From: Thomas Gleixner <tglx@kernel.org>
Date: Sun, 17 May 2026 20:02:34 +0000 (+0200)
Subject: genirq: Add rcuref count to struct irq_desc
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1d9c4745bfb6773712751f5068c23ebad9cd30a0;p=thirdparty%2Flinux.git

genirq: Add rcuref count to struct irq_desc

Prepare for a smarter iterator for /proc/interrupts so that the next
interrupt descriptor can be cached after lookup.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Dmitry Ilvokhin <d@ilvokhin.com>
Link: https://patch.msgid.link/20260517194931.917415190@kernel.org
---

diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index 1058786d76ebb..8080db17c1b1b 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -70,6 +70,7 @@ struct irq_redirect {
  *			IRQF_NO_SUSPEND set
  * @force_resume_depth:	number of irqactions on a irq descriptor with
  *			IRQF_FORCE_RESUME set
+ * @refcnt:		Reference count mainly for /proc/interrupts
  * @rcu:		rcu head for delayed free
  * @kobj:		kobject used to represent this struct in sysfs
  * @request_mutex:	mutex to protect request/free before locking desc->lock
@@ -119,6 +120,7 @@ struct irq_desc {
 	struct dentry		*debugfs_file;
 	const char		*dev_name;
 #endif
+	rcuref_t		refcnt;
 #ifdef CONFIG_SPARSE_IRQ
 	struct rcu_head		rcu;
 	struct kobject		kobj;
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index be702dd64422b..bacbf4020242f 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -9,6 +9,7 @@
 #include <linux/irqdesc.h>
 #include <linux/kernel_stat.h>
 #include <linux/pm_runtime.h>
+#include <linux/rcuref.h>
 #include <linux/sched/clock.h>
 
 #ifdef CONFIG_SPARSE_IRQ
@@ -101,9 +102,23 @@ extern void unmask_irq(struct irq_desc *desc);
 extern void unmask_threaded_irq(struct irq_desc *desc);
 
 #ifdef CONFIG_SPARSE_IRQ
-static inline void irq_mark_irq(unsigned int irq) { }
+static __always_inline void irq_mark_irq(unsigned int irq) { }
+void irq_desc_free_rcu(struct irq_desc *desc);
+
+static __always_inline bool irq_desc_get_ref(struct irq_desc *desc)
+{
+	return rcuref_get(&desc->refcnt);
+}
+
+static __always_inline void irq_desc_put_ref(struct irq_desc *desc)
+{
+	if (rcuref_put(&desc->refcnt))
+		irq_desc_free_rcu(desc);
+}
 #else
 extern void irq_mark_irq(unsigned int irq);
+static __always_inline bool irq_desc_get_ref(struct irq_desc *desc) { return true; }
+static __always_inline void irq_desc_put_ref(struct irq_desc *desc) { }
 #endif
 
 irqreturn_t __handle_irq_event_percpu(struct irq_desc *desc);
diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
index 90595eefb4779..23f21763bfed7 100644
--- a/kernel/irq/irqdesc.c
+++ b/kernel/irq/irqdesc.c
@@ -137,6 +137,7 @@ static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node,
 	desc->tot_count = 0;
 	desc->name = NULL;
 	desc->owner = owner;
+	rcuref_init(&desc->refcnt, 1);
 	desc_smp_init(desc, node, affinity);
 }
 
@@ -465,6 +466,17 @@ static void delayed_free_desc(struct rcu_head *rhp)
 	kobject_put(&desc->kobj);
 }
 
+void irq_desc_free_rcu(struct irq_desc *desc)
+{
+	/*
+	 * We free the descriptor, masks and stat fields via RCU. That
+	 * allows demultiplex interrupts to do rcu based management of
+	 * the child interrupts.
+	 * This also allows us to use rcu in kstat_irqs_usr().
+	 */
+	call_rcu(&desc->rcu, delayed_free_desc);
+}
+
 static void free_desc(unsigned int irq)
 {
 	struct irq_desc *desc = irq_to_desc(irq);
@@ -483,14 +495,7 @@ static void free_desc(unsigned int irq)
 	 */
 	irq_sysfs_del(desc);
 	delete_irq_desc(irq);
-
-	/*
-	 * We free the descriptor, masks and stat fields via RCU. That
-	 * allows demultiplex interrupts to do rcu based management of
-	 * the child interrupts.
-	 * This also allows us to use rcu in kstat_irqs_usr().
-	 */
-	call_rcu(&desc->rcu, delayed_free_desc);
+	irq_desc_put_ref(desc);
 }
 
 static int alloc_descs(unsigned int start, unsigned int cnt, int node,