linux-kernel - [RFC PATCH v2] genirq/cpuhotpug: notify of irq affinity change for offlined cpu.

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Message-Id: <20260102165308.76290-1-imran.f.khan@oracle.com>
Date: Sat,  3 Jan 2026 00:53:08 +0800
From: Imran Khan <imran.f.khan@...cle.com>
To: tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org
Subject: [RFC PATCH v2] genirq/cpuhotpug: notify of irq affinity change for offlined cpu.

During cpu offlining the irqs with broken_affinity are affined
to other CPU but this affinity change is not accounted for by
desc::affinity_notify (if available).
This can leave users of irq_set_affinity_notifier, with old
affinity information.

Signed-off-by: Imran Khan <imran.f.khan@...cle.com>
---
v1 -> v2:
 - Fix compilation error due to missed parenthesis around scoped_guard

 kernel/irq/cpuhotplug.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index 755346ea98196..30153be1a4cca 100644
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -177,9 +177,17 @@ 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_irqsave, &desc->lock) {
 			affinity_broken = migrate_one_irq(desc);
-
+			if (affinity_broken && 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 (affinity_broken) {
 			pr_debug_ratelimited("IRQ %u: no longer affine to CPU%u\n",
 					    irq, smp_processor_id());

base-commit: f8f9c1f4d0c7a64600e2ca312dec824a0bc2f1da
-- 
2.34.1