQS_POLL_INPROGRESS))
@@ -543,6 +501,42 @@ static inline bool irq_can_handle(struct irq_desc *desc)
 	return irq_can_handle_actions(desc);
 }
 
+/**
+ * handle_nested_irq - Handle a nested irq from a irq thread
+ * @irq:	the interrupt number
+ *
+ * Handle interrupts which are nested into a threaded interrupt
+ * handler. The handler function is called inside the calling threads
+ * context.
+ */
+void handle_nested_irq(unsigned int irq)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+	struct irqaction *action;
+	irqreturn_t action_ret;
+
+	might_sleep();
+
+	scoped_guard(raw_spinlock_irq, &desc->lock) {
+		if (irq_can_handle_actions(desc))
+			return;
+
+		action = desc->action;
+		kstat_incr_irqs_this_cpu(desc);
+		atomic_inc(&desc->threads_active);
+	}
+
+	action_ret = IRQ_NONE;
+	for_each_action_of_desc(desc, action)
+		action_ret |= action->thread_fn(action->irq, action->dev_id);
+
+	if (!irq_settings_no_debug(desc))
+		note_interrupt(desc, action_ret);
+
+	wake_threads_waitq(desc);
+}
+EXPORT_SYMBOL_GPL(handle_nested_irq);
+
 /**
  *	handle_simple_irq - Simple and software-decoded IRQs.
  *	@desc:	the interrupt description structure for this irq