linux-kernel - [PATCH v3] genirq/cpuhotplug: notify about irq affinity change for offlined cpus.

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Message-Id: <20260113143727.1041265-1-imran.f.khan@oracle.com>
Date: Tue, 13 Jan 2026 22:37:27 +0800
From: Imran Khan <imran.f.khan@...cle.com>
To: tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH v3] genirq/cpuhotplug: notify about irq affinity change for offlined cpus.

During cpu offlining the irqs affined to that cpu are moved
to other cpu, but this affinity change is not accounted for by
irq_desc::affinity_notify (if available).
This can leave users, of irq_set_affinity_notifier, with old
affinity information.
Avoid this by allowing to schedule affinity change notification
work for irqs that were affined to the cpu being offlined.

Also since irq_set_affinity_locked uses the same logic to
schedule affinity change notification work, split out this
logic in a dedicated function and use that at both the places.

Signed-off-by: Imran Khan <imran.f.khan@...cle.com>
---
v2 -> v3:
 - Address review comments from Thomas
 - Removed RFC tag
v1 -> v2:
 - Fix compilation error due to missed parenthesis around scoped_guard

 include/linux/interrupt.h |  2 ++
 kernel/irq/cpuhotplug.c   |  6 ++++--
 kernel/irq/manage.c       | 28 ++++++++++++++++++++--------
 3 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 266f2b39213a0..6f93bf524f728 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -383,6 +383,7 @@ irq_create_affinity_masks(unsigned int nvec, struct irq_affinity *affd);
 unsigned int irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
 				       const struct irq_affinity *affd);
 
+extern void schedule_affinity_notify_work(struct irq_desc *desc);
 #else /* CONFIG_SMP */
 
 static inline int irq_set_affinity(unsigned int irq, const struct cpumask *m)
@@ -445,6 +446,7 @@ irq_calc_affinity_vectors(unsigned int minvec, unsigned int maxvec,
 	return maxvec;
 }
 
+static inline void schedule_affinity_notify_work(struct irq_desc *desc) { }
 #endif /* CONFIG_SMP */
 
 /*
diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index 755346ea98196..c77a3b95fba85 100644
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -177,9 +177,11 @@ void irq_migrate_all_off_this_cpu(void)
 		bool affinity_broken;
 
 		desc = irq_to_desc(irq);
-		scoped_guard(raw_spinlock, &desc->lock)
+		scoped_guard(raw_spinlock, &desc->lock) {
 			affinity_broken = migrate_one_irq(desc);
-
+			if (affinity_broken && desc->affinity_notify)
+				schedule_affinity_notify_work(desc);
+		}
 		if (affinity_broken) {
 			pr_debug_ratelimited("IRQ %u: no longer affine to CPU%u\n",
 					    irq, smp_processor_id());
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 349ae7979da0e..6440a64f65a7b 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -139,6 +139,23 @@ void synchronize_irq(unsigned int irq)
 }
 EXPORT_SYMBOL(synchronize_irq);
 
+/**
+ * schedule_affinity_notify_work - Schedule work to notify
+ * about irq affinity change.
+ * @desc:  irq descriptor whose affinity changed
+ *
+ * Caller needs to hold desc->lock
+ */
+void schedule_affinity_notify_work(struct irq_desc *desc)
+{
+	kref_get(&desc->affinity_notify->kref);
+	if (!schedule_work(&desc->affinity_notify->work))
+		/* Work was already scheduled, drop our extra ref */
+		kref_put(&desc->affinity_notify->kref,
+			 desc->affinity_notify->release);
+}
+EXPORT_SYMBOL_GPL(schedule_affinity_notify_work);
+
 #ifdef CONFIG_SMP
 cpumask_var_t irq_default_affinity;
 
@@ -367,14 +384,9 @@ int irq_set_affinity_locked(struct irq_data *data, const struct cpumask *mask,
 		irq_copy_pending(desc, mask);
 	}
 
-	if (desc->affinity_notify) {
-		kref_get(&desc->affinity_notify->kref);
-		if (!schedule_work(&desc->affinity_notify->work)) {
-			/* Work was already scheduled, drop our extra ref */
-			kref_put(&desc->affinity_notify->kref,
-				 desc->affinity_notify->release);
-		}
-	}
+	if (desc->affinity_notify)
+		schedule_affinity_notify_work(desc);
+
 	irqd_set(data, IRQD_AFFINITY_SET);
 
 	return ret;

base-commit: f8f9c1f4d0c7a64600e2ca312dec824a0bc2f1da
-- 
2.34.1