genirq: Move clear of kstat_irqs to free_desc()

desc_set_defaults() has a loop to clear the per-cpu counters kstats_irq.

This is only needed in free_desc(), which is used with non-sparse IRQs so
that the interrupt descriptor can be recycled. For newly allocated
descriptors, the memory comes from alloc_percpu() and is already zeroed
out.

Move the loop to free_desc() to avoid wasting time unnecessarily.

Signed-off-by: Luigi Rizzo <lrizzo@google.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260112083234.2665832-1-lrizzo@google.com

Author: Luigi Rizzo

kernel/irq/irqdesc.c

@@ -115,8 +115,6 @@ static inline void free_masks(struct irq_desc *desc) { }
 static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node,
 			      const struct cpumask *affinity, struct module *owner)
 {
-	int cpu;
-
 	desc->irq_common_data.handler_data = NULL;
 	desc->irq_common_data.msi_desc = NULL;
 
@@ -134,8 +132,6 @@ static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node,
 	desc->tot_count = 0;
 	desc->name = NULL;
 	desc->owner = owner;
-	for_each_possible_cpu(cpu)
-		*per_cpu_ptr(desc->kstat_irqs, cpu) = (struct irqstat) { };
 	desc_smp_init(desc, node, affinity);
 }
 
@@ -621,9 +617,14 @@ EXPORT_SYMBOL(irq_to_desc);
 static void free_desc(unsigned int irq)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
+	int cpu;
 
 	scoped_guard(raw_spinlock_irqsave, &desc->lock)
 		desc_set_defaults(irq, desc, irq_desc_get_node(desc), NULL, NULL);
+
+	for_each_possible_cpu(cpu)
+		*per_cpu_ptr(desc->kstat_irqs, cpu) = (struct irqstat) { };
+
 	delete_irq_desc(irq);
 }