[PATCH v2 2/3] x86/irq: Use irq_chip_retrigger_hierarchy() in fixup_irqs()

fixup_irqs() re-injects a pending interrupt on its new target CPU by
looking at the outermost domain chip and invoking its irq_retrigger()
callback directly. That only works when the outermost chip happens to
install an irq_retrigger() callback, which is not guaranteed for every
irqchip and could lead to lost interrupts on CPU hot-unplug.

Use irq_chip_retrigger_hierarchy() instead, which walks up the interrupt
hierarchy until it finds a chip that implements irq_retrigger().

While at it, move the loop-local variables into the loop scope and use a
scoped guard for desc->lock.

VECTOR_RETRIGGERED is now set only when the retrigger succeeds
(irq_chip_retrigger_hierarchy() returns non-zero) instead of
unconditionally. This is harmless today since apic_retrigger_irq()
always returns 1, and arguably more correct. No functional change
intended for chips which already provide an irq_retrigger() callback
on the outermost domain.

Suggested-by: Thomas Gleixner <[email protected]>
Reviewed-by: Shradha Gupta <[email protected]>
Signed-off-by: Naman Jain <[email protected]>
---
 arch/x86/kernel/irq.c | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 30122f0b3af96..ef1bdd3c4659a 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -466,11 +466,6 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_posted_msi_notification)
 /* A cpu has been removed from cpu_online_mask.  Reset irq affinities. */
 void fixup_irqs(void)
 {
-	unsigned int vector;
-	struct irq_desc *desc;
-	struct irq_data *data;
-	struct irq_chip *chip;
-
 	irq_migrate_all_off_this_cpu();
 
 	/*
@@ -489,22 +484,18 @@ void fixup_irqs(void)
 	 * vector_lock because the cpu is already marked !online, so
 	 * nothing else will touch it.
 	 */
-	for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
-		if (IS_ERR_OR_NULL(__this_cpu_read(vector_irq[vector])))
+	for (unsigned int vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
+		struct irq_desc *desc = __this_cpu_read(vector_irq[vector]);
+
+		if (IS_ERR_OR_NULL(desc))
 			continue;
 
 		if (is_vector_pending(vector)) {
-			desc = __this_cpu_read(vector_irq[vector]);
-
-			raw_spin_lock(&desc->lock);
-			data = irq_desc_get_irq_data(desc);
-			chip = irq_data_get_irq_chip(data);
-			if (chip->irq_retrigger) {
-				chip->irq_retrigger(data);
+			guard(raw_spinlock)(&desc->lock);
+			if (irq_chip_retrigger_hierarchy(&desc->irq_data))
 				__this_cpu_write(vector_irq[vector], VECTOR_RETRIGGERED);
-			}
-			raw_spin_unlock(&desc->lock);
 		}
+
 		if (__this_cpu_read(vector_irq[vector]) != VECTOR_RETRIGGERED)
 			__this_cpu_write(vector_irq[vector], VECTOR_UNUSED);
 	}
-- 
2.43.0